acrace

I'm in the process of putting a "baseline" set up on a C6 Z06 for SCCA Super Stock autocrossing. I'm targeting -2.25 to -2.5 deg camber up front and -1.5 deg camber in the rear, as a starting point.

It seems that my car has about -1 deg camber front and rear right now. I've got three shims under each upper control arm attachment point in the front and one shim under each upper control arm attachment point in the rear.

My question is . . . how much negative camber is achieved "per shim"? Should I yank out all the shims up front and the single shim in the rear?

I also noticed that the cam bolt adjustment in the rear lower control arm is only at the front attachment point. Would adjusting that possibly affect bump steer?

davidfarmer

I can't remember, although I think I took 2 out of each bolt to go from 1deg to 2 deg.....someone else might correct me.

In the rear, the adjustment is just like the C5. Unlike the front, the adjuster is close to the centerline of the axle, so it really doesn't change geometry very much, just straight in/out. Also, the C6Z has shims on the uppers just like the front, so you can adjust there instead of messing with the concentrics.

BEZ06

with David!!

At least for the factory washers that were on my car, each washer was about 1/2 degree.

My street alignment is about -1 degree of camber front and rear.

From the factory I had 4 washers behind each bolt on the dogbone up front, and 2 washers in the rear.

When going from street to my track setup (-2.5 up front and -1.5 in the rear) I removed 3 washers up front and 1 from the rear.

Again, for the thickness of my stock washers, each one is worth about 1/2 degree.

Like David said, the rear upper A-arm on the C6 Z06 is exactly the same as the front - the same dogbone mounts are on the front and rear.

Bob

davidfarmer

just don't strip one...............

mgarfias

Thats why I put studs in before anyone was selling them. Luckily ARP had a size I could use sitting on a shelf left over from some other order.

acrace

Thanks!

autoxer6

FYI
SCCA stock class rules does not allow the removal of the shims. This was protested on a C4 in the past.

acrace

On the C4, the "upper control arm shim" between the control arm and the frame bracket could be removed. But the "control arm upper washer" had to stay in place.

Solofast

On the C4 that was protested the parts removed where the conical spacers on the upper control arms. That has nothing to do with alignment shims or washers.

Any alignment adjustments that are used by the factory or are enumerated in the workshop manual are fair game. Since the amount of upper control arm washers vary from car to car, they are used to adjust the alignment at the factory. Since these are a variable, what or who is to say that the car came with any specific number of shims.

Thus it is acceptable to remove or add shims in this location to achieve any desired alignment as far as the SCCA is concerned. If the workshop manual defined a specific number or a minimum number of shims it would be an issue, but on the C5 and C6, the front dogbone mounts sometimes have washers under them and other cars the come from the factory without washers.

RAFTRACER

I have found the number of "shims" to be pretty consistant between cars .....and I dont believe that I have seen a "stock" car without shims/spacers from the factory. I seem to have alot of these shim things laying around the shop for some reason

Al , better make sure that they call these "shims" instead of "spacers".....alignment adjustment on these cars is all through the eccentrics.

avizandum

Control arm shims are addressed in the service manual in the control arm replacement section, nowhere in the alignment section - and this is copied directly from the manual:

Important: The upper control arm shims will have an effect on the camber and the caster. Make sure to use an equal thickness of shims on both sides of each individual upper control arm bushing.

I think it's a safe interpretation you can have as many shims or lack thereof with no issue.

0C5stein

On the C6 Z06, each washer is 1/8" thick. For every 1/16" of shim removal you gain 0.20 degrees in negative camber. It does effect caster as well (even when you remove equal amount of shims from each bolt) but not significantly. You will need to reset toe if you pull or add shims.

For most of you that do not have a camber caster gauge, I suggest that you get the car aligned for the track leaving 3 or 4 1/16" shims on thos bolts. Then while at the track if you need to adjust camber for better pyro temps, you can add or subtract shims, reset toe, without really screwing up your caster (which would happen if you adjusted the accentrics.

TedDBere

The rule on the C4 was that the "spacers" could not be removed. The shims have always been adjustable. IIRC

dvandentop

mgarfias, do you happen to know the stud size on those??

thanks

Datawiz

I took out 2 of the 4 and can run -2.4.

acrace

Mark:

That's a great suggestion. I would add that a u-shaped "fender" shim (like those that came on the C4s) would be best, so that you wouldn't have to pull the UCA attachment bolt to remove or install a shim. It would make that tweak a lot easier to do at the track.

0C5stein

That is exactly what we do.

BEZ06

Hi Derek

I'm not mgarfias, and I don't know the size of the bolt/stud, but Hardbar makes a stud kit:

http://hardbarusa.com/hardbar/produc...c618f1d7179fef

Bob

davidfarmer

I personally don't swap back and forth....and I find the re-setting of TOE to be difficult for most DIYer's, and they are more likely to damage their street tire from excessive TOE than from a little extra camber.

I thing our car went from -1.2 to -2.2 with 2 washers removed, I put a skinny washer back in to get it down to just under 2.0

C5Stein, how does removing equal shims effect Castor???? I realize any measured Castor might change a bit (since we generally measure it as camber-change), but by definition, Castor is the rearward leaning angle between the upper and lower ball joints, which should not change with a symmetric spacer swap??? Not trying to argue about this one, just curious

0C5stein

Setting toe is pretty easy if you have a friend, some ramps, two 24" straight edges (or toe plates) and two tape measures.

I know that from an engineering standpoint that the caster shouldn't change by taking the same amount of shims from each bolt, because in theory you are only moving the upper ball joint in or out not forward and back. But according to my John Beam laser alignment equipment and 30 years experience setting up race and street suspension, I saw a 0.4 degree caster change with a 1.6 degree change in camber, which tells me that the frame rail mounting points are not absolutely parallel to the center line of the car. Which is why I said "It does effect caster as well (even when you remove equal amount of shims from each bolt) but not significantly." In reality you would never make an adjustment of 1.6 degrees at the track so the minimal caster change is a non issue. Most likely you might make a .2 to .4 degree camber change at the track, so we are only talking about 0.05 to 0.1 degree caster change, with is not worth worrying about.

ps. I disagree on your comment about poor toe adjustment causing more wear on tires than aggressive camber settings based on what we see from aligning over 250 Corvettes each and every year, but that isn't really the point of this post. The C5 and C6s are very sensitive to tire wear with respect to camber adjustments.