My car seems to have a ton of rear steer. Seems as though I am chasing the rear axle through corners and over bumps. The front feels planted but the rear feels like it is wondering around. I have checked all the components on the car and everything checks out within specs. I planned on getting a adjustable Panhard bar as I know the Rear axle is shifted to the left side. So has anyone else ever had this type of problem and if so what route did they go about fixing it?

I bought this car a few weeks ago and having been fixing many of the problems the other owners have created. LOL So some info on the car it has 110,000 on it. The rear control arms have been replaced with BMI non adjustables other then that everything else is on the stock nature. It has 17x9 and 17x10 Z06 wheels on it but this problem happened when I had the stock 16" on there too.

I haven't had it aligned yet for two reason one I plan on lowering it this winter and I also want to make sure the rear axle is tracking correctly before getting it aligned.

Thanks for any information.
Jeff

 

Did you check the bushings on the panhard rod?

 

There's nothing to align on a solid axle with non-adjustable control arms anyway. Only the front end alignment is adjustable on a 4th gen, and even there it's camber and toe only -- caster is fixed.

 

Caster is adjustable on the front end of a 4th Gen. I run +4-deg.

The solid rear axle needs to be centered accurately, or the thrust angle is not going to be correct. It wouldn't make any sense to align the front end, knowing the rear end was not set up correctly.

 

Cool, I'm happy to be wrong about that one.

Is there anything you can do on a completely stock car to center the rear end, assuming all of the bushings/etc are in good shape?

 

No you can't center the rear axle without an adjustable panhard bar. Which is the reason I am holding out on getting it aligned. I am just trying find out if anyone has felt this type of problem and if so what was it. I think it is the panhard bar as it really feels like the rear axle is floating around back there. I can snap steer the car into either right or left direction causing the car to feel like it is pulling in the direction of input I throw at it.

 

bigJeff_SS:
If the car is still too loose, you could try a set of double adjustable trailing arms. They would enable you to increase the wheelbase as much as 2 inches.

 

After some searching on another forum board I have come up with a game plan. I plan on starting with an Adjustable Panhard Bar and replacing the rear shocks with something I will be able to use when I lower the vehicle. The rear shocks aren't leaking but they do look original and that alone is enough reason for me to change with something better. It does feel like the rear is getting into jounce to quickly due to the shocks not having enough compression. I haven't check the jounce bumpers yet either they may not be any good either.

 

Sounds like a panhard issue. See how much you can push the back of your side-to-side when its on the ground. It should only move as much as the bushings will allow which isn't much. If you can noticeably rock it side and side then there is an issue.

When installing your new panhard bar I would also check your panhard bar support brace and make sure that the passenger side mount is intact and secure- same with the axle mount. The best panhard bar in the world can't fix rear sway if the problem is elsewhere.

 

Alternate/tangent: I just put a fays2 watts link on my 95 Z28. Went straight from the stock panhard to the watts link and it made a tremendous difference on how the rear end behaved. Down side, it's not cheap ($650) and looks like it would make larger exhaust routing tight; might also interfere with girdle covers on axle.

Back on topic: As both the upper and lower panhards are eliminated with the watts link, when I installed the watts link, I discovered significant deformation of the stock stamped upper bar appx 10" inboard of the drivers side mounting point so you may want to investigate the upper as well. If either of the stamped bars are bent or kinked, it could shift the axle off center slightly.

 

Ok I found the problem/s. I actually took the Rear Control Arms off and found the Poly-bushings to be wornout big time. So what was happeneing is the whole rear axle was shifting causing it to shift in the F/A direction because of the bushings being wornout.FYI there was no wierd bumping or noises. So my next question is where to find replacement bushings for Aftermarket Arms? They're either J&M Racing or BMR with nothing stamped into the metal it's hard to tell. Does anyone know if the BMR's uses a factory bolt? I know the J&M's do.

Also I plan on ordering an adjustable Panhard bar and I'm starting to think it's would close to the same price to just order a package deal since most bushings are near $50. What do you guys think?


Watts links are nice we have been doing ride and handling studies on them at work. They just are too much money for my type of driving or usage of the car. If I was hitting the race tracks them it would be well worth it.

Jeff

 

That's the other 'downside' to poly bushings - they will "cold flow" or otherwise deform permanently and for that reason alone should be considered disposable parts. UMI's Roto-joint control arms might be a better solution in the long run.

Linky


Norm

 

Spohn also has "del-sphere." I went with these as they are a casting versus welded threads, thought they might be stronger.

 

bigJeff_SS, the J&M LCA's w/poly bushings are soft compared to regular poly bushings, and they have a hard poly ball in the center between the two outer bushings.
http://t1.gstatic.com/images?q=tbn:A...G6CR5AbrEAbuE=
If their the J&M bushings, you'll have to get them from J&M hot parts.
If their the BMR LCA's w/regular poly bushings, then part of your handling problems is the fact that regular poly bushings (even new bushings) don't allow the suspension to articulate much at all before binding, which is very counter productive to good handling.

 

Mine weren't like that but they are older control arms they're just two bushings with a steel sleeve. I noticed J&M makes there arms with my bushing setup also. Anyways I decided to buy all new UMI Control Arms and an on car adjustable PHB. I got a package setup from my local shop (EVI). With great pricing and a promise of having them for the weekend why not just buy local. WIN WIN for me.

This is what my rear axle was doing shifting F/A anywhere from a 1/4" to 1/2" so one wheel is moving foward as the other wheel moves backwards. Can you say unwanted active rear steer. LOL


Thanks for all the insight and help everyone.

Jeff