Too much roll stiffness?

[Nessumsar]

That is what I have been throwing around in my head about my Nova. My car seems to push pretty badly, and I would like to attribute it to too much front-end roll stiffness. My current setup is:

Front:
Hotchkis springs, gas-adjusts, poly bushings, and an Adco 1-1/8" solid bar. With 245 Nitto 555r

Allignment is -1.5* cam., ~4.5* caster, and 1/8" toe in.

Rear:
Hotchkis leafs, and gas-adjusts, and no bar. With 285 Nitto 555r.

And an Iron/Iron small block.

I also have no sub-frame bushings, which brought the front of the car down ~3/8". Couple that with not having any of the heater elements (even controls and heater core box), or blower motor assembly, and just front seats. I have a feeling that with the front bar being solid and lack of front end weight, it is providing too much stiffness.

What do you think?

[sik68]

Under what conditions does it push? Street, AutoX or Road Course?

I don't think my understeer as as bad as yours, but I am definitely in a push on a track. I think you gotta work on front suspension geometry: upper control arms, maybe a taller spindle will help the camber curve. I've also been told to really crank up the camber for the track. I was at -1.0 deg, and need to go up to -2.5 to -3 degrees if possible.

Concerning roll stiffness, I've also been told that you can replace 1 or more of the front sway bar poly bushings with rubber bushings to soften the effective rate of the bar. It's a cheap way to dial out some roll stiffness.

[parsonsj]

A 1 1/8 front bar with no rear bar = push.

I'd also consider less toe-in (maybe up to 1/16 toe out) for easier turn in. That will help you to get the car to rotate and might feel a lot better without spending money on a rear bar.

jp

[Nessumsar]

A 1 1/8 front bar with no rear bar = push.

I'd also consider less toe-in (maybe up to 1/16 toe out) for easier turn in. That will help you to get the car to rotate and might feel a lot better without spending money on a rear bar.

jp

Won't that just affect how quickly the car responds to input? Will it provide more from end bite?

And Sik, I have rubber mounts on the bar already.

It pushes pretty much anytime I drive it hard, but more noticably on tight auto-cross.

I was thinking more along the lines of switching to a hollow 1-1/8" bar? And maybe add a small bar in the rear? I can get my hands on a stock 4th gen F-body rear bar, I forget how big they are though...

[sik68]

I was thinking more along the lines of switching to a hollow 1-1/8" bar? And maybe add a small bar in the rear? I can get my hands on a stock 4th gen F-body rear bar, I forget how big they are though...


I think if you add a rear bar without correcting the problems at the front, you are balancing the car's handling by reducing traction at the rear to match the lack of traction at the front. Sure it will feel more balanced, but in a lower state of overall grip. So, depending on the definition of "handling", it may handle better, but perform worse.

[Nessumsar]

I wouldn't add a rear bar without changing something first.

I will try changing up the alignment first, but I don't think that will be enough to counteract the understeer.

If I did switch to a hollow bar, should it be of the same size? Or should I move down to a 1"? Maybe move to a 1" and add a small rear bar to keep the total roll stiffness up?

[parsonsj]

That will help you to get the car to rotate
Won't that just affect how quickly the car responds to input? Exactly.

As for correcting the push, sounds like you're on the right track.

jp

[sik68]

Please post a followup after you do the alignment and your future changes as well. I am curious to hear how much of an effect it has on your handling. with -1 camber on my car, i was only using about 80% of the front tires' width going around corners. I had the tire wear patterns to prove it; my 245's became 205's around a corner. I'd love to also learn about how a your playing with sway bars affects understeer as well.

-Steven

[Nessumsar]

With the allignment specs listed, at RTTC the tire was wearing right to the edge of the tread. I was getting all I could out of the tire. Which is what leads me to beleive it is a roll stiffness problem...

Those are the specs that David Pozzi has listed on his site for a 1st gen Camaro w/o Gulstrand mod.

[zbugger]

Jon, to keep it easy get an adjustable rear sway bar. A hollow 1 1/8" front bar is about equivalent to a 1" solid bar, so going hollow there would soften things up a bit. With the adjustable rear bar you can tune out some of the push. The rest may come with adjustable shocks and playing with your tire pressures.

[David Pozzi]

Jon.
You can increase positive caster to 5 deg positive.
Toe in can be reduced to near zero but you aren't going to notice any handling difference with any of these changes from where you are at now, they are too minor. One thing you will see is if the car has settled at all since your last alignment, the toe in will have increased a LOT due to the large amount of bumpsteer these cars have.

The 1 1/8" solid front bar is HUGE on a 1st gen/Nova sub! I don't think there is a rear bar made that would be stiff enough to work with it. The adco bar is made to work with stock springs, so when stiffer springs are added, it's way too stiff in roll.

Since you have Hotchkis springs, their bars would come closest to working well in a balanced package for you. A rear bar is a must, if you don't like the exhaust clearance of the narrow Hotchkis bar, their 2nd gen Camaro rear bar will fit.
David

[MrQuick]

I agree, 1" solid max on these 1st gen F-X body frames and I would recommend a Speedtech/ATS tall spindle for it. Huge improvment for these cars over stock.

Go for the 2nd gen bar and add the adjustability to the mix.


Vince

[JRouche]

IMO yer push is coming from the un-balanced car. You have a decent amount of front stiffness, I wouldnt change that. Its not too tight. But the back is too loose. No bar.

A light rear (rear roll stiffness) will exaggerate the front roll stiffness. So the front will push. Its taking all the lateral loads so it will be heavy at the front.

Want to lighten it up at the front a lil? So the front isnt pushing so much? Put a rear bar in there.

Pull the rear inside tire down some and the front outside tire wont see so much of a load. Reduced push.

Now to an extent. You will skip the front loaded (outside) tire across the pavement if you arent careful. Then you are getting into oversteer. The front is too light and skipping over the road surface and the rear is firmly planted till she breaks loose.

Now thats fun driving. I like an oversteering car. Just my thing. Well hell, I like an understeering plow too!! They are more predictable. I have pushed a few heavy understeering cars through the traps. Not as stressful.

On the edge, a nice light (oversteering) car. Fun on a track, kinda fun till the rear end comes around on the street.

Just about balance I think. JR

[CarlC]

A solid 1-1/8" bar is close to twice the stiffness as a typical hollow 1-1/8" bar. You've got double what Hotchkis intended for that spring.

With the Guldstrand mod, even with -2* camber, outside tire wear is still a problem.

[Nessumsar]

Thanks for all of the input guys, I will see about switching out bars. Looks like a Hotchkis front and rear bar in my near future!

[pitts64]

Do you have the poly end link bushings on the bar too tight...

[jay72nova]

Thanks for all of the input guys, I will see about switching out bars. Looks like a Hotchkis front and rear bar in my near future!

sounds like that will balance things out...good thread!

[GrabberGT]

I dont see it mentioned on here yet and its kind of a "doh!" kind of comment but... are you on the bump stops when hard cornering. I have a similar problem and think that is the primary contributor.

[jay72nova]

I dont see it mentioned on here yet and its kind of a "doh!" kind of comment but... are you on the bump stops when hard cornering. I have a similar problem and think that is the primary contributor.

you could be right but honestly I don't think he would have to be with that Parthenon Column he's got up front there!



With the Guldstrand mod, even with -2* camber, outside tire wear is still a problem.

HUH, I myslef am only running -1* maybe I should turn it up..shoot I'll get some caster out of it too!!! what do you recommend? I guess I could just turn it up until I get inside wear....i still need to install my overlength balljoints.
sorry don't mean to change the topic....

[jay72nova]

sorry double post

[rustomatic]

Do you have any rear axle lateral location? Someone more technologically conversant that I should be mentioning finding a roll center here. I would say that with a rear bar (of any significant size), you'll be going from the plow to the Dukes of Hazzard driving style, which isn't altogether un-fun... After ignoring axle location for sway bars on the rear axle for years (and sliding/drifting rears), I've found a whole new world of fun input with a good Panhard setup...