Alignment Shims
Thread Starter
Racer
Joined: Nov 2013
Posts: 254
Likes: 6
From: Houston Texas
Alignment Shims
While doing an alignment on my C5Z, I ran out of caster adjustment on the driver side. After inspecting, nothing appears bent, or otherwise damaged.
I googled around and found some people use shims on the front of the upper control arm to increase caster. Are there specific shims to be used, or are universal alignment shims acceptable? I tried to find specific shims for our cars, but came up with nothing.
Is there a company that makes such a thing?
I googled around and found some people use shims on the front of the upper control arm to increase caster. Are there specific shims to be used, or are universal alignment shims acceptable? I tried to find specific shims for our cars, but came up with nothing.
Is there a company that makes such a thing?
Melting Slicks
Joined: Nov 2008
Posts: 2,938
Likes: 65
From: Rochester Hills MI
If you look where the upper control arms attach to the frame there are some washers under the attachment points. This is how they do the caster alignment from the factory. You may be able to remove or switch some of the washers around in order to get the caster you desire, but you may also need additional washers.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Make sure that they are NON ferrous so they wont corrode/deterorite. Most alignment shims are SS. Ive uses SS washers on other non C5 cars and you can get them from Homedepot or LOWES
Melting Slicks
Joined: Jul 2004
Posts: 3,092
Likes: 120
From: orlando florida
St. Jude Donor '15
It begs the question
What do you mean by ran out of caster adjustment?
What numbers are you trying to achieve?
Post the camber and caster numbers you had.
Signed - the alignment guy
What do you mean by ran out of caster adjustment?
What numbers are you trying to achieve?
Post the camber and caster numbers you had.
Signed - the alignment guy
Thread Starter
Racer
Joined: Nov 2013
Posts: 254
Likes: 6
From: Houston Texas
Thanks gentlemen, I'll source some generic shims.
mrr23, I mean that I cannot achieve the desired numbers. The car is lowered a fair amount. How greatly that affects camber (which affects range of caster adjustment, I'd assume), on these cars? I can't say. I'm not a C5 expert by anymeans.
For the time being I'm using basic Hunter specs. It's just a weekend toy, roll race car, so the goal is to keep camber close to stock, or even a little less mild. I'm at -.46 camber both sides, 7.0 caster on the front right and maxed out caster on the left front at 4.92.
I'd really like to get it up to 6.5 or so. Our roads around here have a pretty nasty crown, and I have decent luck with a bit of cross caster offset for cars at work to compensate for the pull/drift of the road crown.
mrr23, I mean that I cannot achieve the desired numbers. The car is lowered a fair amount. How greatly that affects camber (which affects range of caster adjustment, I'd assume), on these cars? I can't say. I'm not a C5 expert by anymeans.
For the time being I'm using basic Hunter specs. It's just a weekend toy, roll race car, so the goal is to keep camber close to stock, or even a little less mild. I'm at -.46 camber both sides, 7.0 caster on the front right and maxed out caster on the left front at 4.92.
I'd really like to get it up to 6.5 or so. Our roads around here have a pretty nasty crown, and I have decent luck with a bit of cross caster offset for cars at work to compensate for the pull/drift of the road crown.
Melting Slicks
Joined: Jul 2004
Posts: 3,092
Likes: 120
From: orlando florida
St. Jude Donor '15
something is wrong if you can get 7.0 on the right and only 5.0 on the left. next time you are on the rack, use the faster caster option to get SAI and IA readings. also check setback (its in the other measurements button) for the front. this will help to determine what's going on.
did you measure ride height at all four corners? i just use a tape measure from ground to top of fenderwell.
yes you need right at 0.30 higher caster on the right versus left to offset road crown. i do caster measurements with me in the car. much more accurate because the car doesn't drive by itself. 16 years of experience here owning my own alignment shop.
if you want to call and discuss the next time you have it on the rack, PM me and i'll give you my number to call.
did you measure ride height at all four corners? i just use a tape measure from ground to top of fenderwell.
yes you need right at 0.30 higher caster on the right versus left to offset road crown. i do caster measurements with me in the car. much more accurate because the car doesn't drive by itself. 16 years of experience here owning my own alignment shop.
if you want to call and discuss the next time you have it on the rack, PM me and i'll give you my number to call.
Last edited by mrr23; Jul 29, 2016 at 05:49 PM.
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Thread Starter
Racer
Joined: Nov 2013
Posts: 254
Likes: 6
From: Houston Texas
I've had both cradles out (as well as both upper arms unbolted from the frame), so it's possible I reinstalled the shims that were there already, in the incorrect spots.
Thanks gentlemen, I'll give you a shout if I can't get it dialed in with reasonable shimming.
Thanks gentlemen, I'll give you a shout if I can't get it dialed in with reasonable shimming.
Team Owner
Joined: May 2001
Posts: 87,334
Likes: 1,589
From: Western NY
On older cars, that were aligned by adjusting the upper a-arm, this would be done by adding more shims to the front mounting bolt of the a-arm. Since C-5s adjust caster/camber at the lower a-arm, this would be achieved by adjusting the rear eccentric on the lower a-arm, moving the a-arm outward, which "tilts" the lower ball joint, with respect to the upper ball joint.
However, if you've used up all of the adjustment at the bottom, and can only get 7* of caster, you may have to shim the upper arm, to get you where you need to be. Add a shim(s) to the front mounting bolt, and see if that will do the trick.
Melting Slicks
Joined: Jul 2004
Posts: 3,092
Likes: 120
From: orlando florida
St. Jude Donor '15
You should be able to get it without shims. Max caster would be front bolt all the way inward and rear bolt all the way outward.
Last edited by mrr23; Jul 30, 2016 at 09:27 AM.
Melting Slicks
Joined: Aug 2004
Posts: 3,003
Likes: 89
From: Indy IN
He may not be getting the caster if his upper front control arms are bent..
What happens is that the upper control arms deform from braking forces. You can see this visually if the rear upper control arm joint seems to be pulling off of the bushing. Check the thread below for pictures.
It's most noticeable in cars that are tracked on serious tires like Hoosiers but I'm sure it could happen to a street car too if the braking is aggressive at times.
Given that these cars are now getting old and the bushings can deteriorate over time that is what it could be. Or it could be that the previous owner tracked the car and that is what caused the issue.. Anyway, this is most likely the cause of the lost caster.. Fortunately the fix is easy, as described in the thread, you can flip the rear bushing in the arm and it will be good to go.
Here's a thread on the subject in the autocross and roadracing page in the general section, along with pictures of how the arm pulls off of the bushings.
https://www.corvetteforum.com/forums...s-options.html
What happens is that the upper control arms deform from braking forces. You can see this visually if the rear upper control arm joint seems to be pulling off of the bushing. Check the thread below for pictures.
It's most noticeable in cars that are tracked on serious tires like Hoosiers but I'm sure it could happen to a street car too if the braking is aggressive at times.
Given that these cars are now getting old and the bushings can deteriorate over time that is what it could be. Or it could be that the previous owner tracked the car and that is what caused the issue.. Anyway, this is most likely the cause of the lost caster.. Fortunately the fix is easy, as described in the thread, you can flip the rear bushing in the arm and it will be good to go.
Here's a thread on the subject in the autocross and roadracing page in the general section, along with pictures of how the arm pulls off of the bushings.
https://www.corvetteforum.com/forums...s-options.html
Last edited by Solofast; Jul 30, 2016 at 03:00 PM.
Racer
Joined: Jun 2013
Posts: 256
Likes: 3
From: West Texas
You haven't hit anything have you? If you hit a curb or something it's possible you tweaked the lower control arm on the left side and shoved it back a bit causing low caster.
Last edited by Boss75; Jul 31, 2016 at 11:33 AM.