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Alignment degrees to shim thicknesses

09-08-2008, 12:39 AM
Ok, I'm doing an alignment to my 85 s10 pickup. I've got my angles and now I'm at a loss. Its a shim alignment so its easy to do but the thicknesses of my shims are throwning me off. Angles are as follows:
Caster - +2 degrees
Camber - +.8 degrees

What I have
Caster - LF = -1 degree (off by 3 degrees)
FR = -1.5 degree (off by 3.5 degrees)
Camber - LF = -.75 degree (off by 1.55 degrees)
RF = -1 degree (off by 1.8 degrees)
My questions are 1. What is the conversion from degrees to inches? and 2. Is 1 degree is .2 inches (or 1/5) and 1/16 inch shim is .3 degrees? (this doesn't add up) And no guys, nothing on my truck is bent, it was aligned by a moron when I got my tires (I didn't have a bubble gauge when it was done.)

09-08-2008, 09:16 AM
Can you shoot a picture of your upper a-arm? Either side will do, this would tell me which way the arm has to move. This is for the camber only, caster behaves the same regardless of a-arm location.

How are you getting your caster measurements, do you have a magnetic spindle gage and turn tables? You really have to turn the wheel in 20 degrees, zero out the caster reading, turn it out 20 degrees and you read the gage.

When I used to do alignments for a living, I would figure out what I had to move and do them in one shot, per side.

For a beginner, I would work with the camber first. The a-arm has to go outward to make yours more positive. Work both shim packs equally. I would go with an 1/8" on the right side, leave the left alone for now or go with a 1/32" or 1/16" shim. Most alignments I've done were accomplished with the bigger shim sizes.

For your caster, it has to go more positive (upper balljoint tips to the rear of the car). You can change the caster and not disturb the camber by moving shims back and forth from the rear to the front of the arm and vice versa. This only works on symmetrical arms! More than likely you have to take shims from the rear and add them to the front.

If you have a "pull", you can get it out by moving the shims back and forth in the a-arm. It will always pull to the "leading" balljoint, the most negative caster. For instance, if it pulls to the right, take a 1/16" shim out of the rear of the arm and add it to the front.

There is no real correlation between degrees and movement that I know of, all cars do not react the same way due to ride height and condition of springs, etc. Every alignment is unique.


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