I’m getting pretty tired of getting this car aligned. Had it done earlier this summer and we have perfect smooth roads without potholes here in FL. Went to swap to track tires and found one front tire was corded. Turns out the front right caster and toe were way off. Car got aligned again two days ago. Seemed fine leaving the dealer and then I took a two hour drive the next day to Sebring. Car was pulling slightly to the left and needed slightly right steering to go straight. Two sessions on track with complete curb avoidance and now I’m pulling more dramatically to the left and have to dial in 2-3 deg of clockwise steering. I’m so over this moving alignment garbage on this car.

 

I am nailing curbs and not getting any slippage. Is who ever is doing your alignments tightening the cam bolts to 125 ft lbs as specified by GM? Once you get the alignment set mark the placement of the cams so you can return to the same setting if a cam slips.

You say caster slipped. That usually means camber slips since the two are interdependent on each other. Changing either one will change toe. You can usually make a correction while at the track. Just requires a jack, a couple of jack stands and the correct wrenches. If a cam slips you just turn it back to your marks and camber, caster and toe return to the previous settings.

You can add camber plates to replace the lca cams but that limits most adjustments to the ucas.

Bill

 

Thanks Bill. This time I didn’t have time to mark the eccentrics or check the torque since I picked up the car the night before and had to roll out the next morning. Wish I had though. Last time this happened with the caster change, none of the eccentrics had slipped but but the front right tire had corded with 1,500 street mikes.

Should I be looking at something else like bushings? Or is the guy aligning the car just fudging a printout and giving me a wonky alignment?

 

If the eccentrics don't move the only way to change camber is to remove the bolts holding the ucas and changing the shims behind the dog bones. Equal changes in the number of shims between the front and rear dog bones just change camber. Unequal changes in the number of shims will change camber and caster. Caster alone doesn't cause tire wear since it a measurement of how much the steering axis is leaning either forward or backward not side to side. Camber is how much the tire is leaning to the side and is what can cause tire cording. Lots of negative camber with negative toe in is the worst combination in the case of inside tire wear.

An aggressive track alignment will cause the inside edge of a tire to wear more than the rest of the tire. For instance I have -2.5 deg negative camber in front with +7.4 deg caster and a small amount of toe in and the inside edges of my street tires show a tread depth of 6/32 while all the other places across the tread read 7/32. In the rear I only have -1.7 deg camber with +0.8 deg caster and just about 0 toe. All tread grooves read 7/32 on the rear tires with no inside wear indicated.

Do you have a copy of the alignment setting sheets from the shop that did your alignments? It would be interesting to see the first alignment finishing numbers followed by the second alignment's starting numbers and so forth. That is one way to see of there were changes although small variations can happen just by driving the car off the rack and back on.

Bill

 

My front camber is -2.0. The corded tire’s corner had a shift in toe and became +0.16 while the other side was +0.03.

Now I’ve delaminated a rear Cup 2 after two days (maybe 3.5 hours on track).

Tracking cars is fun but I don’t remember having all these problems with my previous cars. Hopefully just a bad luck streak.

 

Increased toe in on the left (+0.16) would have caused the steering wheel to turn left to center the two front tires so the car would drive in a straight line. You may have had a tie rod that wasn't tightened and turned under pressure permitting the tie rod to turn a flat or two.

Bill

 

I became so annoyed about not getting what I expected that I learned to do my own. I've had a self-aligned car over 160 mph with good stability, so I think I was not too far off what I would have had with a commercial machine, maybe better.

 

Oddly, my 2017 was having a lot of problems slipping itself out of alignment, just by driving on the road for a couple of months. This after a shop run by a bunch of track dogs did the alignment (perfectly, mind you). A couple of months would go by and it would just magically be pulling to the right again; and no, not just following the crown. Toe would be off, camber would be off; it was very odd.

The guys at the shop understand that the cam bolts need to be MFT, too. They hate cam bolts as much as I do and always torqued the snot out of them (breaker bar, etc). But to no avail. I finally had my shop install the camber plates from AMT and the car has been to the track twice so far. Neither that nor the subsequent driving on the road has move the alignment a hair.

 

What kind of tires are you using, I don't think my MPSS had that much tread when new

 

My C6 had the same problem of eccentric bolts slipping all the time, cording tires. I finally put camber plates in and the alignment has held through two sets of tires, problem solved.