Turning lca eccentric for positive caster
 

The dealer checked and recorded (took picture) of rear caster on '19 Z06. The reading, not very visible, is -0.4 and is within factory spec. The rear wheels showed identical caster readings. I occasionally track the car and read about the potential for snap oversteer and want to adjust the lca eccentric to get caster positive. Questions: Does each tic mark on the eccentric bolt correspond to a specific change in caster degree? And, if I am interested in going from neg to positive caster, looking from the rear of vehicle, which way does the eccentric bolt rotate? I cannot remember if changing caster affects camber or toe, so in reality, I will likely take it back and have the dealer realign everything. Thought it was worth a CF ask.
https://cimg6.ibsrv.net/gimg/www.cor...a453230512.jpg
-0.4

The marks don't really mean anything except as a reference. Rear caster setting is very touchy to adjust. Small movements of the lca cams make big swings in rear caster while also swinging camber.

You may get more caster movement using the front cam and more camber movement using the rear cam. Once set you can see large swings just tightening the cam bolts down to the 125 ft lb torque setting. The reason you see large swings in the number is because the measurement is so small with a spec of 0.0 degrees plus or minus 0.8 degrees. Getting the DSC -1.7 degrees of rear camber along with the +0.7 degrees of rear caster makes it hard to set toe since you run into a lack of adjustment range on the toe link cam. I could not get any toe in adjustment at all and the least amount of toe out I could get was about 1/32.

Bill

In order to solve that range issue (that Bill mentioned), you can remove all the washers behind the UCA mounts at the rear, and replace them with a thin washer instead (I've used 1/64" shim from Harbor Freight). GM recommends leaving one washer behind the arms, so I left the shims in case it's a mounting surface issue.

This allows you to get an additional 0.3-0.4 degrees of camber for free.

Bill, thank you. I do recall reading about the adjustable toe links. Not sure if the dealer would touch those and that might force a DIY route. Appreciate the help.:thumbs:

X25, great idea. I'll swap out the uca washers with a thinner one and then schedule appt. with dealer. Appreciate the pro tip. :thumbs:

Is it better to do the caster align with weight in the driver area?? How long does it usually take to do the rears?

It definitely will help. After all, this car never drives itself, and a driver (weight) on the seat makes it more accurate. And yes, it impacts all alignment numbers in my experience (though none too significantly).