rikhek

The thread below is a lengthy discussion focused on rear caster setting and general best "performance" alignment setting for the C7Z chassis. The general consensus of a snap oversteer spin I experienced in my 2015 C7Z is that it was due to improper rear caster setting as delivered from the factory.

https://www.corvetteforum.com/forums...ar-caster.html

I just took my 2017 C7Z in for its 500 mile oil change and alignment. I wanted to see the rear caster setting as shipped from the factory and to have it aligned to my specs. I did not trust the factory delivered alignment.

The factory recommended rear caster setting is 0.0 degrees. The "best" rear caster/performance alignment settings as determined by Mike Levitas/TPC Racing who did extensive testing on his C7Z was +0.8 degrees.

My car was delivered with the right rear set at 0.0 degrees and the left rear at -0.8 degrees. Really disappointing and dangerous that GM built such a good car but does a pitiful job on setting the alignment properly.

Just my luck that the alignment machine my guy used had a broken printer so I don't have the other as delivered factory settings. I do know what the rear caster was as I specifically asked the tech to make note of it.

For those interested I went with the specs in the thread above recommended by Mike/TPC Racing. These were the settings I had on my 2015 which totally transformed the handling and stability of the rear end. No longer twitchy and prone to snap oversteer when driven aggressively. Haven't gotten to drive the 2017 hard yet but I imagine it will be as good as my 2015.

Front - Both Left and Right:

Camber -2.0
Caster 7.1
Toe -0.03 degrees - toe out.

Rear - Both Left and Right

Camber -1.7
Caster +0.8 degrees
Toe -0.03 degrees - toe out. Yes, toe out. Read above thread...

Rick

Al3x_666

And with the new specs how is the tire wear?!

vntgmbk

The factory recommended rear caster setting is 0.0 degrees. The "best" rear caster/performance alignment settings as determined by Mike Levitas/TPC Racing who did extensive testing on his C7Z was +0.8 degrees.

My car was delivered with the right rear set at 0.0 degrees and the left rear at -0.8 degrees. Really disappointing and dangerous that GM built such a good car but does a pitiful job on setting the alignment properly. FWIW, Porsche's come from the factory dead on perfect.

Very disappointing to hear! The alignment before it leaves the factory should be dead on, verified and signed off on. Especially on a flagship model like the Z06 as it probably should be double checked. I wonder how to get feedback for issues like that to the factory line so they can tighten up their QC. With today's high tech and precise alignment equipment, there should be absolutely no reason why every Corvette doesn't leave that factory with a dead on alignment like most other high end autos.
Would be great to get this finding back to the factory QC people if you want to make an attempt.

Mad Dog 24

Rick, Bought a new 17, nice! Lets here what you think about the cooling changes. I've used your same alignment numbers with just a few minor changes and they worked great at WGI. Also set up another 2015 Z the same with success that ran at High Plains. We did use a bit more rear caster I think it was 1 to 1.2. Which we has tested with huge castor numbers over 2.0 with positive results, these cars love lots of rear castor.... on the track.

We had a 2015 Z in the shop a few weeks ago that was a virgin. The rear castor numbers were worse than yours! One side was 0 or a bit positive and the other was - .4 area. That is terrible !!

I was at the factory a few weeks ago and got to ask a few questions and answer a few the "kid" guide didn't know. We were standing near a large glass room with engines in it. He told the group of 15 that's where all the Z06 engines were built. NOT! I corrected him. I think its a sales pitch for perspective buyers to know the Z07 engines were built there by hand and not all.

One important question to me was on alignments. Here's what I was told, at the start of every new shift in the morning they have a "perfect" 2014 Stingray which I saw its night race blue. They drive that car on their two in floor alignment machines and recalibrate the machine to that one cars specs. So, The test dummy car must be off some if many cars are coming of the line incorrect. Or it may be as simple as they need to recalibrate there machines. They have two machines so one may be a bit diff. than the other why my Z was not bad to start with. I noticed walking by the test dummy that the front wheels appeared dead straight ahead and the steering wheel was not centered. My steering wheel was not centered new either, dam test dummy! Really GM's Z06's should use a more aggressive alignment spec than the Stingrays. I've talked to many owners that track there cars stock. They would enjoy the awesome handling much more with a little extra camber front and rear. Camber does not wear out tires, toe does. I use 1.5 to 1.7 camber on the street now 19k miles same Conti's! Their flag ship should be spot on, come on GM.... read this thread! Doesn't surprise me Porsches come spot on.

DRLC5

Good info.

Taimur

So what are the ideal alignment specs for the aggressive street driving? That also helps in straight line acceleration, where camber should be closer to zero.

vntgmbk

It's pretty ridiculous that they are most likely producing and delivering most or all Z06's with bad alignment due to a calibration error. Totally unacceptable. This must somehow get back to the factory so that they can address it. Anybody on here have a contact to get this info back to the factory?

GP1224

"FWIW, Porsche's come from the factory dead on perfect"

Porsche have their own issues. Its been shown many times. But it shouldnt happen in any car period.

http://www.6speedonline.com/forums/991/321196-should-we-get-alignment-newly-delivered-991-a.html

Newton06

Toe out is contra to what GM calls for in it's track alignment...?

Al3x_666

With more caster how will be the wear of my tires?

BEZ06

I don't think rear caster is going to do anything significant to tire wear.

The "positive" caster recommended by a couple of race-prep shops is because they have done an analysis of "toe curve" (the change in toe with compression/rebound of the suspension - usually called bump-steer) and they have found it to be a lot better with positive caster.

Many track hounds will go with slight toe-out up front for better turn-in. But virtually everybody uses toe-in for the rear for better stability during acceleration when tracking-out.

The one shop mentioned by the OP recommends very slight toe-out in the rear. Apparently they have determined that during compression (such as the outside rear wheel during cornering) the rear will toe-in enough to do what most people do with their initial static setup.

Bottom line - improper toe is what will mess up your tires worse than camber. And I don't think changes in caster will cause any appreciable tire wear.

Just MHO - standing by for the alignment experts to chime in!!

.

Mad Dog 24

It should not we use + .05 to +1.0 for the street which means the upper ball joint is leaning back towards the rear of the vehicle. When your suspension compresses the rear toe progressively increases inwards to the center of the vehicle. Normal driving has minimal compression as is the opposite with taking a corner on the track at 100 for 300 feet.

Yes toe out is contra to GM for the rear. As far as I'm concerned a manufacture will always be conservative when giving specs for anything there may be liability involved. We have found and a few others here that starting with minimal out like under .05 degrees per corner seems to work great. At that amount, which we have used, under minimal compression the rear is essentially at 0 toe. What we found is more rear caster creates more toe in through the suspension travel. BTW, I have NEVER experienced a snap out in the rear with these specs.

Search around there has been a lot of discussion on this subject just 3 to 6 months ago.

BaylorCorvette

OP - I'm not surprised AT ALL. I had two track events with my C7 before checking the alignment and the back end was extremely loose, I came from a 2013 ZL1 and thought I made a mistake by trading it in for the C7. Then I had the car aligned including the rear caster and it feels MUCH better now.

Point being, factory alignment is not a sure thing.

sunsalem

ESPECIALLY since it's a safety issue.