TKOGTO

I have had a problem with my 2010 GS AG pulling to the left for some time and can't figure it out. Looking for ideas. So far, we've tried:
1. new alignment - worked initially but one day on track and alignment was shot
2. rear sub-frame - while doing 2nd alignment, noticed rear sub-frame was loose and pointing to the left relative to the frame. Thought this was it, it wasn't. Lock-tited the bolts and even welded sub-frame to frame - no go even with anothor alignment
3. brakes - used infrared thermometer on the rotors to see if one was sticking. No appreciable difference left to right. If anything, right temps were slightly higher

Also, tires are new as well as sways and shocks (JOC Stage 1). Pulling occurred before and after tires + JOC.

Any ideas?

Thanks

Screamin Z

The GS is a steel frame car right? Isnt the rear sub frame aluminum? Cant weld those two together.

Id check the rear sub frame again.

Bill Dearborn

. Is the car pulling or is it dog walking? Dog walking is an issue with improper thrust angle and usually means you have to have the steering wheel turned in a certain direction to to go straight. Although the wheel is turned it isn't pulling. You can center the steering wheel position by adjusting front toe and drive down the road without much pull even though the car is actually going down the road sideways. The rear sub frame on my Z is off to the left by about a tenth of an inch but it doesn't cause any pulling. A good alignment guy should be able to make rear toe adjustments that set the thrust angle close to zero and thus pretty much eliminate and tendency to dog walk.

Caster can cause a pulling in one direction or the other since the steering will pull in the direction of the front wheel that has less positive caster.

Camber can cause pulling with the car pulling in the direction of the wheel with the most positive camber.

Since caster and camber are interrelated I usually find if I set my camber it is very hard to get exactly equal settings from side to side and the side with the most negative camber usually has less positive caster.

I wouldn't get too upset by small differences in the alignment from side to side. The alignment specs have wide tolerances and small differences from side to side are usually something that you need to live with as it can take hours to equalize them if it is even possible to make them equal. Some mechanics will adjust caster differently from one side to the other to compensate for the pulling you get when driving on a crowned road.

You could also have issues with tire pull, tire pressure, or brake drag.

Bill

SouthernSon

Pulling while floating throttle? accelerating? decelerating? Last time I had a problem was getting alignment on same equipment three times. Tried another shop and problem was fixed. Time before that was bad shock in one rear corner, under acceleration pulled to left.

RogerT

It is possible that you have a bad tire on the side that is pulling.

Hope this helps.

Roger T

froggy47

see above

I don't know any alignment shop or other shop that would weld a sub frame to the frame as a fix for anything, you may just need a new shop. Do they do race alignments on many vettes? Or any alignments on vettes?

davidfarmer

I agree with all above...plus you can't weld the subframe to the frame!??

Anyway, unless there is damage or excessive wear, it is mostly likely a bad tire or bad castor. Swap/rotate tires and see if it changes. If that doesn't help, I'd make absolutely certainty that the castor is even side-to-side. If that doesn't help, you have a mechanical problem somewhere.....

TKOGTO

Bill - dog walking (crabbing) is exactly what it is doing. I need to turn the steering wheel ~ 10 degrees to the right to keep the car from drifting then darting left. Forearms are exhausted after a day @ the track.

I have had this condition on 3 different sets of tires with no difference so we have eliminated that so far.

TKOGTO

I notice it most when driving on the highway. I tend to lighten my grip, sometimes steering with 1 hand. It's @ these times it is very noticeable. I don't notice it at all accelerating or braking.

TKOGTO

Condition is the same on 3 different sets of tires, one old, one ready for the scrap heap and the run flats I use after the track season is over. these last tires have < 3k miles on them. Thanks though.

TKOGTO

Froggy

1. re: "alignment shot", by this I mean, the car started crabbing again. It was aligned to the Pfadt track use with street tires specs in April. Car felt perfect after this alignment. One day @ Lime Rock and it was crabbing again. Same thing happened @ the end of the season. Aligned, it's fine, one day @ LRP it's crabbing again. It was after this 2nd "failed" alignment, the shop welded an L bracket off the chassis rail to keep the sub-frame from moving. What I stated in the OP re: welding the frame to the sub-frame was not correct as noted above.

2. Yes, same alignment shop. My confidence level is high with the shop. I watched the last alignment so I know it was done to the Pfadt specs.

3. The tranny had work to fix a leaking seal in June but I don't know if that required loosening the sub-frame. Either way the problem existed before then and no other work was done on the rear.

TKOGTO

Yep, my mistake on the welding. What the shop did was weld an L bracket off the chassis rail to keep the sub-frame from moving after they got it where it needed to be.

Same issue on 3 different sets of tires. I don't have the alignment spec sheet in front of me but I am sure the castor was very close to 8.5 degrees on both sides.

froggy47

Is the alignment shop torquing the bolts to the spec (125-150 varies by the bolt)?

Maybe get a camber kit which will NOT slip & let alignment chg.

redtopz

Re-set your rear toe and make sure rear thrust is symmetrical. Use camber plates instead of the eccentric bolts. That should solve your problem.

AU N EGL

Street alignment to factory OEM specs is much different then an alignment by a race shop

TKOGTO

My guess is yes. I was watching them work on it when they discovered the loose bolts. Tech went back to the office to check the torque spec before tightening. I will however confirm this.

Camber kit was put in @ time JOC sways and shocks were added. I will hear back later today whether alignment changed again and if so how much. When I spoke to them before I brought it back, tech suggested it was a brake hanging up because he assumed the camber kit and L bracket should have kept alignment in place.

froggy47

Well if you already have camber kit/plates that's a whole new kettle of fish.

I'm running out of ideas.

Sub frame movement loosening is not something I have heard of happening much. My front sub frame was loosened to fix a front engine cover leak & we marked the before/after alignment & it does have locator pins which limit the adjustment/movement to a couple of mm I believe.

Tightened back up to a big torque spec (I forget) and it's never moved/loosened since (couple years).

yooper

Had similar problem with rear suspension of CTSV.

First thing I would do is put a wrench on every bolt under the car. If you find one loose, replace the nut if it threads on by hand.

The rear lower control arm nut came loose after an alignment. Tech at local dealership put his kick azz Ingersol Rand gazillion ft lb impact gun on high and let it rattle. I had him take the nut off and replace with new. He tightened the lock right out of the locking nut. Tighten with torque wrench only!

Same thing with axle nuts, do not reuse if you can thread on by hand.

TKOGTO

[QUOTE=froggy47;1582567927]Well if you already have camber kit/plates that's a whole new kettle of fish.

I'm running out of ideas.
:ack

Understood. Appreciate the effort.

TKOGTO

Will try this.

I started marking everything I could easily get to a few months back so I could check periodically if anything loosened. I did not check that each was properly torqued to begin with. That was more trouble than I was willing to take on. I did check the front end after my last track day and nothing had moved. However I only did the rear about 2 weeks ago so I could have marked something that was not torqued to spec.

What is strange is the 1st 2 alignments corrected the issue only to have it return after 1 track day. The last alignment which included the L bracket I mentioned above did not improve the crabbing at all.