rear end shims

[calgarytrainnut]

Evening all,

Looking to the collective wisdom again as I burned out my rear tires in only 4,000 miles. Old tires that came with the car ('86 US spec 280i) showed no abnormal wear pattern but I hardly put any mileage on those before replacing last year.

So 2 new tires on the rear and had the shop run the car up on the alignment rack. Oy! Specs are in the computer at the corner shop but the tech has no idea how to adjust the rear; thinks it's all fixed (yes, I know better hence my questions below). I also have the alignment specs that are posted on PH. I've seen the pretty picture of the bad news on the alignment computer and this is the info from the printout:

Lt rear camber -2.6 deg, 0.55" toe
Rt rear camber -1.8 deg, 0.00" toe

Lt frt caster 5.4 deg, camber -0.9 deg, toe 0.05"
Rt frt castor 4.6 deg, camber -0.7 deg, toe -0.10"

Someone in the car's past has set it up to dogleg down the road except the right rear is pushing straight ahead. Bye, bye rubber.

Tires have changed from 205 to 195 as that's what's available over here. They are 14's.

On to the nitty gritty. Starting at the rear, castor first. Shims at the discs; 0.25 deg per 0.020" shim (approx). That's easy. The trailing arm shims. What are they (as I think mine are gone http://www.pistonheads.com/gassing/imgs/12.gif)? How thick is each? How far will each shim push the tire out; there must be a ratio of x" moves the toe y"? As the castor shims are always added in first how does that change the toe? What is the diameter of the bolt at the front of the trailing arm that goes through the shims?

Cheers!

Michael

[RCK974X]

Is it the 'trailing arm' suspension type ?

If so, toe-in is adjusted with washers between arm and the large bush at the chassis end. Pretty horrid setup IMHO.

Not sure what the shims do - someone here suggested they help centre the disc in the calipers - that seems to make more sense
than anything to do with suspension, but I don't know for sure....

Anyone else ?

[wild rover]

I would agree with centralising the disc. The shims are also used to the outside of the disc to alter the castor angle.

[calgarytrainnut]

Morning,

Yes, it's trailing arm. The castor shims I understand. I also understand how the shims on the trailing arm work; the questions about details of the shims are at the bottom of my original post. The rest just sets it up.

Cheers!

Michael

[pk500]

You can buy a pack of shims from any jaguar specialist I done both my wedges they drive and handle so much better

[Number 7]

If you mean the shims between the inner end of the driveshaft and the diff, they adjust the wheel camber. As PK500 says, Jag specialists will have them (XJ series).

[calgarytrainnut]

Yep. The castor shims are a piece of cake.

What are the trailing arm shims? Just washers? Anyone know the size? Mine have gone walkabouts before I acquired the car.

And if someone knows the ratio of trailing arm washer thickness to toe movement that's a plus.

Lastly if someone knows the ratio of camber change to toe change as the camber is adjusted that's a plus plus.

Cheers!

Michael

[Tasmin200]

Yes the trailing arm shims are washers, sorry I don't know the size. My tracking is miles out I think. You could do a load of calculations to figure out how much each one changes the tracking but for speed of adjustment (rather than dismantle the whole arm each time) I was going to cut a U section out of some washers and that way you could adust and check the tracking without dismantling the arm. Once it's set dismantle and put the full washers in.

[calgarytrainnut]

I'm trying to avoid the loads of calculations...