[Olle]

I had my car at a shop for alignment last year, and I asked them to add some positive caster to it. When I got it back, they said that 1 degree was all they could get out of it. I haven't measured the difference in shims front-to-rear, but my calibrated eyeballs say about +1/8" on the rear bolts.

Looking at the amount of shims, there's another good 1/8"-3/16" (for a total difference of 1/4" - 3/8" if you move shims between rear and front bolts) that could be used for further adjustment, and there's plenty of thread length left. Now I'm wondering:

-Is there a max allowed difference in shims between the front and the rear bolts? I would assume that you can't cock the shaft too much?

-Can the shaft be bolted straight to the frame (ie: shim the rear bolt only) in order to get max caster?

I'm almost done with a complete front end overhaul and it will be time for alignment again pretty soon, so I want to be more educated on this before I do it.

And for those who are wondering why I aligned it before the overhaul... I didn't know how sloppy it was until they started doing the first alignment, so I told them to get it as close as possible. This still doesn't explain why they didn't use the full adjustment range.

 

[Jack Action]

From my '69 Pontiac Service Manual, it says «Shim as required. Min. one shim at each bolt.» Nothing about a max allowed difference in shims. But we also have to assume you still have the original bolt length.

 

[Olle]

Yes, the bolts are original and there's plenty of thread left.

 

[Aaron]

If you dont have any adjustment left in the factory shaft, look into a offset shaft.

Maybe you can find a circle track or road race alignment man in you area to take a look at what you have on the car right now.

 

[Schurkey]

Keep in mind that you're using the same shims to adjust caster as you are to adjust camber.

Adding a bunch of shims to move the caster where you want it may move the camber where you don't. Camber is a tire-wearing adjustment, caster isn't. I sacrifice caster to get proper camber.

 

[thunderstruck507]

So if I have installed aftermarket upper control arms which have 4* caster built into them and I put the same shims back in the arm (getting aligned tomorrow) could I have way too much caster and that be what is causing the tire to rub the rear of the inner fender at full lock?

If not I might need to try raising the front of the car a little.

 

[Olle]

Keep in mind that you're using the same shims to adjust caster as you are to adjust camber.

Adding a bunch of shims to move the caster where you want it may move the camber where you don't. Camber is a tire-wearing adjustment, caster isn't. I sacrifice caster to get proper camber.

Yep, I'm aware of that. Actually, the marching orders i gave to the shop was to get as much caster as possible, while maintaining camber. It still seems like they didn't get all the caster you can get out of it.

So again: Any ideas about how much difference you can have in the shims?

 

[Olle]

Maybe you can find a circle track or road race alignment man in you area to take a look at what you have on the car right now.

That would probably be a good idea. The guys in the alignment shop freaked out when they saw the tall upper ball joints, they were fixin' to pull the cotter pins "to tighten them up" and I had to tell them to either leave them the hell alone or take the car off the lift and abort the operation. I tried to explain what tall ball joints are for, but they didn't get it. They even went to the shop owner to make sure that they were't liable for the ball joints falling off the car... :sad:

I'm not sure if I can find a mechanic with race track experience, but I will definitely find another alignment shop.

 

[Aaron]

I think you need to list all the parts you have on the car.

If you get the front end decent and research what you need and take in some specs. Any alignment shop can put that in there. However, if you bring in something unworkable, then they cant help you.

 

[Olle]

I think you need to list all the parts you have on the car.

If you get the front end decent and research what you need and take in some specs. Any alignment shop can put that in there. However, if you bring in something unworkable, then they cant help you.

Just an OEM front suspension with tall upper ball joints, that's all. Nothing unworkable at all. I suspect that this shop doesn't really know how to work on these cars, that's why I want to figure out what the limitations are so I'm better armed when I go to the next one.