small 1/4mile oval tips, transitioning from road racing

[rob burgoon]

My local track is Barona Speedway near San Diego, a small 1/4 mile oval. I've an IMCA mod with a 602 in it. I've been fairly successful in sports cars on asphalt road courses (Laguna, Sears, etc), and have read a book about 4 bar rear suspensions, but I'm still having some issues with knowing how the car is supposed to handle.

Has anyone else transitioned from sports car racing? How is the car supposed to feel? Should I be tossing the car in sideways with a "pitch and catch" technique? Should the car want to do the entry on its own without me tossing it in there? Do you guys rely on trail braking to get rotation on entry?

Sorry if the questions are vague, I'm not really sure what question I should be asking.

Would anyone be willing to share how the setup and driving style changes from say your average 3/8 oval to a small semi-banked 1/4 mile track?

[RRR_Products]

My local track is Barona Speedway near San Diego, a small 1/4 mile oval.I've an IMCA mod with a 602 in it. I've been fairly successful in sports cars on asphalt road courses (Laguna, Sears, etc), and have read a book about 4 bar rear suspensions, but I'm still having some issues with knowing how the car is supposed to handle. Has anyone else transitioned from sports car racing? How is the car supposed to feel? Should I be tossing the car in sideways with a "pitch and catch" technique? Should the car want to do the entry on its own without me tossing it in there? Do you guys rely on trail braking to get rotation on entry?Sorry if the questions are vague, I'm not really sure what question I should be asking.Would anyone be willing to share how the setup and driving style changes from say your average 3/8 oval to a small semi-banked 1/4 mile track? p.s. anyone know why all my newlines vanished when I hit submit?Hey Rob will you be at this track this Saturday? Give me a private message and I'll work with you on this.

[TS3g]

I have no asphalt/road experience, but I will tell you that you drive a dirt car more with your feet than the steering wheel. A properly setup car should naturally want to to start turning off throttle on corner entry. Most people trail brake of some sort to control the pitchiness of the entry, trail brake more to tighten entry, less to let it rotate on its own. And by trail brake, I mean apply the brakes and gas at same time as I seem to recall road racers used trail braking terminology differently.

With a modified, it is paramount to pick up the gas early after corner entry (apply just a little throttle, don't stab it unless the car is super tight and track is heavy) to get the car on the bars. This will lock the car down (stop sliding) and let you rotate through the center while starting to accelerate. Apply only as much throttle as the track will allow at any time, although with a 602 and 4 bar, you should be able to be pretty aggressive.

Track to track setups shouldn't change much if you find a good baseline setup, typically a bar angle/possibly spring change is all. Being new to mods, I would advise having someone hot lap the car for you to make sure it is setup closely, then just concentrate on driving it as much as possible without making a lot of setup changes. You can dial yourself out of the ballpark incredibly easy with these cars, so it would be best to learn to drive it first, then tackle setups later. Welcome to dirt racing, have fun!

[rob burgoon]

Probably not driving tomorrow, still have some welding to do.

Thanks TS3g, sports car folks call any brake/steering overlap trail braking. Good to know it's different.So you pick up the gas midcorner to get on the bars which reduces rotation? Then add as much gas as you can without getting excessive rotation?

I've got some on board video here:http://youtu.be/fAuoYbM-oWI?list=UUC_thJguPLlar7QdjNkNbSQ

same race from the stands here:http://youtu.be/DW3e2IRhsko?list=UUC_thJguPLlar7QdjNkNbSQ

daytime here:http://youtu.be/2RA710EqdGI?list=UUC_thJguPLlar7QdjNkNbSQ

See anything obviously wrong with technique or setup?

[RRR_Products]

Hey Rob we spoke last year during a practice session. I think I gave you my card and we talked about the road course schools I teach at and how to smooth things out on track relating to the road course driving you've done. I believe on the clock you were almost a full second faster and unlike the other sessions no spins! You ever get that lr slider fixed? Anyways keep in touch and I'll be in town Saturday night.

[rob burgoon]

Thanks for the help RRR, but I'm not looking for professional coaching at this time.

[JustAddDirt]

first thing I see/hear, is the car needs more gear.
that will help with corner entry as well. sounds like you are on brakes a good bit.
I know it is a crate motor, but it needs to turn more than 5k rpms.
It sounds like motor is starting to come on power mid straightaway, and then you are off the throttle.

[charcoal01]

I've run baron a few times before so I might be able to help a bit. My home track is cocopah but I raced my pro stock there and had a few 2nds and 3rds. I only ran my mod once because I think the track is too small and they farm it too much for my taste. That's neither here nor there I guess so any ways, what gear are you running and what kind of car and rear suspension? Also, what ratio is your steering? Are you running a 602 or 604 crate?

[save the racers]

Also, what ratio is your steering? I was wondering this as well. It looks like the car is darty or driver is not used to that quick of steering. Have you tried more toe out?

[rob burgoon]

602, 4.7 rear gear, 4 bar rear, no idea on the steering ratio, driver is used to unpowered rack and pinion on asphalt.There's not a lot of room for my right elbow, so it seems like I end up one handing the wheel with my left when the inputs get big.

[JustAddDirt]

that is a small track.
probably needs to be a 6.00-6.20 rear end gear. (judging by videos)
Check toe out, set it at .5"
Seat time will help getting used to the steering.
I think a rear end gear change will help a lot.

[rob burgoon]

I noticed that the RF spring is only 650. I'm changing to an 850 spring to see if I can get the car to oversteer less in mid and exit. I do have a 6.2 rear gear that I can try, but won't that be way short? The redline on this crate is only 5500rpm. My suspicion is that once I get this car handling well, the speeds will go up and the gear will be much closer.

[JustAddDirt]

I believe the 850 will be way too much RF spring on that small of a track.
It sounds like the car may be a bit tight ( and that gear does not help matters) and you are burping throttle to try to get it to turn. then the car goes loose. car does not know what to do.
On corner entry once you turn car into corner to get the car to stay consistent through corner, it would be best to stay at one point on the throttle, and increase throttle through middle to exit.
If car is too tight (understeer) then you need a tick more stagger or some 4-link adjustments.
If car is loose (oversteer) you may need to take out stagger or some 4-link adjustments.
as for the gearing, the way it sounds on the in car videos the car does not start to hit its power range till mid straightaway, and then you are off the throttle.
You said gear was a 4.70?

[rob burgoon]

Tried the 850, didn't seem to make any difference that I could feel. Tach was hitting about 5,000rpm with bad handling, redline is 5,500rpm.Tried zeroing out the stagger, didn't help.I put the car on scales, and left side is 51%, rear is 54%, bite is -70.How bad is it having a bite of -70?Left side ride height of 5", right side is 7".RF UBJ is 1/2" shorter than LF UBJ.Burned up the RR pretty bad. Think the bite is the problem?

[oldtrackchamp4x]

Left side is a couple percent low, rear should be close to 55.5- 56.5 scaled at end of feature. You say you have 70# rr bite! Should be about 70-90# lr bite with you out of car.I'll bet you had fun with bad handling. JMO

[rob burgoon]

Ok, made a bunch of changes. In the past I had raised the chassis mount of the J bar without adjusting length. I put the J bar back down to about 7" (I think). Lowered the right side ride height to 6". Changed the bite from -70 to +10. Left the 850 RF spring in place. Changed the RF UBJ to a +1/2" model. These changes should lower the rear roll center and raise the front roll center, and hopefully tighten the car up.

RR was a little worn so I put some sipes in what was left and did a test day.

At the test day the first 5 min session was good (but that session is always good since the dirt is softer). The second session wasn't amazing, but seemed to be better than two weeks ago. The car was worse in the next session, got out and saw the RR had corded. Put the spare on the RR and the car seemed "not terrible" in the next session, got into the rev limiter a few times (5500rpm), then it went to crap again in the next session or two. Noticed I had corded the LR and was out of tires so went home.

I would have liked to have swapped the left side tires to put the bad one up front to see how that felt. Also if the tires were a little more stable in life, I would have tried changing the cross weight to see if I could eliminate mild to moderate looseness from mid to exit.

Conditions started out as lightly watered dirt that was good for sliding in, then shortly after the dirt seemed to pack, get hard, and a black ribbon appeared that only got wider. As the track blacked over, holding a slide got harder and harder and towards the end I was experimenting with driving straight in hard and thinking about shifting brake bias forwards. The rear tires were conking out as well, so perhaps that played into it. Tire temps were 145-150*F across both front tires, 190*F on rears. I was going down most straights sideways the length of the straight.

[rob burgoon]

Under car video here:
http://www.youtube.com/watch?v=EjwDOwqpDdQThe

LR appears to be bottoming out on a tube, I think I need to add a droop chain or strap so the tube doesn't get beaten up further. Anyone know where those are for sale or what they are usually called?

[Bcollins82]

I think you should start off by listening really, really close to what Just Add Dirt says. You are getting info from one of the fastest guys in the country, you should pay very close attention to the advice you get from him. You are hitting the chip because you are spinning the tires.... Start with a gear change that gets you in the ballpark. A 4.70 on a 1/4 mile is not in the ballpark. Take the 850 out of the RF, its keeping you from getting over on the RF and letting the LR travel to add drive and sidebite. Im not sure where you are measuring your ride height from, but normally the right side is lower than the left. 2" higher on the right side is a ton of tilt the wrong direction. As a rule of thumb, center of balljoint level with center of the RF inner pivot bolt of the lower control arm, left side inner pivot bolt 1/4" higher than the right, and 1" of rake from front to rear measured at the bottom of the front crossmember to the bottom of the framerail on the RR in front of the lower link mounts. Thats not exact, but will get you close. Also, from your under car video, you need to change the LR underrail bar because its not letting the LR travel enough. Adding a limit chain to stop it shorter will make your problems worse. Limit chains are good, and a great tuning tool. Set up a limit chain thats adjustable once you get the underrail dropped so your suspension travel isn't being limited by it. My advice to you is to start by taking the car to someone that understands how a dirt car works, and is fast in your area. Let them go through the car and get it right, and explain to you why they are making the changes. Once the car is closer you will be able to concentrate on driving more, and making small tuning changes to the chassis and tires. Good luck!

[oldtrackchamp4x]

Agree with 82. Also if you know who built your chassis, call them and they will get you dialed in on setup if no one will help you.Get a baseline setup and drive the car like the fast guys at your track drive since you are just starting out on dirt. Don't slide the car. Finally, ONLY MAKE ONE CHANGE AT A TIME. JMO.

[rob burgoon]

My engine makes 350hp and reds at 5500. If you divide your highest not spinning RPM by diff ratio, you get rear axle RPM. People I race against are at about 1200 axle rpm at the end of the straight. My rear axle rpm at redline is 5,500/4.7 1170rpm. It's already geared a little short, so when you guys say to shorten it way further, it sounds like crazytalk.

The LR underrail is a welded in tube, I'd have to get aggressive to lower it. The rear upper bar currently sees 42* at full droop. That's in the ballpark, right?

The car is a dirtworks from the 90s. I have what I believe to be the factory setup guide, and my flurry of changes all brought the car back towards baseline (big RF spring included).

Ride height measured from where the frame moves out a foot behind the front "wheel wheel", and where the frame rail stops before the rear "wheel well" (as described in the old dirt works setup guide).

I'm not saying I don't believe you guys when you say that 850 is too much, right now I'd be giddy if I could feel a push just once while the throttle is on, so I'm screwing around to see if I can get that. Since 850 is in the setup guide, I figured why not.

[rob burgoon]

"Take the 850 out of the RF, its keeping you from getting over on the RF and letting the LR travel to add drive and sidebite."

bcollins, let's dig into this a little if you don't mind.

Let say I soften RF from 850 to 650. On entry the car will rock further towards the RF, drooping the LR a little. However, mid corner, the softer RF means more weight from body roll on the RR which can overload the RR causing oversteer.

How does a softer RF create drive and sidebite at mid and exit? Seems like it does the opposite.

[Bcollins82]

"Take the 850 out of the RF, its keeping you from getting over on the RF and letting the LR travel to add drive and sidebite."

bcollins, let's dig into this a little if you don't mind.

Let say I soften RF from 850 to 650. On entry the car will rock further towards the RF, drooping the LR a little. However, mid corner, the softer RF means more weight from body roll on the RR which can overload the RR causing oversteer.

How does a softer RF create drive and sidebite at mid and exit? Seems like it does the opposite.

I understand that the underrail bar is welded in. You are dealing with a chassis that was never designed to travel that far. Same as the ride heights, things are being done differently now. Cut that underrail and bend up a new one and weld it in... Don't worry, all older underrail cars have had this done. Bolt in sections work well also, just in case you don't go far enough the first time. Things have progressed, and even though it may have been designed for it then, it doesn't mean its the best way to do it now. 42 degrees at full drop is close, I usually aim for 44* with both sides hanging, car up and level. Its the only way to do it consistently IMO, but its at 42* when dropped because it is probably starting at a steeper angle than most to begin with. Softening the RF by itself will not add forward drive or sidebite. It is part of a package most cars are running now that uses a softer RF to get the LR up easier, farther, and keeping it up. Dynamic bar angle in the LR also seems to load the LR harder than stiffening the RF spring. And by letting the LR drop farther will raise the rear of the car, and that raises not only the LR bar angle, but also the weight, spoiler height, and adds J bar angle dynamically increasing drive and sidebite.

As far as the gear, you said it was hitting the chip more when you describe the track as dry and black and with the rear hung out all the way down the straight. That leads me to believe that you are hitting it by spinning the tires. 5500 rpm seems incredibly low for a limit. Is that really the high end safe RPM or is that just where power falls off?

[RRR_Products]

Hey Rob what springs do you have? We will def ditch the 850 though. Depending on the night you want to run dry vs tacky have a few springs available for the front end and let's see the valving on the shocks. Depending on what shocks are at or springs we can go from there. Throw a 175 in the RR and 200 LR. Don't recall if you have a brake floater or not on that car. Get rid of the LR under slung and put a strap on it. 4.5-5.5" drop you can start with. With the amount of power you're running you'll be fine on a dry night and tacky may struggle. Nothing wrong with less hp as most of the time too much can mask handling issues anyways. If I were to suggest where to start and what I know works well is a 750 RF and 550 LF in dry or if very dry also lighter RF but again the shock valving is something we would need to see. Just get a 550 LF though to start and get those shock numbers.

[rob burgoon]

Sounds good, looks like I'll be cutting the bar out and adding a droop chain soon then.

5,500 is where GM says to stop.

"RPM limits are critical to engine life. Catastrophic engine failure can occur if the engines are run
above the factory recommended limits. Extensive dyno & track testing has determined the limits of
the engine. Under no circumstances is it recommended to exceed these limits. GM recommends
that all sanctioning bodies, track operators or promoters have rev-limits written in their rule book.
Maximum limit for 602 engine is 5500 rpm."

If I was spinning the tires hard, I'd expect to zing the engine at corner exit when there's still a side load, not at the end of the straight when I am the most hooked up out of the entire lap. As the track got blacker, I was playing with a more diamond driving pattern and driving in deeper rather than trying to rotate early. (since sliding in became impractical). That might have extended the straight a little.

[oldtrackchamp4x]

Does the car have a metric or chevelle front clip? If it is chevelle then the 850 is way to stiff.JMO

[rob burgoon]

Does the car have a metric or chevelle front clip? If it is chevelle then the 850 is way to stiff.JMO

Chevelle I think, but I'm just guessing. What would the symptoms of a way too stiff RF be?

[rob burgoon]

602 crate produces nice useable power past 5500.. around here they run 6200 chip in them so they are chiping at approx. 6000.. just because the sticker from gm says 5500 doesn't mean that's the way to go.

Nice usable power is good. How long does the engine last going to 6k?

[rob burgoon]

Just checked droop on LR, 3 inches of droop travel.

[rob burgoon]

I see them for sale all the time around here 100 plus nights...

the speed limit is 55 on a lot of highways, you don't actually drive around at exactly 55 do you? same thing with gm sticker on these made in mexico motors.

Doesn't the strain on engine parts go up with the square or cube of RPM? My street car isn't at redline at 55mph!

But broken analogy aside, there's probably a safety margin to exploit. I'll consider upping the limiter instead of a gear change once we get the handling issues sorted and the speeds go up.

[charcoal01]

Many times I've dropped my total rpm by adding a taller gear, why? Because you're able to control wheel spin better and keep tires hooked up. I went to barona with my open motor ina mod and ran a 6.2 gear. You should be in the high fives at least.

[Bcollins82]

Just checked droop on LR, 3 inches of droop travel.

Thats not enough IMO... 4.5 to 5 is a good starting point. Make your limit chain adjustable, and don't just remove the underrail, replace it with one that is bent for clearance. Throw the original setup book in the garbage. Set the ride heights like I explained before, Take the spring out of the RF and cycle the suspension to be sure a 2" body shock will clear at full travel or you will junk shocks after you make the car travel. Youll probably want to add a couple degrees of camber to both sides (more pos on LF, neg on RF) since the car will roll more. Change the RF back to 650, LF to 750, LR 175 or 200, RR 225. Jbar in bottom hole on pinion, 5" of rake from center of pinion bolt to center of frame mount. A brake floater works well on this style setup if you arent using one already. Go up to 30 or 40 lbs of LR bite, add a couple percent of left side, and another percent rear. Post the rest of your full setup and include as much info as possible. Shock valving and location, bar lengths and angles, rearend square or trailing, wheel offsets, pullbar info including spring, and if possible a pic of each side the rear suspension LR pics at static and droop. There are a lot of great guys on here that will help if you are willing to give the info, and listen to what is being said.

[rob burgoon]

Many times I've dropped my total rpm by adding a taller gear, why? Because you're able to control wheel spin better and keep tires hooked up. I went to barona with my open motor ina mod and ran a 6.2 gear. You should be in the high fives at least.

Everyone here is saying my gearing (4.7) is too tall, not too short. You're telling me I need to go taller. High fives is shorter, not taller.

[charcoal01]

I'm sorry, for some reason I always screw that up. Shorter is the direction, not taller. Just a for instance, sport mods running a 602 at cocopah run almost the same gear as the a mods running open motors do.

[JustAddDirt]

rob burgoon

you are asking for assistance with a car. several have chimed in to offer advise. I being one of them.
1.You have an older car that was never designed to move like newer cars do. you need to have the option to go to 5" of drop on the lr. Frame will need to be altered to accommodate that. With that being said, you are basically lifting the LR tire off the racetrack when car does roll over with side bite.

2. You need to change the gear. I have 20 + years of dirt car experience, I know when a car needs a gear change.
you can say we are talking crazy talk, that is fine if you do not want to listen, that is your choice, we are just trying to assist. You might want to go ask some front runners what gear ratios they are running. By listening to your video, the competitor's are probably in the 5.67-6.0 range. Listen to their cars, and listen to yours. big difference in RPM's, and acceleration off the corners.
3. I would suggest you ask someone local for help, that has knowledge of dirt cars, and setups. Someone there is bound to assist you. even one of the frontrunners will probably help you. Just got to ask.
4. I would suggest a chassis seminar, if available in your area.
5. If you can upload photos of what the a arm angles (low front view),and some photos of the attitude of the car just sitting there from front and back, that will help us help you as well.

[rob burgoon]

2. You need to change the gear. I have 20 + years of dirt car experience, I know when a car needs a gear change.
you can say we are talking crazy talk, that is fine if you do not want to listen, that is your choice, we are just trying to assist. You might want to go ask some front runners what gear ratios they are running. By listening to your video, the competitor's are probably in the 5.67-6.0 range. Listen to their cars, and listen to yours. big difference in RPM's, and acceleration off the corners.

I feel like there is still some sort of misunderstanding here. My competitors are running claim engines. They can rev to nearly 8,000 rpm. I am the only person in my class using a 602, and I have chosen to believe GM when they say to set your limiter at 5,500.

With a 5,500 rpm limit, of course my car is going to sound different. It should.

I reach the limiter once in a while at the end of the straight. Unless you want me bouncing off the limiter down the straight, my gearing sounds correct. If my rears are spinning (I doubt they are), won't shorter gear ratios add torque and make the wheelspin worse?

[oldtrackchamp4x]

All i have to say is, don't ask questions if you aren't willing to listen to good advice. JMO

[rob burgoon]

All i have to say is, don't ask questions if you aren't willing to listen to good advice. I'm done. JMO

I'm sorry you feel that way, but asking for advice does not oblige me to blindly follow all that is given.

I have several books on dirt track setup and they disagree with each other on fundamental issues. The trick with the books is figuring out who knows what they are talking about.

[RRR_Products]

Rob revving 5500 will be just fine. Especially on a dry night there. If the car is too tight though it may be tougher to drive on a tacky night and may struggle. Also I know what spring set up works well at your track and the valving to get you in the ball park.

[charcoal01]

You're not taking into account the fact that lower hp generally needs more gear. You can keep believing that you only can run that 4.7 gear and you're going to keep struggling. Having an improperly geared dirt car can cause just as many issues as poor setup. Sportmod guys using 602's at cocopah run 5.14's and up and cocopah is almost twice the size of barona. You are spinning your wheels because something isn't right in your setup, you could probably get wheel spin with a set of 4.10s at that track.

[JustAddDirt]

I agree with charcoal01
Not to mention, lugging of an engine is worse than hitting the chip. You will probably end up spitting a rod out the side of the block, or a broken crank.

[rob burgoon]

I agree with charcoal01
Not to mention, lugging of an engine is worse than hitting the chip. You will probably end up spitting a rod out the side of the block, or a broken crank.

Lugging? At 3,000rpm? On a 602 crate? You can't be serious.

[rob burgoon]

You're not taking into account the fact that lower hp generally needs more gear. You can keep believing that you only can run that 4.7 gear and you're going to keep struggling. Having an improperly geared dirt car can cause just as many issues as poor setup. Sportmod guys using 602's at cocopah run 5.14's and up and cocopah is almost twice the size of barona. You are spinning your wheels because something isn't right in your setup, you could probably get wheel spin with a set of 4.10s at that track.

My counter argument is that at 80-90% of the lap around barona in dry conditions, a 600hp engine might as well be a 350hp engine when your ability to put down power is limited by small tires and slippery conditions.

How high are your sportmods overrevving the 602? Sportmod: 6,200/5.14=1206rpm. Me: 5,500/4.7=1170rpm. So I'm in the ballpark for cocopah. When I was looking into going to cocopah last winter, a friend told me the gear change between cocopah and barona wasn't large.

Maybe I'll install my gps logger to show real mph and rpm and settle this gearing disagreement one way or the other.

But to make progress here, let's assume for the moment that my gear is too tall and I'm spinning my tires hard. Fine. So the result of a gear change is more engine braking on the rear axle, and more torque everywhere.

Neither engine braking nor some extra torque are likely to change the handling of my car dramatically. Can we focus on changes that will?

I'll take some photos of the car's suspension with it on the ground.

Regarding dropping the under tube, if you're chain limited, is the under tube just there for stiffening the rear frame rail? Any shortcuts for someone who doesn't have a pipe bender?

[Confused?]

It's obvious that you already have your mind made up. Keep going as you are and when you get tired of getting lapped in the first part of the feature, maybe you will listen to some of the advice on here. Remember, YOU are the one that is new to modifieds and dirt tracks, not the people trying to help you.

[rob burgoon]

It's obvious that you already have your mind made up. Keep going as you are and when you get tired of getting lapped in the first part of the feature, maybe you will listen to some of the advice on here. Remember, YOU are the one that is new to modifieds and dirt tracks, not the people trying to help you.

Haven't been a lap down in years. Nice try though.

[charcoal01]

One of my friends was running a 5.29 gear with a 6200 chip at cocopah. I don't know why you're stuck on this 5500 number AS EVERYONE here with experience with crates tells you 6200 is perfectly safe. When I ran an open motor at cocopah I ran a 5.67 and when I ran barona I ran a 6.20 and probably would have run more if I had the gear. I'm ona crate now, run a 5.14 and probably would run a 5.67 or .83 if I ran barona again so whoever hold you the gear isn't much different doesn't know what they're talking about.

At barona you're literally completely on the gas for about a total of 3 seconds per lap, so 1) if you do hit the chip it's going to be so short ofa time it's not going to hurt a thing and 2) if you don't have enough gear to get off the corner your whole lap is screwed up because your corner entry speed is going to be slower, your weight transfer will be less and so on, causing you more handling problems then you even realize.

You're arguing against people who know and run these cars, some with great success, some of us even run the same tracks (BTW I have multiple top 3's at your track in only a few races and was track champion in cocopah last year), learn to take advice from people with success in this sport or you'll always struggle.

Let us help you get your gearing correct for your track and then we can help you set the car up properly. Oh, the car is built with the underslung bar where it is for strength on your particular chassis, so removing it and not replacing it somewhere else will severely weaken it.

[Confused?]

"Haven't been a lap down in years. Nice try though. "

You haven't been racing on dirt for years either. Read yourself another book about these cars. Seems to be working for you. Hopefully you may learn a little humility through this process. Only then will you be able to understand what's happening.

Enjoy your venture.....

[rob burgoon]

You haven't been racing on dirt for years either.

Wrong again. Y'all need to calm down.

Folks, if you're threatened by my asking questions and not blinding following suggestions, you should probably find another thread.

Your advice may be good, but if you say stuff that sounds like you don't know what you're talking about, I'm probably not going to follow it right away, no matter how long you've been racing.

If you can explain WHY a change would work, then I'm more inclined to take you seriously.

Rev limits and risk to engines have a potentially large impact on my budget, so I'm not likely to start taking chances there until I have the car handling well and need a torque boost.

Thanks to those that are contributing in good faith, but several of you guys need to take a deep breath and stop taking this thread so personally.

[rob burgoon]

I think it was past the end of IMCA season and those were "topless mod" non-IMCA races.

Yeah, in that video it was a lot of push then loose. Last few times it was more like "loose everywhere" in the dry. Most recently it was a little loose but kinda okish with decent tires on the back. If I had a test on friday and had to decide on changes right away, I'd probably add more bite, put new tires on the back, and see if I could mount the camera near the tach. Perhaps bring some old near bald tires to put on the back to check what wheelspin feels like.

[rob burgoon]

wow you got a weird way of trying to accomplish things that's for sure.

you can add air to the rear tires to feel wheel spin, lol.. It may take 10 psi or more on those tacky tracks if your still running that lugging gear

I just watched the under car video again. Are you guys thinking that the pulsing sound on the straights is lugging?

Most of the cars do that. Either its the rear pogo-ing or it's just bumps in the straight. You can hear it in last week's race vid.

https://www.youtube.com/watch?v=5k2C8C5IIdI&list=UU1-SpAdINV5H_iSmfNO8mzg

Rarrr-rarr-rarr down the straights.

[rob burgoon]

to watch you try and race, not so much...

You're safe, I wasn't in that race video. That race was shot from the stands by some guy that records all the races at barona.

[JustAddDirt]

good luck with your dirt experiment.
I have a feeling with the way you are going you will be going back to the Mazda on a road course pretty quick.
I don't care what you do either way, but when basically everyone here is telling you the same thing....change the gear, you might want to try changing it.
you can bet if I was a dirt guy going to a road course and struggling, I would be listening to as much information as possible from people that run well. Trial and error, there is no exact science to it
I will continue to watch this nice information session of a post, and see were it goes.

[rob burgoon]

good luck with your dirt experiment.
I have a feeling with the way you are going you will be going back to the Mazda on a road course pretty quick.
I don't care what you do either way, but when basically everyone here is telling you the same thing....change the gear, you might want to try changing it.
you can bet if I was a dirt guy going to a road course and struggling, I would be listening to as much information as possible from people that run well. Trial and error, there is no exact science to it
I will continue to watch this nice information session of a post, and see were it goes.

Listening, yes. Following all, no.

I believe the oldtrackchamp's suggestion about the bite was right on the money. I listened to that, liked the idea, followed it (partway), and the car got better. I will try increasing the bite further.

I also believe you guys are right about the 850 lb spring being too much. I couldn't feel the change, so I'm not shy about changing it back. I'll try that change in the second half of a test day at some point in the future, to avoid making too many changes at once.

I think you guys are right about the LR rail being too high, but that's a non trivial change. I need a pipe bender or to weld some sort of extensions to the tubes to make that happen. That, or just find a shop and write a check.

I don't think you guys are right about running a 6-6.2 rear end (at least at 5500rpm). I'm not going to drag the 6.2 gear across the garage, swap gears, pack up, drive to the track, try it, and drive back, risking the waste of a test day just because some guys on the internet say that running from 3-5k rpm will blow up my bottom end.

Much simpler to just log the tach and do the math.

Right now my car is getting better and I don't feel stuck, so I'm trying the stuff that sounds good first.

Gear changes will come later.

[Bcollins82]

The problem you are facing is that you need a setup "package" so to speak... you want to change one little thing at a time. You wont be happy with the results. And what works for one situation doesn't always work for another. Take for example your RF spring... changing it back to a 650 from an 850 right now won't help you. You have to have the "package" together with LR travel, spring rates, bar angles, weight distribution, frontend alignment and geometry, tires, and most importantly shocks. Because without the timing the correct shocks provide, its all for naught... You have people here trying to tell you FROM EXPERIENCE what works, and why. If you want to bury your head in the sand and pretend that your car is close, then that's completely up to you. But expect some backlash when someone that doesn't understand dirt cars starts asking questions without using the information being given. You can continue to try and run that car like that, but I can tell you that in 2010 I was determined I was going to make my cars fast without hiking up a ton. Just Add Dirt drove one of them... ask him how well it works... lol it seriously lacked drive and sidebite for the reasons I have given you already. I learned from my mistakes, and were all just here trying to help others that will listen. Good luck

[rob burgoon]

Asking questions should never generate backlash.

[Bcollins82]

Asking a question didn't create backlash.. arguing, disregarding the advice, and answering back with things like "you cant be serious?" probably will... lol And as far as what RRR is trying to sell you on, I hope it has a RF shock with insane low speed rebound numbers and a LR with tons of compression to help get it over on the RF and keep it there. Because with the low HP you are dealing with its already going to need help getting up and over. Thats why I put the 175 LR spring as an option, to help get the car to pop up easier. Im not saying what he's selling cant work, just that its not your "typical" chevelle clip 4 link mod spring combo. At least not in the last 10 years... The numbers I gave you arent "trick stuff" by any means. It's just a typical starting point for a chevelle clip 4 link car. If you want help further you'll have to post more info/pics...

[rob burgoon]

I see this as technical discussion. If anyone sees it as picking a fight, that's not what I'm after. I'm trying to learn the why, not just the what.

I honestly have NEVER heard of lugging ("jerk; hesitate; strain") happening in the powerband near the peak torque. I did some searches, haven't found mention of this as a thing to watch out for, except for cases of extremely wrong gearing. I asked someone smart and they suggested that there might be some kind of crazy resonance frequency thing going on with the rear axle able to rotate in these cars. I also checked video of the old alc engine running the 6.2 gear, and it pulsed down the straight too, just like most of the people I race against. Right now I honestly think the folks talking about lugging are either using lugging as hyperbole for "gearing somewhat too tall" or are trolling the new guy for giggles. Hence "you can't be serious".

But yeah, I appreciate help given in good faith, I'll post setup detail and pics later, the car is in the air right now, need to put wheels back on and get pics on the ground.

[RRR_Products]

Asking a question didn't create backlash.. arguing, disregarding the advice, and answering back with things like "you cant be serious?" probably will... lol And as far as what RRR is trying to sell you on, I hope it has a RF shock with insane low speed rebound numbers and a LR with tons of compression to help get it over on the RF and keep it there. Because with the low HP you are dealing with its already going to need help getting up and over. Thats why I put the 175 LR spring as an option, to help get the car to pop up easier. Im not saying what he's selling cant work, just that its not your "typical" chevelle clip 4 link mod spring combo. At least not in the last 10 years... The numbers I gave you arent "trick stuff" by any means. It's just a typical starting point for a chevelle clip 4 link car. If you want help further you'll have to post more info/pics...Then the cars running the fastest times at that track must be doing it wrong.

[Bcollins82]

Then the cars running the fastest times at that track must be doing it wrong.

Sounds like there's room for improvement...

[RRR_Products]

This track is usually tacky feature time unless the 4-6 feature and usually a cushion where the heavy rf works well. Last race a 550 lf and 750 rf against a 550 550/500 ran identical times feature time. Only when the track slicks off the lighter sprung car wasn't as free to the center from entry. Otherwise most have struggled in the tacky with lighter sprung front end and being consistent was an issue. It's more of a point and shoot track that diamonding is fastest unless it slicks off feature time and no cushion. But shock valving is a huge roll in this as well. Rob on a tacky track 16.5 is front runner time and dry black slick 17.5 you're walking away. If you want to get into every detail I have the corner/section times and speeds for the set ups that have worked at this particular track. You won't find many drivers going into this kind of detail like I think you're looking for. If you recall the asphalt data logging you've done I'm sure we can relate on this subject.

[charcoal01]

Nobody that I can tell suggested a 6.2 great ratio. That is in the ball park for an open. 5.43 or 5.67 would probably get you close.

Royce, I would hardly describe that track as a point and shoot. The corners are almost as long as the straights and there is no banking. Maintaining corner speed is the name of the game there.have you actually turned any laps there?

[RRR_Products]

Nobody that I can tell suggested a 6.2 great ratio. That is in the ball park for an open. 5.43 or 5.67 would probably get you close. Royce, I would hardly describe that track as a point and shoot. The corners are almost as long as the straights and there is no banking. Maintaining corner speed is the name of the game there.have you actually turned any laps there?That track is when tacked up very much a point and shoot tacky and bottom feeder when dry. Why do you think the heavy rf sprung cars are dominating when tacked up? I also do driver coaching and have to study a drivers habits and why a car is handling the way it is. Whether coaching road course, asphalt circle track or dirt it is all applied the same. I ran a full season at Barona In a street stock winning a championship and record amount of wins. Since I've tested in others cars and found out what's worked best since it is one of my local tracks. I am a firm believer In finding more speed always and always open to suggestions but I always have any driver strive for perfection and the speed comes naturally.

[Bcollins82]

RRR, nobody was telling him to get down to a 500 RF? My experience with tacky tracks is that you can run a softer spring and a lot of rebound in the RF, keep it pinned over, maybe a bit less LR drop, and the car is more consistent and easier to drive. Obviously you cant leave all the rebound in it when it slicks off, and you have to add drop back, or you'll lose some drive, but by that time the softer RF is usually better, even by your words... the problem I see most with tacky tracks, cushions, and softer RF setups is guys not wanting to limit their LR drop and that causes bad inconsistency on tacky/rough tracks. We set a track record (still stands) at 12.8 on a 1/4 mile track. It was tacky, and crazy rough. We had a 550 RF spring in the car (metric clip though) and applied some of the principles I mentioned here. We were well over 100hp down on some of the big guys, but the car was extremely consistent and drove great on the cushion. Sorry, no data loggers.... only trial and mostly error experience.... lol

[RRR_Products]

I agree BC82 there are so many set ups that work and don't work. I'm just sharing what has worked well at this particular track and I have found to be the most consistent. There isn't a magic set up but just from my experience seeing what's worked and hasn't worked I gave my input at this particular track.

[Bcollins82]

I agree BC82 there are so many set ups that work and don't work. I'm just sharing what has worked well at this particular track and I have found to be the most consistent. There isn't a magic set up but just from my experience seeing what's worked and hasn't worked I gave my input at this particular track.

More than one way to skin a cat... just happy to be talking chassis theory instead of gear ratios.... SMH... lmao!

[rob burgoon]

Nobody that I can tell suggested a 6.2 great ratio. That is in the ball park for an open. 5.43 or 5.67 would probably get you close.




probably needs to be a 6.00-6.20 rear end gear. (judging by videos)


JustAddDirt called for 6.0-6.2 and 6.2 is what's on my shelf.

[rob burgoon]

just happy to be talking chassis theory instead of gear ratios.... SMH... lmao!

That I agree with wholeheartedly.

[rob burgoon]

Do these links work for you guys?

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10417669_856734424345358_8166823757348273312_n.jpg ?oh=fb8a93ff02bde789189fed3f42cb74f7&oe=5486A2F1&__gda__=1417899309_b13671b470f2024f128f48cd378db48 2

https://scontent-b-sea.xx.fbcdn.net/hphotos-xpa1/v/t1.0-9/10646777_856734651012002_4935704227333077650_n.jpg ?oh=aff5eb0e7a8d1bf5d9b91879ee8833d4&oe=548851DD

https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10665206_856734937678640_4686451784472039031_n.jpg ?oh=aab4c699fde3091d2d01eb116578b2ff&oe=5486F4DB&__gda__=1422974471_de1cf6a748c70390377d1a908ff6d11 c

https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10665870_856735147678619_1716563646366871995_n.jpg ?oh=1438419420f0ff8b66ebcb20eb139226&oe=54A17DC4&__gda__=1419903256_e9fe56029505b1ff30e81f94d9b3915 7

https://scontent-a-sea.xx.fbcdn.net/hphotos-xfa1/v/t1.0-9/1654467_856735254345275_4597799877175141742_n.jpg? oh=cb50d1aac2375595f284b20c56fdfda6&oe=549228D0

https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-xaf1/v/t1.0-9/10703992_856735414345259_3186601890131763825_n.jpg ?oh=46ce3bdd723f6714f42223c8f871d927&oe=5485B61F&__gda__=1418715566_dc8c0c07d35f6d51f4e3ea9986bed56 8

[Bcollins82]

Do these links work for you guys?

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10417669_856734424345358_8166823757348273312_n.jpg ?oh=fb8a93ff02bde789189fed3f42cb74f7&oe=5486A2F1&__gda__=1417899309_b13671b470f2024f128f48cd378db48 2

https://scontent-b-sea.xx.fbcdn.net/hphotos-xpa1/v/t1.0-9/10646777_856734651012002_4935704227333077650_n.jpg ?oh=aff5eb0e7a8d1bf5d9b91879ee8833d4&oe=548851DD

https://fbcdn-sphotos-f-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10665206_856734937678640_4686451784472039031_n.jpg ?oh=aab4c699fde3091d2d01eb116578b2ff&oe=5486F4DB&__gda__=1422974471_de1cf6a748c70390377d1a908ff6d11 c

https://fbcdn-sphotos-d-a.akamaihd.net/hphotos-ak-xap1/v/t1.0-9/10665870_856735147678619_1716563646366871995_n.jpg ?oh=1438419420f0ff8b66ebcb20eb139226&oe=54A17DC4&__gda__=1419903256_e9fe56029505b1ff30e81f94d9b3915 7

https://scontent-a-sea.xx.fbcdn.net/hphotos-xfa1/v/t1.0-9/1654467_856735254345275_4597799877175141742_n.jpg? oh=cb50d1aac2375595f284b20c56fdfda6&oe=549228D0

https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-xaf1/v/t1.0-9/10703992_856735414345259_3186601890131763825_n.jpg ?oh=46ce3bdd723f6714f42223c8f871d927&oe=5485B61F&__gda__=1418715566_dc8c0c07d35f6d51f4e3ea9986bed56 8



Yeah, the links work fine. I'm not sure where to tell you to begin...

1. Ride heights are off by a mile. The RF is way too high. Reset them as I described, then re take pics up front.

2. It appears someone has added an underrail to the LR of your overrail car? From what I can see in the pictures, I believe you can just remove it...

3. On a spring behind 4bar LR your shock should be in front, with your spring in the rear on a slider or dummy shock. The way the birdcage indexes, you have very little control on the LR by having your shock behind.

4. Find someone that can rate your springs. I suspect the 850 you installed is giving up and that is why you couldn't tell a difference between it and a 650. Its old, and yellow. Those are 2 things you dont want to see with a spring. Buy quality springs when you purchase them. I prefer landrum, they don't seem to lose free height and come with a dyno sheet. But there are other good quality springs out there, like eibach.

5. You should be ready to fab LR upper shock mounts. Im not sure what kind of shaft will be showing after you reset ride heights, but what you have now looks to be too much even if you added an extension.

6. You should be a bit higher on left side and rear percentage IMO. 53.5 to 54 LS is what has worked well for me. You'll find people all over the place on rear, but you need to be at least 54 percent at a minimum. You just dont want to be bolting lead on farther back than the front of the fuel cell as a general rule. Getting rear percentage up by bolting weight on the back bumper will make your scale numbers look good, but the pendulum weight will make the car swing loose negating the effect.

7. Start talking to shock builders. Find one that is reputable, not a blowhard, and will help you with what you have instead of trying to sell you a new car. (Although, its not the worst idea at this point) I can't stress enough what the correct shocks will do to help a car IF everything else on it is correct. One piece that is bent or bound up and it doesn't matter what shocks are bolted on, you will struggle.

8. Adding a brake floater to the LR is pretty standard on this sort of setup. I would get with BSB and get one. Make the rod 2" longer than the LR upper.

9. Before you start, clean and grease everything, pull everything apart and be sure nothing is bound up, balljoints arent bent, heims are free, etc...

[save the racers]

two words.... CAR WASH

[Bcollins82]

two words.... CAR WASH


Haha! X2 on that... go to home depot and buy you some zep industrial degreaser and give it a thorough wash. Then repeat every time you go to the track.... just dont put it on decals full strength! There is a reason you rarely see a dirty car go fast....

[rob burgoon]

3. On a spring behind 4bar LR your shock should be in front, with your spring in the rear on a slider or dummy shock. The way the birdcage indexes, you have very little control on the LR by having your shock behind.


Are dummy shocks legal in IMCA mods?

"One steel, nonadjustable, unaltered shock per wheel. All shocks must completely collapse at any time. One additional shock allowed
in pull-bar area. No external or internal bumpers or stops. No threaded body, front coil-over, air, or remote reservoir shocks. No Schrader or
bladder type valve allowed. Front half may be shielded. One or all shocks may be claimed per event for $50 each, counting as one claim on card,
following shock claim procedures (Refer to www.imca.com)."

[Bcollins82]

Are dummy shocks legal in IMCA mods?

"One steel, nonadjustable, unaltered shock per wheel. All shocks must completely collapse at any time. One additional shock allowed
in pull-bar area. No external or internal bumpers or stops. No threaded body, front coil-over, air, or remote reservoir shocks. No Schrader or
bladder type valve allowed. Front half may be shielded. One or all shocks may be claimed per event for $50 each, counting as one claim on card,
following shock claim procedures (Refer to www.imca.com)."

Evidently not. Have to get a good quality slider. The cheap ones will bind up.

[JustAddDirt]

BSB coil over eliminator (or slider) is what you need.
put coil on rear with the new BSB part
put shock on front of birdcage to control the compression and rebound of LR suspension.

Found another reason you say you are spinning, and no traction. By your photos of rear of car on scales
your rear tires are bald. lol
this is not pavment roundy round, it is dirt, need tread on tires. I also recall reading on one of your other posts that you quit testing because rear tires were cording. If you are running them that long, that they are showing cords, that is way too long. Rear tires should be new every couple races to be competitive. The G 60 tires you are running should last a good bit of runtime, but that is a extreme.

[rob burgoon]

Found another reason you say you are spinning, and no traction. By your photos of rear of car on scales
your rear tires are bald. lol

Well yeah, I mentioned that in the report after the test day. Dying tires explain mid-day changes toward oversteer. The handling issues were still happening with new rears before the more recent changes.

Test in two days. New rears going on, I'll drop the right side another inch to get it vaguely level, and check the front cross member height. If I have time I'll move the 30lbs of lead from the RR to the LR. (grr... it's welded in). Might add fuel or delete the extinguisher bottle or front bumper temporarily to get more weight aft.

In the meantime I'll start ordering rear suspension parts for some of the other changes.

[Bcollins82]

Listen, I know you need seat time. But as I explained before, you need a total package change. Changing one or two little things at a time like the stuff you are mentioning won't do a lot by themselves. You really need to consider holding off until you can get the car together correctly. You need to devote some serious shop time and attention to do an update on your complete setup and go through everything thoroughly to clean, lube, check for bent or binding parts, make sure you don't have any dead springs, etc... You'll just be burning tires and fuel for the fun of it if not... and why start moving weight when you are that far under minimum already? Just bolt some on.. Does your track not have scales?

[Bcollins82]

If you just want to go play, buy some used tires from the fast guys. You can usually pick them up for next to nothing. No sense in burning up new ones when the car is that far off. But hey, not my money... lol

[rob burgoon]

and why start moving weight when you are that far under minimum already? Just bolt some on.. Does your track not have scales?

That weight is without driver.

[Bcollins82]

That weight is without driver.

Ah.. scale with driver or at least simulated driver weight. I know some people like to scale without, but I don't agree... You don't race without a driver, so why scale that way? It throws off percentages and ride heights both. So your ride heights are even farther off than I previously thought... Sit down in it and record the real numbers and let us know, then you can go from there.

[rob burgoon]

Ah.. scale with driver or at least simulated driver weight. I know some people like to scale without, but I don't agree... You don't race without a driver, so why scale that way? It throws off percentages and ride heights both. So your ride heights are even farther off than I previously thought... Sit down in it and record the real numbers and let us know, then you can go from there.

Yeah, in sports car land it's always with driver, but I kept coming across dirt setup stuff that listed numbers without driver, so figured that was a cultural thing. Glad to hear it's not too widespread, haha.

[Bcollins82]

Yeah, in sports car land it's always with driver, but I kept coming across dirt setup stuff that listed numbers without driver, so figured that was a cultural thing. Glad to hear it's not too widespread, haha.

Yeah, I've never understood why someone would scale a car like that. You can always spot them at the track because the LR is tucked up in the wheelwell and the RF is up in the air... It sure doesn't make things very repeatable.

[mod88s]

Ive raced on dirt for over 25 years and have always scaled without driver. I started doing it this way because that is how the manufacturer said I should do it. I would say the vast majority of dirt trackers do it the same way. There have been a couple of manufacturers lately(GRT) who say to scale with driver or simulated driver weight in car. It is up to the manufacturer and how the car was designed. Remember why you scale your car, to get to a good base set up. Then you tune from there. Also scale because it can identify problems elsewhere in the car. Or incase you damage the car you can get it back to the base set up. Absolutely no problem scaling without driver or driver weight.

[Bcollins82]

Ive raced on dirt for over 25 years and have always scaled without driver. I started doing it this way because that is how the manufacturer said I should do it. I would say the vast majority of dirt trackers do it the same way. There have been a couple of manufacturers lately(GRT) who say to scale with driver or simulated driver weight in car. It is up to the manufacturer and how the car was designed. Remember why you scale your car, to get to a good base set up. Then you tune from there. Also scale because it can identify problems elsewhere in the car. Or incase you damage the car you can get it back to the base set up. Absolutely no problem scaling without driver or driver weight.

Scale your car with a 225 LR spring, sit in it and measure ride heights, wheel weights, etc.. then do the same with a 175 LR scaled the same without the driver. When you put the driver in the car the ride heights, wheel weights, and bar angles will be different when you hit the track with different spring rates.... I realize some chassis builders tell you to do it like that, but its not the most consistent, repeatable way to do so. You are correct, it's just a baseline, but I want the most consistent baseline possible. So in my book, there is a problem scaling without the driver. Just my opinion...

[rob burgoon]

If I wanted to scale without driver and I was willing to cut some corners, I would scale once with & without driver, and measure how big the difference was (weights, ride heights, bar angles). Write down these differences and now you have a way to guess at what the car would be like with driver. For example, if the LR sags about half an inch and you gain 1% left and 1% rear, now you know to set your car up without driver to have the LR half an inch too high.

Not terribly precise, but helpers aren't always around.

But yeah, sand bags or a patient human with a book in the driver seat is probably best for setup.

[ask0329]

Rob, I feel at times i was in the same situation as you and here is what i've done. My car is a 4-link imca mod. We always run on dry slick. I too ran a 602 although I did not have to. My track was 1/3 mile moderately banked D. I ran 5:29 gears and would hit the rev chip at 6200 on occassion. Not too often but every now and then. Why? Cause my overall setup was bad, I was spinning the tires and in expierenced. I really think you would be fine going to atleast 5:29 gears and a 6200 chip. As for setup, I was out to lunch pretty much every race. Its taken me close to 4 years to get the car dialed in mostly cause it was home built and I was knew. Finally a fella started helping me who was the only other guy that ran a metric clip, with metric lowers and metric spindles. The last few races have been night and day and the car is a million times better. I too had an underslung car and was hitting it. I cut that right out of there probably 2 years ago now. We just put an additional bracing bar from the tail section up. As for setup, what these guys are saying is right on the mark. Ride heights slightly higher on the left than right. if you have a chevelle clip 850 is way too high. Thats a spring for a metric clip with metric lower. The differnet clips and lowers have different motion ratios due to their length. One last thing, when the new fella started coming over to my garage and wanted to make all these changes that i just thought where bizaar I was really put off by it. The more I got to thinking I said to myself, we have 3 races left, I'm not racing for points. What do i have to lose? So we threw every change at it he told me to do and my god, I'm so happy i did.

[mod88s]

Scaling without the driver is just as consistent as scaling with driver. The only difference is the driver is not in the car on the scales. Whether you scale with or without driver, you set the numbers to where you want them on the scales, then you go race the car. You make changes to the car based on what the car tells you on the track. Whether the driver was in the car or not during scaling wouldn't make any difference in the world on your thought process about what to changes to make. If the car was loose on entry, you need to tighten it up. If it was too tight on entry, you would make changes to loosen it up. How you scaled the car makes absolutely no difference, as long as you do it the same way every time.

[Bcollins82]

Scaling without the driver is just as consistent as scaling with driver. The only difference is the driver is not in the car on the scales. Whether you scale with or without driver, you set the numbers to where you want them on the scales, then you go race the car. You make changes to the car based on what the car tells you on the track. Whether the driver was in the car or not during scaling wouldn't make any difference in the world on your thought process about what to changes to make. If the car was loose on entry, you need to tighten it up. If it was too tight on entry, you would make changes to loosen it up. How you scaled the car makes absolutely no difference, as long as you do it the same way every time.

I understand your theory, and there have been a lot of races won that way. But I just explained in detail why it is not as consistent to scale without driver weight. Its not just theory, you actually pull on the race track with different ride heights and wheel weights if you scale without the driver and change spring rates. I don't want to go through figuring out what my ride heights will be with different springs so the bar angles and wheel weights are the same after a spring change. I find it much easier to just have the weight in there to begin with. There is a reason all of the major late model manufacturers scale with driver weight.
It seems like it is a lot more common to scale without the driver out in imca land so I haven't ever dealt with a builder that recommend scaling without driver weight. I'm curious, do they give you different percentages and ride heights for different driver weights? I mean, if you scale without driver and one guy weighs 150 and the next guy is 250 that's a huge difference in wheel weight and ride heights... It seems like that would make it harder to share info between drivers of different sizes as a builder. Maybe I'm just worried too much about getting the heights and weights exact...

[mod88s]

Ive raced all over the country including nascar modifieds, and won some races here and there so I have experience outside of IMCA land as you put it. I have heard very few manufacturers recommend scaling with driver or driver weight. It should take you about 2 races to figure out what springs to run in your car so Im not sure why you are so concerned with ride heights and bar angles after changing springs. You make it sound like you are changing springs all the time which I don't understand why you would have to do that. Once in a while I might make a RF spring change at the track depending on track conditions. But its not rocket science to get it back to the same ride height and wheel weights. I guess keep on keepin on if you want to go through the hassle of simulating driver weight. If it keeps your mind at ease and you feel its the magic ticket, keep on doing it.

[Bcollins82]

Ive raced all over the country including nascar modifieds, and won some races here and there so I have experience outside of IMCA land as you put it. I have heard very few manufacturers recommend scaling with driver or driver weight. It should take you about 2 races to figure out what springs to run in your car so Im not sure why you are so concerned with ride heights and bar angles after changing springs. You make it sound like you are changing springs all the time which I don't understand why you would have to do that. Once in a while I might make a RF spring change at the track depending on track conditions. But its not rocket science to get it back to the same ride height and wheel weights. I guess keep on keepin on if you want to go through the hassle of simulating driver weight. If it keeps your mind at ease and you feel its the magic ticket, keep on doing it.

I've been around a while too, but I have never been one to sit back and leave things alone. So yes, changing springs has been a common thing. It does keep my mind at ease knowing that from spring to spring, driver to driver, car to car, when the car rolls on the track you have an apples to apples comparison between them. No, its not rocket science to get it back to ride height after a spring change. My point is that if you have 2 different springs at the same static height and the same wheel weights without the driver, they will be different after you put driver weight in the car. Not to mention every driver in brand X not weighing the same. I don't think its rocket science to grasp that concept either... I have never accepted "we've done it that way for years" as an answer to any question. Even if doing it that way has been successful, I look at it as there's always room for improvement. I can tell you that people like Cj Rayburn, Keith and Tader Masters, and Mark Richards want their cars scaled with driver weight for a reason. The 4bar spring behind LR suspension is designed to make the LR spring act softer through birdcage rotation so the effects are magnified when you add driver weight. They are also sensitive to bar angles and wheel weights. So yes, I will keep on keepin on. I can even explain why without just throwing experience out there as my reason.

[mod88s]

I understand your point about having 2 different springs without driver that they will be different after you put driver weight in the car, I really do. Its a very simple concept to grasp. Im not arguing that. But you are completely missing my point that it is 100% irrelevant in setting up a race car. Whether you scale a car with driver or without REALLY doesn't matter, as long as you do it the SAME WAY, EVERYTIME. And listen to your builder. That's MY point. If you have a decent builder, they have already taken these things into consideration. For example, Most times they give a range like 52.2-52.5% left side weight. If you are a heavy fella, you would scale to the lower end of the scale and vice versa. I can start name dropping like you did and give you a list of 100 people and 10 different brand name chassis that do not scale with driver weight and tell you they do it for a reason too but whats the point. Just helps me prove my point, some people scale with driver, some don't.. REALLY doesn't matter. As far as stating your theory about what the 4bar spring behind is designed to do, that's a whole other can of worms.

[Bcollins82]

I understand your point about having 2 different springs without driver that they will be different after you put driver weight in the car, I really do. Its a very simple concept to grasp. Im not arguing that. But you are completely missing my point that it is 100% irrelevant in setting up a race car. Whether you scale a car with driver or without REALLY doesn't matter, as long as you do it the SAME WAY, EVERYTIME. And listen to your builder. That's MY point. If you have a decent builder, they have already taken these things into consideration. For example, Most times they give a range like 52.2-52.5% left side weight. If you are a heavy fella, you would scale to the lower end of the scale and vice versa. I can start name dropping like you did and give you a list of 100 people and 10 different brand name chassis that do not scale with driver weight and tell you they do it for a reason too but whats the point. Just helps me prove my point, some people scale with driver, some don't.. REALLY doesn't matter. As far as stating your theory about what the 4bar spring behind is designed to do, that's a whole other can of worms.

Lol so I guess that means you don't agree with my 4 bar theory either? Thats cool... I tend to look at things differently than most. And yes, I completely understand and agree with you that if you scale the same way, same car, same driver, same springs, you can be consistent scaling without a driver. But just saying if you are a big fella, you run the low side of the recommended percentages is just a shot in the dark to get you in the ballpark where you can tune from there. And that's why I will never understand why any builder can recommend scaling like that. They would have to have a ride height chart for different driver weights to keep a consistent ride height from car to car.... I can go to the track with car A, find something better, call guy with car B in another state that is 100lbs heavier and he can set his car exactly to the pound the same, with ride heights dead on, and we can share factual information and remove as many variables as possible. That is a reality that I have to deal with every week. It is consistent and it is repeatable. If you can explain to me how you do that without a driver in the car I'll owe you a handshake and a tylenol from doing the math to figure it out. Lmao

[mod88s]

Get your shakin hand warmed up because I do the same thing every week. I talk to many of my buddies week to week bouncing new setups and ideas off of each other. For example, if I tried something and it helped my car to turn better through the middle of the turns, I could tell my buddy what changes to make and guess what?? It helps his car turn better through the middle as well! We don't have to weigh the same, or have the EXACT same ride heights, or have the EXACT same wheel weights, or have the EXACT same bar angles. The general effects are the same no matter what brand of car you are in. If I tell a guy to raise his right side lower bar to 10 degress from 5 degrees, I know it is going to loosen up his entry. Im sure thousands of racers around the country chat with all their racing buddies and share info, do you think they have the exact same ride heights/bar angles/wheel weights? So it really is comparing apples to apples. The reason car builders tell you to do things a certain way IS BECAUSE THEY HAVE EXPERIENCE AND KNOW WHAT THEY ARE DOING. At least most of the reputable ones anyway.

[Bcollins82]

Get your shakin hand warmed up because I do the same thing every week. I talk to many of my buddies week to week bouncing new setups and ideas off of each other. For example, if I tried something and it helped my car to turn better through the middle of the turns, I could tell my buddy what changes to make and guess what?? It helps his car turn better through the middle as well! We don't have to weigh the same, or have the EXACT same ride heights, or have the EXACT same wheel weights, or have the EXACT same bar angles. The general effects are the same no matter what brand of car you are in. If I tell a guy to raise his right side lower bar to 10 degress from 5 degrees, I know it is going to loosen up his entry. Im sure thousands of racers around the country chat with all their racing buddies and share info, do you think they have the exact same ride heights/bar angles/wheel weights? So it really is comparing apples to apples. The reason car builders tell you to do things a certain way IS BECAUSE THEY HAVE EXPERIENCE AND KNOW WHAT THEY ARE DOING. At least most of the reputable ones anyway.

Why is this concept so hard to grasp? Yes, adjustments work the same from car to car for the most part. But we aren't talking adjustments, were talking about what gets everyone on the most accurate and consistent baseline to have a good starting point to make adjustments from. If your buddies car is identical, but he starts off higher on LS percentage, has more wedge, more rear percentage, and less LR bar angle with him in the car because he's bigger than you, the same springs, shocks, and bar angles won't start his car off balanced like yours, it will take adjustments from where you began (even though your numbers were identical on the scale) to get his car working like yours when he could've avoided the tuning session and just started there to begin with by scaling with the drivers weight in the car... It's very simple. Track time is expensive, scale time isn't... And you still haven't explained to me how you get on an even starting point car to car without driver weight... that IS what we're talking about as we hijack Robs thread, right? Lol

[mod88s]

I have explained it several times, go back and read my posts. You are just too stubborn to see it. Im gonna say it one last time. No matter if you have driver weight in car or not, you go by what the manufacturer tells you to for a starting point/baseline setup and tune from there. If they tell you scale with driver in car, then do it that way. If they say no driver, 15 gallons of fuel, then do it that way. THAT IS YOUR BASELINE SET UP, TUNE FROM THERE. Its that simple. Give your car what it needs after that. Period. End of story. Just because a guy is a little heavier or a little lighter than you DOES NOT MATTER, IT DOES NOT MATTER, because the concept you are missing here is that ITS JUST A BASIC STARTING POINT AND YOU TUNE FROM THERE. The manufacturer gets you in the ballpark, the rest is up to you. I get your point that "what if the other guys weighs more than you, then you wont have the same ride heights/bar angles etc..." but the point you are missing is that IT DOESNT MATTER. IT DOESNT MATTER. EACH DRIVER HAS A DIFFERENT DRIVING STYLE, RACE ON DIFFERENT TRACKS ETC... You get a starting point, and go from there.

[Bcollins82]

Lmao Listen, you can get mad an TYPE IN CAPITALS all you want, but you've never explained why doing it your way is more consistent. That's because it isn't. I can explain why driver weight is more consistent, and give examples, but no matter how many times I explain it, and explain why, you will refuse to see it that way because that is how you've always done it. I'm not being stubborn, I have valid fact based points. Your argument is a chassis builder is there to get it halfway close, consistent ride heights and wheel weights as you roll on the track mean nothing, and let you figure it out from there... lol Of course you'll have to tune and adjust to track condition and driving style, why add having to tune from starting off base from the other guys that run the same cars? That's absurd. There's a better way for any chassis builder to start everyone from a more consistent platform to make information sharing more effective. Period.

[mod88s]

Not once have I said scaling without driver was MORE consistent. However I believe that it is just as consistent as scaling With driver. And Im definitely not mad, I was just trying a different affect to help you see my point, but it didn't work. I should have listened to stock car driver, you are still trying to get your point across about driver weight affecting ride heights/bar angles which I have ALREADY AGREED WITH YOU on, but for some reason keep trying to get that point across. You cant seem to move off that point and look at what Im trying to explain to you. You can twist and distort what Im trying to say to you but the fact remains that more races have been won by scaling cars without driver, and that's a fact. Im enough of a man to stop arguing at this point and I will just agree to disagree on your basic premise that scaling a car with a driver is better than scaling without. And my point remains, one way is not necessarily better than the other.

[Bcollins82]

Cute couple ^^^

Hahaha! Oh yeah, that dude loves me. Sorry to Rob Burgoon for the thread hijack, I've made my point, I'm done.

[rob burgoon]

Rob, I feel at times i was in the same situation as you and here is what i've done. My car is a 4-link imca mod. We always run on dry slick. I too ran a 602 although I did not have to. My track was 1/3 mile moderately banked D. I ran 5:29 gears and would hit the rev chip at 6200 on occassion. Not too often but every now and then. Why? Cause my overall setup was bad, I was spinning the tires and in expierenced. I really think you would be fine going to atleast 5:29 gears and a 6200 chip. As for setup, I was out to lunch pretty much every race. Its taken me close to 4 years to get the car dialed in mostly cause it was home built and I was knew. Finally a fella started helping me who was the only other guy that ran a metric clip, with metric lowers and metric spindles. The last few races have been night and day and the car is a million times better. I too had an underslung car and was hitting it. I cut that right out of there probably 2 years ago now. We just put an additional bracing bar from the tail section up. As for setup, what these guys are saying is right on the mark. Ride heights slightly higher on the left than right. if you have a chevelle clip 850 is way too high. Thats a spring for a metric clip with metric lower. The differnet clips and lowers have different motion ratios due to their length. One last thing, when the new fella started coming over to my garage and wanted to make all these changes that i just thought where bizaar I was really put off by it. The more I got to thinking I said to myself, we have 3 races left, I'm not racing for points. What do i have to lose? So we threw every change at it he told me to do and my god, I'm so happy i did.

Thanks ask! Yeah, I coming to believe the 602 can do 6200, I'll switch the gearing for that at some point. On this last practice I discovered that there are some bumps at the end of the back straight, and also if the rear grip is kinda bad, the rear tires can spin in something like a controlled fashion and have the tach steadily climbing, but reading 1,000 high compared what the ground speed should be.

I think you are right, a modest shortening of gear and rev limit extension together is probably the ticket.

The 850 spring went on just as a experiment to answer 1: what happens if I try the old factory setup? and 2: can I make this thing push?

[rob burgoon]

Hahaha! Oh yeah, that dude loves me. Sorry to Rob Burgoon for the thread hijack, I've made my point, I'm done.

No worries.



Did a test on friday, I some of the parts I ordered haven't arrived yet and temps have been near 100 lately, so not much happened in the garage since you gave me the list of suggestions. I have some schedule conflicts coming up so wanted to get out there. Had fresh rears on hand as spares, but ended up using up the old inventory AND I believe I managed to learn something on the dying rears.

DISCLAIMER: What follows are my theories, they may or may not be correct.

Even though the droop chain isn't in place yet, your suggestions got me thinking about the role that a limiter plays in on throttle handling. Specifically, what happens when you run out of LR travel. When that happens, any additional attempt by the axle to apply force vertically attempts to stretch the chain instead of lifting the car. I suspect this means that as you raise the LR upper bar, you will reach a point where raising it further won't seem to tighten it much more. It might lift the back of the car faster, but once it gets there, there's no additional bite for the LR to tighten the car.

Since I wasn't able to lengthen the travel before the test, I figured I'd do the next best thing, drop the RR upper a hole and decrease the load on the RR as well as decreasing the roll steer.

Even on rear tires that were starting to look thin, the ability to mash the gas and have the car go straight-ish was noticeably improved. The car was much more drivable in the black slick on exit. I suspect that extending the chain without the change to the RR upper would have been similarly effective.

As I mentioned in the previous post, I was feeling carefully for wheelspin this time and was noticing subtle wheel spin as the rears wore, eventually getting to the point where they would zing, but before that, slipping in a sneaky fashion. A somewhat shorter gear is in my future.

Sessions 1 and 2 were dry and a mix of brown and black, featured improved handling at full throttle, and periodically a death push would occur off throttle or slight throttle (probably the 850 spring and RF height). During this session to avoid the push by keeping the rear up I started getting fond of putting weight on the nose under braking, shifting the weight over from the nose to the right side in a smooth motion. I think I'm starting to see what you're getting at about having the RF softer and the car leaned to the right slightly when sitting still.

At this point I dropped the RF ride height an inch, to get closer to your suggested ride heights and see what would happen. The session 3 the rears started spinning on exit due to loss of tread on the LR, and the offthrottle push had gotten milder.

I wanted to ditch the 850 spring, but didn't have time so I figured I'd retest the last change with less-dead tires.

Sessions 4 and 5 felt that the off throttle push was indeed reduced, but it's difficult to be certain since I was still rotating lots on entry.




Conclusions:
Your suggestions seem good. I should try more of them.


My setup theories:
Trying to change on throttle handling with RF spring isn't that effective.
Trying to change on throttle handling with cross/bite isn't that effective.
Trying to get a push by raising LR upper stops working at a certain point.
Change the rear bars to make on throttle behavior changes.
Rear bars settings tune "dynamic bite" between the rear tires under power.
Rear ride height and springs *might* not matter much (indexing could play a role with LR spring, don't understand it yet)
Handling can be split into at least two states: on throttle, off throttle. On uses bars and a subset of the springs, off uses cross weights and all springs. My on throttle handling is ok, I need to fix the off. Going back to softer RF spring will probably help.

Known unknowns:
What the heck does a floating LR brake do? The physics makes my head hurt. I need to draw a picture or something to try to understand it.

"That's racing":
This morning I learned that at the current ride height, when backing off the trailer the oil pan will catch the trailer bringing the car to an abrupt halt. F&*#!

[rob burgoon]

Videos available upon request. If anyone is curious to see a particular session, I'll upload it.

[Bcollins82]

No worries.



Did a test on friday, I some of the parts I ordered haven't arrived yet and temps have been near 100 lately, so not much happened in the garage since you gave me the list of suggestions. I have some schedule conflicts coming up so wanted to get out there. Had fresh rears on hand as spares, but ended up using up the old inventory AND I believe I managed to learn something on the dying rears.

DISCLAIMER: What follows are my theories, they may or may not be correct.

Even though the droop chain isn't in place yet, your suggestions got me thinking about the role that a limiter plays in on throttle handling. Specifically, what happens when you run out of LR travel. When that happens, any additional attempt by the axle to apply force vertically attempts to stretch the chain instead of lifting the car. I suspect this means that as you raise the LR upper bar, you will reach a point where raising it further won't seem to tighten it much more. It might lift the back of the car faster, but once it gets there, there's no additional bite for the LR to tighten the car.

Since I wasn't able to lengthen the travel before the test, I figured I'd do the next best thing, drop the RR upper a hole and decrease the load on the RR as well as decreasing the roll steer.

Even on rear tires that were starting to look thin, the ability to mash the gas and have the car go straight-ish was noticeably improved. The car was much more drivable in the black slick on exit. I suspect that extending the chain without the change to the RR upper would have been similarly effective.

As I mentioned in the previous post, I was feeling carefully for wheelspin this time and was noticing subtle wheel spin as the rears wore, eventually getting to the point where they would zing, but before that, slipping in a sneaky fashion. A somewhat shorter gear is in my future.

Sessions 1 and 2 were dry and a mix of brown and black, featured improved handling at full throttle, and periodically a death push would occur off throttle or slight throttle (probably the 850 spring and RF height). During this session to avoid the push by keeping the rear up I started getting fond of putting weight on the nose under braking, shifting the weight over from the nose to the right side in a smooth motion. I think I'm starting to see what you're getting at about having the RF softer and the car leaned to the right slightly when sitting still.

At this point I dropped the RF ride height an inch, to get closer to your suggested ride heights and see what would happen. The session 3 the rears started spinning on exit due to loss of tread on the LR, and the offthrottle push had gotten milder.

I wanted to ditch the 850 spring, but didn't have time so I figured I'd retest the last change with less-dead tires.

Sessions 4 and 5 felt that the off throttle push was indeed reduced, but it's difficult to be certain since I was still rotating lots on entry.




Conclusions:
Your suggestions seem good. I should try more of them.


My setup theories:
Trying to change on throttle handling with RF spring isn't that effective.
Trying to change on throttle handling with cross/bite isn't that effective.
Trying to get a push by raising LR upper stops working at a certain point.
Change the rear bars to make on throttle behavior changes.
Rear bars settings tune "dynamic bite" between the rear tires under power.
Rear ride height and springs *might* not matter much (indexing could play a role with LR spring, don't understand it yet)
Handling can be split into at least two states: on throttle, off throttle. On uses bars and a subset of the springs, off uses cross weights and all springs. My on throttle handling is ok, I need to fix the off. Going back to softer RF spring will probably help.

Known unknowns:
What the heck does a floating LR brake do? The physics makes my head hurt. I need to draw a picture or something to try to understand it.

"That's racing":
This morning I learned that at the current ride height, when backing off the trailer the oil pan will catch the trailer bringing the car to an abrupt halt. F&*#!

1. You are correct on LR upper angle. That is why most people suggest 45 degrees of angle at maximum droop. After that seems to be the point of diminishing return.

2. Lowering the RR upper will do exactly what you were thinking. Try to keep vertical separation at the chassis around 14 to 14.5" that's just a starting point, but farther apart causes the RR to feel stiffer, closer together and the RR feels softer.

3. I disagree with the RF spring not being an effective way of changing on throttle handling. It plays a large role because that is what the LR is shoving against as it picks up and transfers weight, so it affects chassis attitude, and how easily the LR is able to get up. So it definitely is an effective way to tune. That's why it's usually the first question most racers will ask each other.

4. Changing on throttle handling with cross is effective. A small change in static cross weight isn't as dramatic as changing bar angles. Once you get everything closer, its a very effective way of tuning.

5. Rear ride height and springs are very important. I feel the LR spring on a 4bar spring behind is really only used as a tool to get the LR up more quickly/easily (softer) if you need it. The RR spring is very important, as it tunes entry by making it tighter as you stiffen it, it has a large influence on side bite, and exit because the rate of the spring can change RR drive/loading not only straight through the spring, but it can also change the RR thrust angle because of dynamic ride height changes. You learned in your test that changing the RR bar angles can make a drastic change in handling, and ride height goes hand in hand with those angles. That is why they are so important to keep consistent.

6. A LR floater applies force to the chassis through braking energy, keeping weight over on the RF, and keeping the LR from settling as far on entry braking.

[rob burgoon]

6. A LR floater applies force to the chassis through braking energy, keeping weight over on the RF, and keeping the LR from settling as far on entry braking.

Drew the picture. This checks out. Sitting outside of the LR tire looking at the tire and brake with the brake fixed to the axle, the tire rotates CCW, the brake exerts force CW, the reaction on the brake caliper mounts (the axle) is twisted CCW.

With a brake floater, the reaction force on the floater is still CCW, if you attach it on top using an upward inclined rod, wham-bam you're now attempting to lift the rear end using the brake pedal. Clever.

[Bcollins82]

Run a bar 2" longer than your upper 4 link bar, and run it parallel to your upper 4 link bar. The floater rod has a lot of force on it so they can over center or "cam over" the longer rod elimates that trouble.

[rob burgoon]

1. You are correct on LR upper angle. That is why most people suggest 45 degrees of angle at maximum droop. After that seems to be the point of diminishing return.


I don't think 45 is the limit I'm running into. Once you use up your travel, *clang* the axle smacks into the limiter (undertube in my case). Once this happens, changing the static angle on the LR bar to be steeper won't change much. When the clang happens, the angle on the bar could be 30, 35, 45, but none of those should be very different other than how fast the rear of the car came up.

Adding more droop travel should allow the clang to occur later and for more dynamic LR bite from the "vertical force".

[Bcollins82]

I don't think 45 is the limit I'm running into. Once you use up your travel, *clang* the axle smacks into the limiter (undertube in my case). Once this happens, changing the static angle on the LR bar to be steeper won't change much. When the clang happens, the angle on the bar could be 30, 35, 45, but none of those should be very different other than how fast the rear of the car came up.

Adding more droop travel should allow the clang to occur later and for more dynamic LR bite from the "vertical force".

That's correct. No more dynamic loading if its against a travel stop and staying there no matter what spring, shock, or bar angle you have in the LR. You effectively make the LR solid on throttle. Watch your LR in the under car video you posted before. The LR stays pretty much solid on throttle. The RR is the only one moving as you are on throttle. That is why LR drop is a very critical and effective adjustment on these cars.

[Toywagon]

I want to throw out something, even tho it is slightly bringing up the gear ratio topic again......

I run on mostly flat and medium banked 1/4 bullrings. Almost all of them go to dry slick, or even dusty slick at times.

I do not gear for maximum power/rpm/mph at the end of the straightaway on these bullrings. IMO having the most mph or track speed at corner entry isn't as much of an advantage as being able to drive from mid corner and off with a bit deeper gear as well as being in a better rpm range etc.

I do not like changing gears on a 9 inch either. During hotlaps, and if we manage to get a tacky track for heat races, I just lift up off the throttle slightly as I near the end of the straight away if I run up on the chip. I don't lift much, just enough to let the engine stop climbing or just banging on the chip.

IMO on these bullrings, it just works better for me to get from the middle of the corner to mid straightaway better than the other guys. Maybe something for you to try when you put the 6.20 in and it gets on the chip too soon.

Jim

[rob burgoon]

Thanks Jim, I'll make the change in the offseason.

The season is done, for the last test day I played around with more rear steer and that seemed to make the car more controllable while sliding midcorner. Entered the last race of the season, race was fun, but the car got way too pushy on entry. I let the RF tire get too worn and that killed the car's ability to rotate I think. The track ended up semi-tacky. I'm bummed I didn't run a better RF tire since I think the setup was close to being somewhat viable.

More recently I made a model of the 4 bar suspension using pined paper and learned how the thing moves with different angles. Interesting stuff. I had no idea how much indexing increases when you point the lower bar lower to reduce rear steer.

[JustAddDirt]

Ron,
Looks like you have learned quite a bit from your test sessions.

[rob burgoon]

Getting there. One thing my dad picked out from a video is that my car's rear squirts out on throttle application more than anyone else's in the field, despite my short gearing and weak engine, even on fresh tires.

I was watching some videos of other mods on tracks elsewhere in the country and saw that out of the entire field, not a single car's RR moved appreciably within the wheel well. Comparing to my rear axle video, my car gets up on its RR noticeably.

For the next event I'm going to reduce the angle of the RR upper bar to reduce downforce and steer on the RR. My suspicion is that the balance between LR and RR is wrong when I get on the gas.

[rob burgoon]

6.2 is in the car, rev limiter raised to 6,200, removed a spacer from the RF just for fun. Was on 3 new tires and a used LF in very good shape. 0 stagger unfortunately, a tire wasn't holding air and had to change it last minute.

Engine didn't blow up. Seems like I'm on the limiter for most of the straight, but I think that's mostly wheelspin.

Includes warmup, race begins at 9:45
https://youtu.be/2FiC1SRAqIk

Seems like the LR comes up at 15% throttle, I *think* the RR comes up at 60-70% throttle. Gonna screw around with spacers and some stagger next time.

I suspect I'm tight on entry and mid.

[stock car driver]

I watched first few laps of your video, looks like too much gear to me now.

fyi when your on the chip like that your not gaining speed anymore so don't be scared to stay wide open and drive thru the corner. when the track is like the one you were on you should easily be able to flat foot it all the way around, theres plenty of cushion, moist dirt to help you turn. you were staying in the middle off the good of the track.

You could go in low like you were wide open and slide up to the cushion and arch the corner or just go in higher like the cars in front of you on the restart and arch the whole thing around.

Id only cut down to the bottom on a track like that if my gear was limiting me or I was passing cars.

[JustAddDirt]

Getting there. One thing my dad picked out from a video is that my car's rear squirts out on throttle application more than anyone else's in the field, despite my short gearing and weak engine, even on fresh tires.

I was watching some videos of other mods on tracks elsewhere in the country and saw that out of the entire field, not a single car's RR moved appreciably within the wheel well. Comparing to my rear axle video, my car gets up on its RR noticeably.

For the next event I'm going to reduce the angle of the RR upper bar to reduce downforce and steer on the RR. My suspicion is that the balance between LR and RR is wrong when I get on the gas.

You could also leave it like it is and limit up travel with a limiting chain like on the LR.
But if you have a lot of up angle, in top bar, that may be why the rear end squirts out on throttle. loading rr to quick

[rob burgoon]

You could also leave it like it is and limit up travel with a limiting chain like on the LR.
But if you have a lot of up angle, in top bar, that may be why the rear end squirts out on throttle. loading rr to quick

That's not a bad thought, chaining the RR, then you can dictate the final dynamic bite while on the gas hard.

In all conditions I believe the rear likes to squirt out if you gas it early and mid corner, but when the track has been watered better the rear seemed to take the power well on exit. I'm happy to try less RR upper bar, but I worry that will make the midcorner push worse and make the exit worse too since the RR coming up later means the rear steer stays around later in the corner.

[stock car driver]

rr chain only works on a smooth track it will make your car dump truck tight if theres moisture

[JustAddDirt]

rr chain only works on a smooth track it will make your car dump truck tight if theres moisture

True, but mine are adjustable, so when track is wet I loosen chain up, as it slicks off It tighten it up. I have marks for the sweet spots on both lengths.

[powerslide]

how much difference between the two marks JAD?

[rob burgoon]

True, but mine are adjustable, so when track is wet I loosen chain up, as it slicks off It tighten it up. I have marks for the sweet spots on both lengths.

Looser RR chain means when on the gas hard, rear weights closer to equal, tighter RR chain means more LR bite (weight bias)?

Or is it just poor performance over bumps with a shorter chained RR when on the gas hard?

[JustAddDirt]

how much difference between the two marks JAD?

bout 1"
when track is slick I have very little slack, chassis will move up maybe a shade more than 1/8 before chain gets tight.

I loosen it up when track is rough/wet.

I have done it several ways:

1/2" X 5"bolt with a chain welded to it going down to rear end.
on chassis have a tube going threw frame rail, or welded to side of rail with a 1/2" ID (like a leftover piece of steering shaft tube) use a locknut on top to adjust up and down on threads of 1/2 bolt. I mark the bolt with the 2 heights with a piece of electric tape around the 1/2" bolt.

[JustAddDirt]

Looser RR chain means when on the gas hard, rear weights closer to equal, tighter RR chain means more LR bite (weight bias)?

Or is it just poor performance over bumps with a shorter chained RR when on the gas hard?

1. yes, essentially..When car climbs on bars on rr it is planting the RR tire harder.

2. when chained down on RR in rough/wet tire will not conform to bumps or run in track as well, and tends to hop the RR, because of no drop (rebound)
Also, when chained down it tries to plant the LR harder till it maxes out travel. (may cause push when throttle first applied, which is also about mid corner and it will shove nose up track)

One think you never want is a tight racecar with a crate motor.

[powerslide]

Thanks JAD we will give that a try sometime this season.

[stock car driver]

True, but mine are adjustable, so when track is wet I loosen chain up, as it slicks off It tighten it up. I have marks for the sweet spots on both lengths.

of course it is adjustable all of ours are adjustable. I used old school wrenches for a while on all thread but have this now.. http://www.speedwaymotors.com/Wehrs-Machine-Quick-Change-Limit-Chain-Adjuster-IMCA,112640.html much easier to just pull the pin when you need to adjust the drop or adjust bars and need the spring unloaded...

for the track he was on it would be junk tightened up on rr

[rob burgoon]

Gonna reduce the RR upper angle one big hole for saturday. I'll order a second chain if this doesn't go the way I expect.

[rob burgoon]

Lots of crashing this time around. These cars are amazingly tough or I'm just amazingly lucky. All the crashing made it hard to focus on setup.

http://youtu.be/upp-VDbcqzM
http://youtu.be/1sPYMz49pVU

The track blacked over pretty fast in the main. Very tricky to drive the car in the black. Do you guys have any theories on how the car's behavior changes in the black? Does tread depth matter in the black? Sipes help? Hurt? Bring out the worn tires for the black maybe?

When cornering does having the tire press down still increase grip in the black, or does it flip-flop since the surface is harder?

Lateral G and weight transfer seems to go down in the slick, does that mean we want to increase on-throttle dynamic weight on RR a little when we hit the gas? Maybe incline a RRU a little in the slick and lower it a little in the tacky to adjust for this?

[drtrkr244]

Your car looked very loose in and off. The track looked fairly hard and slick. Generally, you have to increase weight transfer to the right side tires to generate more side bite and forward bite, esp when using harder tires.

My go to adj for those conditions are 1) lower jbar on pinion 2) lower right bottom bar 3) lower right top bar 4) lengthen drop on LR. Just be careful not to get too tight as that would kill a crate car. Hope this helps.

[rob burgoon]

You race with some idiots. Wow, talk about talentless haha. These guys can't even keep the cars under them! I wouldn't race there unless you plan on getting wrecked weekly. Looked like every car except 1st and 2nd spun hahaha 

Eh, I can't really complain. A car got wiped for the night from one of my spins in the heat, and then I managed to back into someone's undamaged panel. Oops. Still adjusting to the no mirror thing haha, thought I had seen every car involved, but was mistaken.

More lessons learned.

[rob burgoon]

Your car looked very loose in and off. The track looked fairly hard and slick. Generally, you have to increase weight transfer to the right side tires to generate more side bite and forward bite, esp when using harder tires.

My go to adj for those conditions are 1) lower jbar on pinion 2) lower right bottom bar 3) lower right top bar 4) lengthen drop on LR. Just be careful not to get too tight as that would kill a crate car. Hope this helps.

Here's my guess at the primary effects of each of those:
1) lower rear roll center, more body roll, more weight transfer to RR when cornering
2) less rear steer, does something to entry maybe?
3) less weight on RR when on gas, less rear steer
4) more rear steer, more weight on LR

Lot going on there if I have it right.

Also, after that race that was 2 nights on the same tires, LF 5/32, RF 4/32, LR 3/32, RR 2/32 tread depth of the paddles. add 2/32 for tread depth of the circumference cuts. I was running about 13 psi cold all around, tire wear suggests less pressure on right side tires and a little less on left side. I might try 11 on the right sides, 12 on the left.

[oldtrackchamp4x]

RF 12 RR 11 LF 10 LR 8 Dry slick only.JMO.

[rob burgoon]

RF 12 RR 11 LF 10 LR 8 Dry slick only.JMO.

Do you have a theory on why the lower pressures on the left side? Do the rights have to be higher to keep the tire on the bead or something?

3 psi split on the rear tires to add stagger?

[oldtrackchamp4x]

This is what Hoosier tire recommends for their G-60 IMCA tires on a dry slick track. Except the RR. They say 12 but I run the RR at 11 and it works for me. JMO.

[stock car driver]

This has to be a joke, you've got the internet and found this forum but you cant find shaw, jet or many of the other chassis websites with set up and tech adj guides?

[rob burgoon]

This is what Hoosier tire recommends for their G-60 IMCA tires on a dry slick track. Except the RR. They say 12 but I run the RR at 11 and it works for me. JMO.

Fair enough.


This has to be a joke, you've got the internet and found this forum but you cant find shaw, jet or many of the other chassis websites with set up and tech adj guides?

How many setup guides describe why lower pressures on the left side are favored? Do post a link if you can find one that says *why* lower pressures on the left are better.

[stock car driver]

Fair enough.



How many setup guides describe why lower pressures on the left side are favored? Do post a link if you can find one that says *why* lower pressures on the left are better.

really? you need someone to tell you that. like I said I hope your just screwing with everyone on here, nobody can be that out of it.

[stock car driver]

http://www.hoosiertire.com/otdtire.htm


12. IMCA Air Pressure Siping & Grinding Tips

1) What is the proper air pressure for the IMCA tire?
a. Temperature profile across the tire is the best indicator
- If your temperatures are even across the tread, your pressures are correct
b. We always recommend running the most pressure possible
- Under inflated tires will feel soft, squirmy, unresponsive
- Over inflated tires will be loose with little traction, “on top of the track”
c. Standard IMCA Modified setup:
- Heavy Track - 15 right side, 12 left side
- Slick Track – 14 right front, 10 left front, 13 right rear, 8 left rear

2) How should I sipe my IMCA tires?
a. Why do we sipe?
- To build or remove heat
1. We sipe across a tire to increase wear and build heat. We sipe around a tire to reduce heat and increase sidebite when additional traction is not necessary.
- Reduce block stiffness and increase wear on tires too hard for track conditions
b. Siping tips
- We generally never sipe more than ½ depth of any block. 1/3rd the depth of the block, or 3/32nds, is preferred in most situations.
- The more sipes you apply, the shallower they should be. In turn, the less sipes you use, the deeper you can cut while still minimizing the risk of chunking.
- The more evenly you can space your sipes within a block, the better their performance will be. You should always try and limit the amount of small, unsupported corners of a block to reduce tread chunking.
- Unless facing severe track conditions, IMCA tires seem to like aggressive siping, both across and around, the tire. In turn, if the track is severe, only shallow, circumferential sipes should be used to help reduce temperature and possible tread blistering. Taylor your quantity and location of sipes to the track conditions; the easier the track, the more sipes and vise versa.

[rob burgoon]

Don't mind this idiot ^ he can't keep his car consistent if his life depended on it. Just time the moron and you'll see this. He is way behind. His stock car days makes his head all big and mighty when in reality he only bully's over the Internet and a coward in person. He unlocks and blocks me regularly because he wants to know what I say. That should tell you Enough about the creep.On another note tire pressures we personally even out when track slicks off. Close up rear pressures and fronts. Stock car doesn't know his RR temp or pressure when he gets off track and likes cooking it cuz he has no talent obviously. Like I said time the talentless idiot who has no one backing him.

Yeah, he doesn't seem to play nice in other threads either. He sent some abuse my way in private messages.

At any rate, the tentative plan for next week is to rotate the tires around, buy a belt sander, and try to knock off some shine. It will be night 3 on that set, and I expect the track to get blacker in the main. I'll add some stagger to try to remove the desire to slide in the middle of the corner. Driver will try to take up the gas again earlier to stabilize the handling.

[stock car driver]

Yeah, he doesn't seem to play nice in other threads either. He sent some abuse my way in private messages.

At any rate, the tentative plan for next week is to rotate the tires around, buy a belt sander, and try to knock off some shine. It will be night 3 on that set, and I expect the track to get blacker in the main. I'll add some stagger to try to remove the desire to slide in the middle of the corner. Driver will try to take up the gas again earlier to stabilize the handling.


Your funny. I tried to help you. CLEARLY your just screwing with people on here nobody is stupid enough to not know why the left side air pressure is lower on a car turning left.

9x cant make up his mind, first hes a old old wise crew chief, then hes a crew guy whos been around dirt track racing longer than Ive been alive, now hes a driver, he needs to try and keep his lies straight hes posting on here.

[rob burgoon]

Your funny. I tried to help you. CLEARLY your just screwing with people on here nobody is stupid enough to not know why the left side air pressure is lower on a car turning left.


You have no idea either, so beat it.

[stock car driver]

Yeah, he doesn't seem to play nice in other threads either. He sent some abuse my way in private messages.

At any rate, the tentative plan for next week is to rotate the tires around, buy a belt sander, and try to knock off some shine. It will be night 3 on that set, and I expect the track to get blacker in the main. I'll add some stagger to try to remove the desire to slide in the middle of the corner. Driver will try to take up the gas again earlier to stabilize the handling.


You have no idea either, so beat it.

I posted right off hoosiers website for you, it clearly states why and how to determine air psi per tire. Its not rocket science.

[oldtrackchamp4x]

I made a mistake when I posted the tire pressures that I said Hoosier recommends. All I had to do is look at my copy of their sheet but I didn't. Trusted my memory. My mistake. But, like I said, the pressures I posted work for me. JMO

[rob burgoon]

I posted right off hoosiers website for you, it clearly states why and how to determine air psi per tire. Its not rocket science.

It says how much and how to tune, it doesn't say why the left side is different, or why the difference in pressure front to rear.

[stock car driver]

Over inflated tires will be loose with little traction, “on top of the track”

1) What is the proper air pressure for the IMCA tire?
a. Temperature profile across the tire is the best indicator
- If your temperatures are even across the tread, your pressures are correct


Everyone knows a tire with more foot print will give more traction and everyone knows a left side tire on a car turning left doesn't have near the load of a right side tire, lol..

I guess you prove that you can lead a horse to water but cant make it drink adage.... Over and over people on here give you the information you need but you choose to be confrontational and want to argue about it. .. proving my point your not really here to learn a thing, your here to stir the pot like 9x who cant even remember all the different lies hes told on here.

[rob burgoon]

Over inflated tires will be loose with little traction, “on top of the track”

1) What is the proper air pressure for the IMCA tire?
a. Temperature profile across the tire is the best indicator
- If your temperatures are even across the tread, your pressures are correct


Everyone knows a tire with more foot print will give more traction and everyone knows a left side tire on a car turning left doesn't have near the load of a right side tire, lol..

I guess you prove that you can lead a horse to water but cant make it drink adage.... Over and over people on here give you the information you need but you choose to be confrontational and want to argue about it. .. proving my point your not really here to learn a thing, your here to stir the pot like 9x who cant even remember all the different lies hes told on here.

First paragraph is an effect, not a cause. Second paragraph is an effect, not a cause.

Third paragraph, holy crap, you just offered up a theory on why. Now if we have the bars and bite set to balance the weight on each of the rear tires at corner exit, why does the LR get so much less pressure? Wouldn't it get the same pressure as the RR since it has the same weight on it at exit?

[Dirtmod13]

First paragraph is an effect, not a cause. Second paragraph is an effect, not a cause.Third paragraph, holy crap, you just offered up a theory on why. Now if we have the bars and bite set to balance the weight on each of the rear tires at corner exit, why does the LR get so much less pressure? Wouldn't it get the same pressure as the RR since it has the same weight on it at exit?Less pressure to make larger contact patch which gives more traction. It's a simple way to get more use out of that tire

[Confused?]

The rear tires are not equally loaded on exit. That would be true IF the car was headed in a straight line, but it's not. It's still turning as you are picking up the throttle. Generally, the LR tire will be loaded more than the RR, under acceleration. Think of it this way, if 500lbs are transferred to the rear, do you want 250lbs on each tire? Or would you rather have 350 on the LR and 150 on the RR? The extra load on the LR helps it "break" through the dust and gain traction.

The right side tires have more air because there is more lateral loading than the left side. The left side, usually has less because because of increased footprint and deflection. A loaded LR, with a low air pressure, will wrinkle the side walls like a drag slick. This aids in maintaining traction under throttle. Think about how a drag slick works.

The air pressure affects wheel weights, but more importantly, affects sidewall and tread deflection. What works for me may not work for you. I like to run 16 on the rights and 12 on the lefts in the tack. For dry, I drop the rights to 14 RF and 13 RR. The left I will drop to 10 for both tires. That change will affect the LR bite in your set-up. You need to know what other changes to make after dropping the air pressures.

Hope this makes it a little more clear.

[rob burgoon]

Less pressure to make larger contact patch which gives more traction. It's a simple way to get more use out of that tire

Sure, but why not less pressure on the right side tires then? Traction is good!


The rear tires are not equally loaded on exit. That would be true IF the car was headed in a straight line, but it's not. It's still turning as you are picking up the throttle. Generally, the LR tire will be loaded more than the RR, under acceleration. Think of it this way, if 500lbs are transferred to the rear, do you want 250lbs on each tire? Or would you rather have 350 on the LR and 150 on the RR? The extra load on the LR helps it "break" through the dust and gain traction.

The right side tires have more air because there is more lateral loading than the left side. The left side, usually has less because because of increased footprint and deflection. A loaded LR, with a low air pressure, will wrinkle the side walls like a drag slick. This aids in maintaining traction under throttle. Think about how a drag slick works.

The air pressure affects wheel weights, but more importantly, affects sidewall and tread deflection. What works for me may not work for you. I like to run 16 on the rights and 12 on the lefts in the tack. For dry, I drop the rights to 14 RF and 13 RR. The left I will drop to 10 for both tires. That change will affect the LR bite in your set-up. You need to know what other changes to make after dropping the air pressures.

Hope this makes it a little more clear.

At corner exit, you're still turning as you feed in the power, so you still have weight transfering to the right side and the RR. To keep the RR from getting overloaded, you use bite and bars to add weight to the LR. I'd expect them to be equalish once all is said and done. However, if what you're saying about more total load on the LR than the RR helping it push down through the dust is right, why wouldn't he same be true for the RR pushing down through the dust if we let the RR stay really heavy?

For lateral loads, that makes some sense. If the right side tires are experiencing more load, I could see an issue where lack of sidewall stiffness becomes a problem. That might explain the higher pressures for tacky tracks.

Great post! Thank you!

[powerslide]

Side walls do not have grooves that is why you can only go so low on right side pressure, also the driver stops feeling the changes when you get too little air in the tires.

[Confused?]

The RR is heavy, as you put it, during the corner. That is also why the trend towards stiffer RR springs than LR. The weight is transferred to the right during cornering. To offset that, more angle in the bars, more indexing, more LR bite, and less air are used. Typically, you would not want to drive off the RR in the slick. It causes the car to loosen up on exit. In the tack, sure, but not dry slick. Equalizing the rear wheel loading happens down the straight. Or, it should. That's where you should feel the RR starting to raise up, if the chain allows it.

At corner exit, the weight should already be on the right side. As you pick up the throttle, the weight starts to move to the rear. The LR get loaded more due to bar angles and roll steer.As the car travels down the straight, the weight starts to move back towards the left side of the car. Think of the weight, during racing, as being a liquid. It get slung all around the car. The driver is the one who tries to control it and "put" it where he/she wants it.

Everything that is designed into one of these cars is done for a specific reason, at a specific point on the track. They are all "matched" together, as a compromise, to make the car work everywhere. That's why you don't run the same bare angles on the right side as you do the left. Also why we run a j-bar rather than a watts linkage. Air pressure are just one more variable in the mix.

If you can find some books on Late Models, it may be worth your time to read them. The rules for those cars apply to Mods as well.

Good luck

[rob burgoon]

I've got this one and have read through it a few times. Good stuff but kind of light on the "why" sometimes.

http://www.amazon.com/DIRT-MODEL-CHASSIS-TECHNOLOGY-MANUAL/dp/B00QVBTSAA

[rob burgoon]

The RR is heavy, as you put it, during the corner. That is also why the trend towards stiffer RR springs than LR. The weight is transferred to the right during cornering. To offset that, more angle in the bars, more indexing, more LR bite, and less air are used.



So we want the pressure as low as we can get it until the footprint goes to crap. Too much lateral load does that. In the middle of the corner, the right side tires have most of the lateral load and as such, those pressures need to be higher to help stay off the sidewall. Then, at exit, we have decreasing lateral load and want to go forwards. At this time, the LR being low pressure is a good thing since tire crinkle is good when you're pretty much going straight.

The only problem with that theory is the fact that the LR is up half a foot in the air almost the whole corner and carrying a fair amount of weight. Maybe the RR still carries more midcorner despite that?

[Confused?]

The LR is up half a foot? Are you referring to the chassis? If your tire is up, then you have other problems. The chassis should be up on the left rear. It's a bi-product of the weight transfer and suspension designs. About the only times the RR is loaded more than the LR is entering and through the center of the corner. That's where you get the sidebite from, loading the RR enough to plant it to the track's surface. If the car is set-up correctly, and the driver is doing his/her job, the RR will be the most loaded tire in the center of the corner. The RF will be at entry and weight should be shifting to the LR at exit.

Too low air pressures can also create too much heat in a tire. The same is true for too much air. A friend of mine runs 12 on the right and 10 on the left for all conditions. He has a few IMCA national championships. I respect his opinions very much. Generally, I, as well as most, lower the pressures for dry slick because you don't carry as much speed into or through the corners. Traction is hard to find and the lower pressures help with that. Also as said above, there are no treads on the sidewalls. The air needs to be high enough so that you aren't running on the sidewalls.

[oldtrackchamp4x]

A good way to see if your right side pressures are to low is to take a marker, white shoe polish works well, and mark from edge of tread toward wheel in a few spots. That way you can visually see how far tire is rolling under. Do the same on the left side tires but mark on the inside.JMO.