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MG Midget and Sprite Technical - Steering rack shim

I think I turfed this out in my ignorance when restoring the car and so have completely non-centering steering.

I'm referring to the packing piece which sits vertically against the crossmember and spaces one of the rack mounts forward (if that makes sense), not the shims which fit around the rack tube.

Looks like they are not available anymore and so I need to make one up - anyone have any idea what thickness they are?

Effectively staggers the rack for some reason and I've been told this might help.
L McInally

I think there are plenty of Spridgets on the road without the shim, but I don't think that is the reason for your steering not self centering.

Have you replaced the rack?...stub-axles?

One or other could be tight. If the stub axles haven't been shimmed properly, it could cause that problem.
Dave O'Neill 2

Before tightening up the rack clamp brackets, you need to attach the steering column, and with the front wheels off the ground, spin the wheel lock to lock a few times. Then do up the clamps. If you do want to add a shim, I think they are around 1/8" thick.
Guy

I had the same problem, not self centring and it turned out to be a (very) slightly bent steering column shaft.
You can still get the shims I got some a while back from Welsh MG and I think B&G may have them as well. IIRC I think they are 3 and 8 thou, I'm still experimenting as there is a rattle from the column over bumps and everything else is tight...

Jeremy
Jeremy 3

Jeremy,
Between 3 and 8 thou sounds very thin to me for these shims. Are we thinking of the same thing?
Guy

You can make the shims from any suitable material, brass, alumium, or steel stock. They can and might have to be used on either side of the rack and in combinations of top or front depending on the rack alignment. Since the steering shaft is fixed and there is no u-joint the shims are used to insure that the shaft is directly in line with the pinion shaft of the rack to prevent binding of the shaft and extra wear on the steering column or rack bushings. With everything properly aligned and the rack disconnected from the steering arms at the wheels you should be able to spin the steering wheel with almost no resistance from lock to lock. If there are tight spots then you need to check the shims until you get it right. You can get a close approximation of how much shim and where it's needed by simply leaving the rack mounting bracket bolts a bit loose and attaching the rack to the steering column. It will move the rack on the loose mountings into a pretty close alignment and you can do some measurments at that point and have a pretty close starting point for how much shim you need.
B Young

3 and 8 thou sounds like the kingpin top shims.
David Smith

given the way the shells were made "back in the day" the shims were added as and when in order to get the rack and column lined up true to each other, to avoid any binding or wear caused by misalignment. Having rebuilt all of the streeing on my midget I found that no shim[s] were needed. They do not help the self -centering mechanism, which comes from the castor angle of the kingpins.
David Cox

Guy, David,

if I'm thinking of the right shims then part number ACA5249 which is 0.003" an part number ACA5275 which is 0.010" (not 0.008" - so my memory's not so good!). Moss stock the former at £2.40(!) but the latter's NLS.These all relate to the early rack which is mine - shims for the late rack all NLS are listed as 0.002",0.004" and 0.010".
The shim for the kingpin is 0.008" which is what you were thinking David and explains my thinking - part number 2A4007 - 56p from Moss. Can't remember if they are interchangable suspect they nay not be as the kingpin shim is I think smaller.

Jeremy
Jeremy 3

Jeremy you are at cross-purposes - the ACA part numbers are shims inside the rack. The OP is asking about 'packing- mounting bracket' which is 'AHA8718 - .79mm - as required'
So .79mm is the answer to the question
or 1/32 inch in old money
:-)
David Smith

David you are quite right I am at cross purposes, sorry chaps AND I've still got steering which needs proper shimming - damn!

Jeremy
Jeremy 3

in the parts book they are 2A6129-30 and 31
.094 (2.38mm), .156 (3.97 mm)and .218 (5.54mm)

Bob
Bob Fisher

This thread was discussed between 08/03/2011 and 27/03/2011

MG Midget and Sprite Technical index

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