Alignment / Caster Question w/pic
Thread Starter
Drifting
Joined: May 2008
Posts: 1,647
Likes: 5
From: Roseville CA
Alignment / Caster Question w/pic
I got my 71 BB aligned yesterday for the first time and the caster is out of spec in the front. I didn't have my glasses on when I picked it up, so I couldn't read the measurements and they didn't explain or point this out. Which kind of pisses me off now.
Anywho, I looked at the shims and there's one 1/16, maybe 1/8 shim, at each of the four upper adjustments. Couldn't they have dialed in the caster by adding more negative camber? In my mind, they should have added shims to the rear adjuster, thereby moving the upper ball joint rearward, and also slightly inward. Adding caster and also negative camber. It's possible the camber would go out of spec since the front shim adjustments are nearly bottomed out. I'm not sure what's worse, not enough caster or too much negative camber.
I have a 2009 Z06 setup for autocross and it has -1.7 degrees front camber and it drives fine.
This also makes me think there is some cradle sag.
Anywho, I looked at the shims and there's one 1/16, maybe 1/8 shim, at each of the four upper adjustments. Couldn't they have dialed in the caster by adding more negative camber? In my mind, they should have added shims to the rear adjuster, thereby moving the upper ball joint rearward, and also slightly inward. Adding caster and also negative camber. It's possible the camber would go out of spec since the front shim adjustments are nearly bottomed out. I'm not sure what's worse, not enough caster or too much negative camber.
I have a 2009 Z06 setup for autocross and it has -1.7 degrees front camber and it drives fine.
This also makes me think there is some cradle sag.
Drifting
Joined: Jun 2007
Posts: 1,404
Likes: 1
From: Ansonia/NYC CT
Your Z06 has newer wheels and tires, though. It also likely has a much better steering system. All of which affect the way a car behaves, especially when you run negative camber. As for cradle sag...I feel you on that.
Racer
Joined: Mar 2006
Posts: 493
Likes: 2
From: Dunellen New Jersey
Adjusting the caster just to reach specs may affect something else.If you adjust one side the car will pull.Its all relative to the car.The frame could be slightly tweeked,You could have a worn part or 2,Negative camber will give you good handling but will hurt tire wear.Its all how you want the car.Racing?Street to go to a car show?
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
I'm thinking something else is wrong. With equal shims front and rear you should not have zero caster. Have you checked the control arm bushings?
But yes, you can add shims in the rear to get more caster and some neg camber.
Your current alignment is likely to be unstable on the highway.
But yes, you can add shims in the rear to get more caster and some neg camber.
Your current alignment is likely to be unstable on the highway.
Pro
Joined: Nov 2007
Posts: 721
Likes: 105
From: hernando fl
get all the caster you can get up to 3.5 degrees a little negative camber up to about -.5 should be ok. with what you are describing shim wise you probably won't be able to get very close to that though...........a little negative camber with radial tires is not too much of a problem. get too far past -.5 and tire wear is a problem
i agree your current setup is very likely to be unstable at highway speeds mostly because of no caster
i agree your current setup is very likely to be unstable at highway speeds mostly because of no caster
Thread Starter
Drifting
Joined: May 2008
Posts: 1,647
Likes: 5
From: Roseville CA
I'm going to talk to the shop and see if they can get the caster back in spec. I agree, I don't like the idea of that little castor. I'd rather live with some negative camber if that's what it takes. It's not driven that much, so tire wear won't really be an issue. I do want it to track nice and straight and not have any darting tendencies.
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Don't worry about tire wear @ -0.5 camber. Most likely you will notice reduced wear compared to the stock spec. When I had stock specs my outside edge wore first. Neg camber made it wear evenly.
You may also want to look at getting a spreader bar to push the cradle apart.
You may also want to look at getting a spreader bar to push the cradle apart.
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
I agree: You don't have enough caster, and you could easily increase it by increasing your negative camber. This should improve your handling, although your alignment shop might consider it to be out of spec that way. I can't help thinking they were too lazy to spend a little more time to get it right.
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Melting Slicks
Joined: Nov 2010
Posts: 3,363
Likes: 32
From: Bowtie, Pennsyltucky
St. Jude Donor '13-'14-'15,'21
I apologize if I'm "hijacking" but can anyone recommend a book or other reference material to learn all I can about alignment changes and the effects on handling as described above? Thanks
Melting Slicks
Joined: Aug 2008
Posts: 2,200
Likes: 3
From: Lehigh county Pennsylvania
If all you need is more positive caster and you don't want to install a bunch of shims to get it, there is another way: slot the upper control arm shaft holes 1/4" to the front...that will move each upper ball joint to the rear of the lower ball joints increasing your positive caster ~2.5 degrees.
I did it to mine and with shims got a total of 4.1 degrees needed for my Steeroids power rack.
This was explained by member norvalwilhelm in the summer of '07.
I did it to mine and with shims got a total of 4.1 degrees needed for my Steeroids power rack.
This was explained by member norvalwilhelm in the summer of '07.
Last edited by 69 Chevy; Jun 20, 2011 at 10:17 AM.
