DarkMastyr

I am on a stock Z51 suspension C6 with Kumho XS tires, and am noticing that my alignment seems to go out of whack after just one track day. After recently replacing my front right tie rod, I went in to get my toe set, but the caster had changed by over 1 degree since my previous alignment just one month before (to set my front left tie rod right before a day at Thunderhill). Now, just after this previous weekend at Sonoma, my steering wheel is again no longer straight.

Before I go out and start spending a lot of money on a camber kit and a fancy alignment, is this expected for the factory eccentrics? Or should I tell the shop to tighten things down more (or go to a different shop entirely)?

RogerT

If your caster changed, your camber changed also.
Eccentrics should tighten securely to maintain proper adjustment for camber and caster.

Not all alignment technicians are created equal.

Roger T

UstaB-GS549

It's really difficult to torque the eccentric bolts without getting the car off the ground. The torque value is not that high, but you just can't get very good leverage, even standing under the car. If they are tightened to anything less than factory specs they will probably slip. That is why vendors sell camber kits.

I did my front camber 5 years ago and it has never changed.

froggy47

Insist your tech use a torque wrench or find one that will.

93Rubie

Torque the fasteners and it should be fine.

I had my rear camber move around on my C4. When I did the alignment MYSELF, I torqued the rear camber eccentrics to spec. (186 ft-lbs) with a torque wrench. A PITA to be sure, but after a season of auto-x on street tires it has not moved. I marked them with paint, so I could see if they did move.

Make sure they are actually aligning the car. A lot of alignments are a Toe and Go. No messing with the caster or camber. Lazy and dishonest techs do this all the time. There are ways to fudge the numbers so it is in "spec."

Find a reputable shop or do it yourself.

TKOGTO

I have had the exact same experience. Stock suspension, Kumho XS tires, freshly aligned to Pfadt track use with street tire specs, car felt great. One track day and the alignment was shot to hell. I got the Pfadt camber kit installed and JOC stage 1 sways and shocks and had it realigned. It was still a mess. Turned out the rear cradle bolts had loosened. The whole rear end shifted leaving the rear tires pointing in the same direction. Toe in on one side, toe out on the other. Maybe that's your issue.
Going back to the track Saturday. Planning to bring the car back to alignment shop to compare the rear toe after vs. where we set it. If they loosened up again, will talk to Pfadt to see if there is an alternative.

DarkMastyr

Just took it back to the shop this morning. Everything seemed to be mostly ok except for the LF camber/caster. It had slipped from -1.3/8.0 to -1.6/7.2, causing the steering wheel to be crooked. A week before, the same LF corner had slipped from -1.3/8.3 to -1.5/7.4. Front toe seems to be slipping a tiny bit as well. I told them to tighten the bolts to spec. We'll see how it holds up.

Shaka

No matter how much you tighten the bolt, there is insufficient friction area on the eccentrics to retain alignment on certain impact loads. There are vendors here that can fix it. Perhaps they will chime in.
$125 grand car with cheap stuff like this is not acceptable. Lets hope this design is revised on the C7.

Solofast

You need to mark the excentrics with a stripe of nail polish so that if it slips you can just put them back where they were and be on your way in minutes....

Also, I firmly believe that addding a strip of nail polish acts a super locktite, since after I do that I've never had one slip.... musta been the stripe....

Pfadt Racing

These headaches are exactly why we designed our Corvette Camber kit. By moving to a series of plates and shims and eliminating the factory eccentric bolt you can lock your alignment in place and no longer have to worry about what your alignment is doing on track.

If you're not running a camber kit the best advise we can give is to make absolutely sure that the bolts are torqued to the factory specification after every alignment. This isn't a situation where "mechanic tight" will reliably get the job done. Make sure it's done right otherwise it's a matter of time before you see your alignment change on track.

Vettechris996

Did you check their work? Cheap insurance if you track the car...

Sharpie also works perfect for marking the eccentrics to see if they have moved. I put a camber kit in my car after having them slip on race tires. At least if you know they are torqued properly and you're still having them slip that a camber kit might be a good/worthwhile solution.

DarkMastyr

Marking the eccentrics is a good idea. I will do that. I will also see about checking the torque.

mountainbiker2

I run 335 Hoosiers A6's and never had the eccentrics move. You have to torque to spec. It's really that simple. Do not take there word for it, watch them.

Steve A.

taken19

I know you were talking about a C4, but that seems a bit high. C6 eccentric bolts only get torqued to 107 ft-lbs if I remember correctly.

To the OP...

Either way, the camber plates will eliminate the potential for that happening on you again and cost about as much as 3 alignments. It may be worth considering.

Shaka

Another thing. The bushes bind with eccentrics and hysteresis is noticeable and you also alter caster and toe when you only want to change camber. The shocks can't be tuned properly either. Eccentrics belong on cheap production cars with very complient bushings. Shame on Chevy.
If the cam bolt hole is not a aligned with bushing and the outer lower ball joint, it will align itself under a sufficient impact load especially if it is 90' off plane. Slicks will do it every time resulting in a sudden toe out on the outside rear and a dramatic uncontrollible spin. Pay me now or pay me later. If you have eccentrics on your race car, you are plain dumb. Shim blocks must be installed on both sides of the lower A arm or makes steel lower A arm with Heims. A good machine shop can fix your stock car.

mikeCsix

Here's another vote for the pfadt camber plates. Last year, first time out my right rear camber adjuster cut loose with a bang. Didn't know what it was and thought felt like a tire bead blew out. Fortunately I did not lose control of the car and when I hit the next straight the wheel was way off, nearly 90 degrees. The incident ended my track day.

When I replaced my '08 Z-51 with a '12 GS, before my first track day I replaced the eccentrics with pfadt camber plates. It is an expensive and laborious install but at least I don't have to worry about it anymore.

93Rubie

That spec. was per 93 Factory Service Manual (FSM).

froggy47

On a c5 107 is one spec on the rear iirc the other rear eccentric is like 120 and fronts like 130 ish.

David Farmer's site has the specs.

larryfs

186 ft-lbs on camber eccentrics is a typo in the C4 manual. I busted rear caliper bracket bolts on the 1996 C4 due to typo's in the manual.

In fact, my son busted wheel studs because he thought I said 180 ft-lbs, when I said 100 ft-lbs.

Shaka

Right. Pay me now or pay me later. How much to avoid a certain crash.