Left rear in front

[Dirtmod13]

New class for our track is making us run our spring and shock in front of the axle on the left rear. How can I get back some of that traction that will be lost

[Matt49]

What type of rear end and suspension cage?
Assuming you are running something that allows for axle wrap under acceleration, you will get better traction clamping your shock mount to the axle tube versus having the shock on the birdcage.

[MasterSbilt_Racer]

Agree with Matt. Clamp and very soft spring.

[Dirtmod13]

Agree with Matt. Clamp and very soft spring.Car is an '09 rocket wide blue front. All rocket parts. Was super late model. Has quick change with rocket birdcages. Only change/ rule is all cars must have one coil over shock in front of left rear. Here's the rule.8.1 4-Bar and Z-Link only rear suspensions allowed. Left Rear spring must be mounted on front side of rear end to birdcage.Doesn't say any rule for right spring.

[Matt49]

Car is an '09 rocket wide blue front. All rocket parts. Was super late model. Has quick change with rocket birdcages. Only change/ rule is all cars must have one coil over shock in front of left rear. Here's the rule.8.1 4-Bar and Z-Link only rear suspensions allowed. Left Rear spring must be mounted on front side of rear end to birdcage.Doesn't say any rule for right spring.

Obviously you didn't write the rule so this isn't directed toward you but this is pretty high on the list of dumbest rules ever written. What does that accomplish?
And for what it's worth, the way it is written, you can't even run a spring mount clamped to the axle tube.
Not to get off on a tangent but far too many people writing rule books these days no far too little about racing.

[Matt49]

Out of curiosity, what track is this and what are they calling this class?

[Dirtmod13]

Out of curiosity, what track is this and what are they calling this class?Track is in Wisconsin. Mississippi thunder speedway. Class is new USRA limited late model. We just moved up from Bmods. From what I've heard, the move to the front on LR was to limit traction and make the older cars able to compete if some one was to buy a brand new chassis.

[RacerX10]

Obviously you didn't write the rule so this isn't directed toward you but this is pretty high on the list of dumbest rules ever written.

I was thinking the same thing :)

[MasterSbilt_Racer]

Obviously you didn't write the rule so this isn't directed toward you but this is pretty high on the list of dumbest rules ever written. What does that accomplish?
And for what it's worth, the way it is written, you can't even run a spring mount clamped to the axle tube.
Not to get off on a tangent but far too many people writing rule books these days no far too little about racing.

It is based on the belief that the spring behind has ruined racing by hooking the cars up too good.

To defeat this rule, run z link. Top bar around 34" long, 15 degrees downhill to the back. Bottom bar in the highest hole for the 4 link deal. Coilover on front of cage. Make sure you have a clevis mount and that the coilover is forward enough to not crash into axle tube. That will give you a similar wheel rate to doing a lr behind deal.

[Matt49]

Track is in Wisconsin. Mississippi thunder speedway. Class is new USRA limited late model. We just moved up from Bmods. From what I've heard, the move to the front on LR was to limit traction and make the older cars able to compete if some one was to buy a brand new chassis.

If that's their reason that's pretty ignorant. Any older car can be made to run with the LR behind with a little fabrication.
Rules that restrict ingenuity never save anybody money.

[let-r-eat]

Another racing rules committee that doesn't realize it takes more than the left rear of a car to make one go.

[TheJet-09]

I'll try to describe a LR set-up I saw on a car at Brownstown around 2000 or so (I don't remember who it was, but if Matt49 was around back then he might). The LR birdcage was two independent pieces, with the outer half having two links mounted to it (normal configuration, running forward) and the inner half having the spring/shock mounted to it, in front. From that inner half was a link mounted to the bottom that ran forward/angled upward to the chassis. When the LR lifts in the corner (and under acceleration), the mounting point (chassis end) of that link also raises, which in turn rotates the bottom of that half of the birdcage up, thereby keeping a load on the spring (or at least diminishing the loss of the spring load when compared to that of the old style birdcage with the spring in front). If it sounds like that would work, I could try drawing a picture to make it clearer. Thoughts?

[Dirtmod13]

I'll try to describe a LR set-up I saw on a car at Brownstown around 2000 or so (I don't remember who it was, but if Matt49 was around back then he might). The LR birdcage was two independent pieces, with the outer half having two links mounted to it (normal configuration, running forward) and the inner half having the spring/shock mounted to it, in front. From that inner half was a link mounted to the bottom that ran forward/angled upward to the chassis. When the LR lifts in the corner (and under acceleration), the mounting point (chassis end) of that link also raises, which in turn rotates the bottom of that half of the birdcage up, thereby keeping a load on the spring (or at least diminishing the loss of the spring load when compared to that of the old style birdcage with the spring in front). If it sounds like that would work, I could try drawing a picture to make it clearer. Thoughts?That would be cool, send pic to my email, custombuildremod@yahoo.com

[drtrkr244]

That sounds like the TWM cages built for GRT. You could lock the two halves together with the bolt supplied. But you had to drill and tap a bolt into the tube if you ran it "clamped". I knew a local racer that ran this with 150lbs bite and 250lr spring.

[TheJet-09]

Exactly! That's what I just remebered (the style of birdcage). So from the half with the spring mounted to it, you would run a bar forward to the chassis. It would obviously require you to weld another lower link mount to the chassis (inboard of the existing one).

[RacerX10]

3 months before the season starts, and you guys have worked around the new (stupid) rule already :)

[Dirt2727]

Just put a short straight panhard bar on it..and with todays shock packages it will fly, and have plenty of traction

[BWRC_6M]

u guys diont get it, its a great rule they rules allow certain 4 shocks they can run they cost about 90 a piece ok so if u go spring behind that means u will spend money for a good LRF shock to conrtol the car has we know, b with the limited motor rules with spring in front of the axel that is way less strain on the motors saving the racers money, before u carve up the track for coming up with this class which has a lot of ppl talking about it and racing it that kind of thinking is why the expense of racing is so high

[SLM98]

Before the days of LR shock behind cars we ran the LR clamped to the axle in front and the RR clamped behind the axle. We controlled traction off the torque arm. We lapped the field in a 35 lap feature with this setup

[hpmaster]

Sounds to me like some track owner longs for the days of no side bite tail out 65% rear weight 1990's racing. Maybe I can make a comeback?

[Dirtmod13]

Before the days of LR shock behind cars we ran the LR clamped to the axle in front and the RR clamped behind the axle. We controlled traction off the torque arm. We lapped the field in a 35 lap feature with this setupWhat did you do with the torque arm to gain traction?

[MasterSbilt_Racer]

What did you do with the torque arm to gain traction?

What he means is that the more the torque arm moves, the more dynamic wedge the car picked up.

[Dirtmod13]

So with the rule of having the shock/spring ahead would this work?Pic is 90* off but you get the idea. It would allow birdcage to index into the front spring.

[MasterSbilt_Racer]

So with the rule of having the shock/spring ahead would this work?Pic is 90* off but you get the idea. It would allow birdcage to index into the front spring.

That way downhill bar will kill forward bite.

[TheJet-09]

I'd be curious to see how they actually interpret/enforce their own rule. With the spring having to be mounted "to the birdcage" does that mean you can't clamp it to the tube? And if it has to be a 4-Bar or Z-Link, I guess my suggestion would actually be a 5-Bar?

[V1SLM]

We ran the LR clamped up for years in the early 2000's. The car was as fast as they are today when you are out of traffic, the car would 3-wheel like crazy, but man was it fast when you where out front!

[TheJet-09]

Did you run a 90/10 on top of the rearend to control it going into the corner? I vaguely remember those days. Seems like they would "crash" down when you let off. I also like the short, straight panhard bar idea!

[Dirtmod13]

Did you run a 90/10 on top of the rearend to control it going into the corner? I vaguely remember those days. Seems like they would "crash" down when you let off. I also like the short, straight panhard bar idea!I thought I saw a jbar rule mentioned. Was frame mount on left and over driveshaft to rt side of pinion. But read through 2 times and can't find it now. Back to the x link in front, couldn't it be lowered to almost one point where both mount to frame to allow the birdcage to index into the frt mounted spring.

[hpmaster]

185lb spring clamped up on the LR in front, 90/10 on top of rear end, 275lb on RR in front, , 21" to 23" j bar, 40" lift bar 350lb spring on a dummy shock, chained limiter no 6th coil 550lb springs across the front turn off RF brake give it a bunch of rear % and go!

[Dirtmod13]

Ok so what about a 4 link like this?

[hpmaster]

Ok so what about a 4 link like this?

We ran both bottom bars down on the chassis about 5-degrees uppers 25+ left and right 18+, thats what we ran back in the day. As I think about it might have been a 225 spring on the right rear. Trycycling, hardly see over the hood but a ton of drive, if you didn't drive the he!! out of it, tail out it, rf brake off pushed like a dump truck, but a fast dump truck..

[fastford]

185lb spring clamped up on the LR in front, 90/10 on top of rear end, 275lb on RR in front, , 21" to 23" j bar, 40" lift bar 350lb spring on a dummy shock, chained limiter no 6th coil 550lb springs across the front turn off RF brake give it a bunch of rear % and go!

we won a fair amount of races back in 1999 - 2001 on that same basic set up , I think I wound up on a 400 rf though.

[V1SLM]

Almost the same set up as hpmaster...we ran LF 550, RF 500, LR 275 on clamp in front, RR 225 springs. Left side was 55%, rear was 54%, ran around 200lbs of bite, ran a 400lb 5th arm. Our left front was useless....

[Bcollins82]

I believe you guys are overthinking this a bit... I think the 5 link dual birdcage idea is kinda cool, but I don't think its really necessary. Look at how the rear mount reacts on the birdcage right now. It doesn't actually "push" the spring into the chassis, it just slows the rate that the LR spring is unloaded when the LR drops. By slowing down that motion it effectively softens your wheel rate on the LR. I would put the spring in front with an extra soft spring, or preferably a stack setup if the clamp bracket wasn't allowed. If the clamp is allowed, there's no reason to step back 15 years on your setup. Run a shock on the birdcage to control the LR timing, and put the spring on a clamp bracket. Cars now travel nearly as much on LR as they did back when people ran clamped up cars, but they don't have the attitude of the car above because of the more balanced package being run now with the cars being down on the RF, not rocked back on the RR.

[Dirtmod13]

Anyone got a pic of the clamp bracket? Rule states single coil over mounted to birdcage. So is the clamp on the tube or the birdcage?

[Dirtmod13]

Also, who are the off the wall crazy guys that have the real bad advice on this forum? Just so I don't waste a bunch of time listening to some goofball. Had a few on last forum that after reading it for a year it was easy to weed them out. I'm new to this forum.

[Bcollins82]

Anyone got a pic of the clamp bracket? Rule states single coil over mounted to birdcage. So is the clamp on the tube or the birdcage?

Clamp bracket clamps directly to the axle tube independent from the actual birdcage. You can probably find one on BSB's website. You'll probably have an easier time finding a pic of one in steel since mod guys are more apt to use them.

[drtrkr244]

The original TWM bcages were 2 piece. The inner half was the clamp bracket or you could put the bolt thru the bottom halves if you ran it conventional. We always threaded a bolt into the tube when we ran clamped up, just to make sure it didn't move.

[Bcollins82]

And for the record, this IS an idiotic rule... It will have little to no effect on how much horsepower you use. Someone did a test a few years ago and took the LR spring completely off the car and ran nearly identical lap times. The only effective way to limit these cars at this point without sending everyone running to their chassis builder is to limit rear suspension down travel. Good luck finding a sanctioning body that will enforce that one... Lol

[MasterSbilt_Racer]

I believe you guys are overthinking this a bit... I think the 5 link dual birdcage idea is kinda cool, but I don't think its really necessary. Look at how the rear mount reacts on the birdcage right now. It doesn't actually "push" the spring into the chassis, it just slows the rate that the LR spring is unloaded when the LR drops. By slowing down that motion it effectively softens your wheel rate on the LR. I would put the spring in front with an extra soft spring, or preferably a stack setup if the clamp bracket wasn't allowed. If the clamp is allowed, there's no reason to step back 15 years on your setup. Run a shock on the birdcage to control the LR timing, and put the spring on a clamp bracket. Cars now travel nearly as much on LR as they did back when people ran clamped up cars, but they don't have the attitude of the car above because of the more balanced package being run now with the cars being down on the RF, not rocked back on the RR.

Not really. The dynamic wheel rate is as important, or moreso than the wheel rate at ride height.

[Bcollins82]

Not really. The dynamic wheel rate is as important, or moreso than the wheel rate at ride height.

Agreed. But the dynamic wheel rate with the spring behind is softer than the spring being used on that corner, if you don't account for the weight being transferred through the bars, only the spring. Softer rate=less spring rate unloading per inch of down travel, correct? So you would have to be extremely soft if you were in front to try and mimic the loading of the spring behind. I'm still not sure you could go soft enough in front to keep the load in the spring at dynamic height since the spring would unload so much faster in front. I'm sure you would have to use shock valving and bar angle as a crutch to help keep the car up and going.

[MasterSbilt_Racer]

Agreed. But the dynamic wheel rate with the spring behind is softer than the spring being used on that corner, if you don't account for the weight being transferred through the bars, only the spring. Softer rate=less spring rate unloading per inch of down travel, correct? So you would have to be extremely soft if you were in front to try and mimic the loading of the spring behind. I'm still not sure you could go soft enough in front to keep the load in the spring at dynamic height since the spring would unload so much faster in front. I'm sure you would have to use shock valving and bar angle as a crutch to help keep the car up and going.

Correct. But the front mount typically has increasing spring rate in rebound and the rear is decreasing.

[TheJet-09]

Maybe I'm misunderstanding something, but how can the spring in front gain rate (technically ride rate) during rebound if the upper and lower shock mounts are headed in different directions?

[Bcollins82]

Yep, MasterSbilt_Racer that is true. The curves would be complete opposites. You could increase lower angle, and decrease upper angle to help it some, while trying to keep thrust angles similar. You won't make it act completely the same with it in front, but from what I've experienced the amount of LR drop makes a much bigger difference than LR rate. I don't think anyone is going to switch it to the front and win a Lucas race, but this rule won't leave the cars flat and sliding either. IMO.. And Jet09. It's not that it gains rate as in loading the wheel, the motion of the front mount is faster than axle speed, making the spring act stiffer by loading faster in compression and unloading faster in rebound.

[TheJet-09]

Great suggestions by everyone and memories of things we used to run! What I don't understand is the intent of the rule. If it's engine related then address that. Make them run a 7000 RPM chip, or a 2-barrel. Don't Crate Cars run the spring behind? If it's to assist "older" cars I don't think they have an issue. LaSalle used to run a Limited class that was very competitive and not everyone had a brand name chassis. Even with the rule, where there's a will there's a way.

[LM14]

We were down to 125# spring on LR in front before spring behind caught on big. The soft spring and a short straight bar will make the car hike just like a spring behind car. You have to be careful with the short bar and make sure there are no binds anywhere.

SPark

[Dirtmod13]

With the short bar, does the chassis weight ( when rolled over)Push down on the left rear and drive that tire into the track tightening the car vs. using the jbar?Is anyone using the short bar now?

[Matt49]

Pretty much...The down side is that if you miss the setup you will have your hands full with a VERY erratic race car. There is a lot of sudden and sometimes unexpected movement with a short bar.

[hpmaster]

With the short bar, does the chassis weight ( when rolled over)Push down on the left rear and drive that tire into the track tightening the car vs. using the jbar?Is anyone using the short bar now?

The set up I put up earlier in this thread is one we used in the 1990's. The long J bar I listed as part of the set up gave you a slower reacting car. With a short bar and that set up I bet you would be heading in a very bad direction faster than the driver could react to it.

[Dirt2727]

But you need to remember we didnt have todays shocks back when we all were on the straight bar.

[MasterSbilt_Racer]

But you need to remember we didnt have todays shocks back when we all were on the straight bar.

You put a short straight bar on today's cars and you win the barrel roll contest. It was never a particularly good idea.

[lovinlatemodels]

A lot of great idea's on here but way to much thought going in to this. Probably the best car I ever had was my 99 Swartz which was built to a square tube chassis by our rules back then. Simple set up with a simple shock and spring package with a Z link RR and 4 Link LR. LF 550 Shock 5 valve, RF 350 shock 5 valve, RR 250 Shock 4 valve on the bird cage. LR Clamped 125 Shock 3 valve. % simple 53.5 L 54.0 R and we ran 10 lbs of bite. That car had great side bite and forward bite. The lift bar was simple also 33" with a 350 spring 3 valve shock and no preload and the J bar was simple 19" long with 6" split. This new class would be great for a financial stand point get rid of the high dollar shock package keep it simple put it back in the drivers hands not the check book.

[Dirtmod13]

Exactly. We were ready to buy a new modified chassis for the usra Bmod class we run up here in Minnesota Iowa and Wisconsin. Roller cost was $16,500Plus shocks, tranny , seat, motor etc. so easily over $20 k to get a new car out. We decided against that idea and bought an 09 rocket from a local shop for 9k with seat, trans, fiber driveshaft, everything but motor. Seems like a no brainer. When the track owner ran one at the last race of the season, he went out with the usra Amods. Started half a lap behind as to stay out of the way. Within two laps he was up to the Amods. Also he said the tires had 20 or more runs on them at 5-10 laps per run and still looked like new. American racer -56 compound. Must be hard tire.

[bullittwrench]

I'll try to describe a LR set-up I saw on a car at Brownstown around 2000 or so (I don't remember who it was, but if Matt49 was around back then he might). The LR birdcage was two independent pieces, with the outer half having two links mounted to it (normal configuration, running forward) and the inner half having the spring/shock mounted to it, in front. From that inner half was a link mounted to the bottom that ran forward/angled upward to the chassis. When the LR lifts in the corner (and under acceleration), the mounting point (chassis end) of that link also raises, which in turn rotates the bottom of that half of the birdcage up, thereby keeping a load on the spring (or at least diminishing the loss of the spring load when compared to that of the old style birdcage with the spring in front). If it sounds like that would work, I could try drawing a picture to make it clearer. Thoughts?

I had a 99 Bullitt with this deal on it. Ray called the bar that hooked to the inner cage with the shock/spring a bite bar. It worked pretty well but was very picky on bite bar angle.

[GRT62]

Straight bar with today's right side shocks=bent up roof and roll cage