caster shim question

[backyardbill]

I'm almost ready to put my suspension back together. When I took this mess apart, there were not any shims to set the caster. So, I want to get it back together right. Have a look at (Img 10-4.1):

http://www.glocktech.net/fiat/restorati ... t%2010.htm

I have a new box of shims that were meant for vintage GM products. The "c" area is a little too small to slip over the pivot bar shaft. I was just going to grind out enough of the shim to fit. What do you think?

[kmead]

I don't believe that is how you adjust caster on a Fiat. I may be wrong but I believe you would adjust caster by varying how many shims are between the front or back threaded rod of the crossmember and the pivot spindle (the object you have in your image). This requires a careful dance between caster and camber in placing/choosing the shims.

The distance between the bushes of the A arm are not variable (at least not intentionally). I don't believe there is enough thread or space on the pivot spindle to move the arm forwards or back to change caster.

Caster is primarily set by the base structure of the car during assembly: the mounts for the lower crossmember relative to the weldment of the upper a arm mount to the body and the geometry of the weldment of the crossmember.

[manoa matt]

Bill, caster and camber I also get mixed up. Regardless, don't install any shims between the pivot bolt and the crossmember. Drive carefully to where you are getting your alignment. The alignment mechanic will have the needed shims. I'd stay away from chain stores/franchised places, think 18 year olds that never seen a Fiat before. The factory specs call for loading the car with 2 people and 140 pounds of luggage.

I have my guy set my alignment specs with me sitting in the car. 99.9% of the driving I do is with only me in the car so to set it with 2 people plus 140# is not feasible since it would cause abnormal tire wear if I'm the only one in the car most of the time.

[backyardbill]

Your right. After reading your followup, I had to go back and again study the explanation on caster and camber in the Fiat Spider Service Manual, Chapter 44, pages 44-14 thru 44-15.

At first, it seemed logical to shift the lower control arm forward or backward along the pivot bar to achieve the desired caster angle. But now I see that by putting shims on the pivot bar would interfere with the proper clamping of the inner sleeve of the bushing to the lower control arm and the bar itself.

Yes, by removing shims behind the front (of car) pivot bar (to crossmember) bolt, and adding the shims behind the rear bolt, the front of the control arm would be moved inward, thereby moving lower ball joint forward, which would create more positive caster.

Thanks for the help.

[kmead]

When I read your initial post and looked at the pictures I really had to scratch my head because your approach does make sense. I was then trying to think about how many shims you would need to actually make a change and just how much fun I had in changing the rubber bushes and that you couldn't actually move the arm along the shaft because of the thread length and I had never seen shims on that part. Which is not to suggest I have seen everything.

Angling the lower a arm can create much more forward/backward displacement with minimal shims.

I recall that many GM cars move either the lower or upper (usually upper) arm forwards or back to adjust caster.

Glad to help.

[backyardbill]

Followup. I finally finished the front end job, and did the alignment. Have a look.

http://www.glocktech.net/fiat/restorati ... t%2010.htm

I won't be able to road test the car until Sunday.

Do you think that the number of shims that I used to get it within factory specs are too many?

Any and all comments and criticisms on my methods are welcome !

Thanks to all for your help.

[engineerted]

Looks good bill That is exactly how I do it for my race car. Did you use a little oil between the floor tiles to make them slide? The shim count looks good also, but I would advise re-torque the nuts after your first outing. Some how those nuts and shims like to move a little bit. I double nut my bolts but I also run with extra long bolts in the cross member.

Ted

[backyardbill]

Thanks. Do you ever use locktite on these threads?