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Rear suspension shims


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Does anyone have a rough idea as to the impact in terms of toe in (or out) adding or removing one of the trailing arm shims makes in terms of degrees.

About to check the tracking on the rear of the 4A after changing the bushes and wondered if anyone knew the approximate impact on the geometry to save time and repeated unbolting and bolting of the trailing arm brackets.

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Hi Andy

Sorry I don’t know the answer to the degree question but one thing I found out when doing mine but later done correctly by CTM is that the new shims that you can buy (I assume all) are slightly thinner than the original shims. So that would also have an effect.

Hope this is of some use.

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21 minutes ago, Kevo_6 said:

Hi Andy

Sorry I don’t know the answer to the degree question but one thing I found out when doing mine but later done correctly by CTM is that the new shims that you can buy (I assume all) are slightly thinner than the original shims. So that would also have an effect.

Hope this is of some use.

Depends on where you buy them from, Ive had some that were thicker.

Stuart.

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Hello Andi,

I did this work on my TR6 last week after converting to adjustable brackets.  For the shot I used Gunson's trakrite and removed 2 shims for 2 degree too much toe in.  After that the track was right.  That fit on both the right and left. 

Best regards

Harald

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Hi Andy,

I have just conducted a few simple tests on a trailing arm and spacing out the bushed area (actually the forward outer diameter of the bush lug end)

Very simply If you place a 3/8" thick shim at either the inner or outer bushed lug the  machined surface for the hub moves 4 degrees.

This works out at apprx  1/16" shim = 0.75 degree.

I then repeated the test by starting at 0 shim and increasing by 1/16" shim and this roughly followed the 0.75 degree.

This was approximate as I didn't use the bush centreline but the forward face of the trailing arm (it has a flat surface).

So if you want to move the TA for more toe-in you can remove shims from the outer edge ot add shims to the inner edge. The reverse also applies.

 

Roger

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I adjusted mine from the inherited rear toe in, to neutral (0 degrees) which got rid of the sudden snap from understeer to oversteer in sharp corners.

however at one stage I measured the wheelbase and found one side was a bit longer than the other. Because I was happy with the handling I left it as it was. Dunno what the new owner has done.

Edited by little jim
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31 minutes ago, little jim said:

I adjusted mine from the inherited rear toe in, to neutral (0 degrees) which got rid of the sudden snap from understeer to oversteer in sharp corners.

however at one stage I measured the wheelbase and found one side was a bit longer than the other. Because I was happy with the handling I left it as it was. Dunno what the new owner has done.

Hi Jim,

I'm sure you know the answer but to bring the wheel base equal on both sides add (remove) the same number of shims on the inner and outer attachments.

 

Roger

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Thanks Roger,

think I did as you say, but to get zero toe in I ended up with a different number of shims inside and out on each side. Maybe my welding did a bit of chassis distortion before I strapped it down. Still drove OK. Good that Triumph allowed for shimming, instead of just bolting/fixing the swing arms to the chassis.

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