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...Llar7QdjNkNbSQ

same race from the stands here:http://youtu.be/DW3e2IRhsko?list=UUC...Llar7QdjNkNbSQ

daytime here:http://youtu.be/2RA710EqdGI?list=UUC...Llar7QdjNkNbSQ

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.