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The Morgan Shimmy

To: ebrown@ms.com
Subject: The Morgan Shimmy
From: Jeremy Edwards <jeremy@jmemee.demon.co.uk>
Date: Fri, 10 Oct 1997 22:03:05 +0100
I'm sorry to see that your shimmy is back. I append my original post
below as I think it gives a suitable order and I notice that various
people give similar advice.

As adjusting the damper blades can be a bit of a fiddle, it often gets
ignored and as Dave Vodden points out some people don't think it to be
much of a factor, however it the easy things are sorted, it's probably
the next cheapest to do.

To adjust the blades, back off the clamping bolts to the shims and look
at the edge of the shims to make sure they haven't worn to a blade edge.
If they have, replace them and the blade itself. Push the shims against
the blades and tighten then to a sliding fit, so the blade can be bent
in and out from between the shims. At the end of the process, you should
not be able to pull the damper blade for and aft along the car, although
you should be able to bend the shimmed end out and back. (Daft
description, but I cannot think of a better one).

Chassis         ________________________________

                SSSBBBBBBSSSSS  (a parallel sliding fit)
                SSSBBBBBBSSSSS
                   BBBBBB
                   BBBBBB
                   BBBBBB
                Stub Axle assembly                      

I apologise for the world's worst ASCII diagram!

With everything set up properly, there won't be any, but tracking down
the one thing that is doing it on any particular car can be a pain. With
mine it was tyres out of round, (flats on the tyres from lack of use),
and worn damper blade shims. Colin Musgrove in his book "Moggy" makes a
few helpful suggestions, but to condense half a chapter it came to:-

        (i)     Adjust the damper blade shims to stop the damper moving
                fore and aft along the car, but not so tight as the 
                damper can't move in and out.
        (ii)    If you have any difficulty with this, replace the damper 
                blades and shims with new- they can wear quite badly.
        (iii)   Have the front wheels balanced properly- splined wire 
                wheels require the correct hub adapter or else!
        (iv)    Check the tracking.
        (v)     Make sure the cross frame bolts are tight, the king pins  
                greased and the brakes not dragging.

After that little lot, make sure the wheels and tyres are round- not as
daft as it sounds- buckled wheels after being kerbed, tyres out of round
after standing too long, cord failure in the tyre all can happen. Then
check the steering gear- duff track rod end perhaps, freeplay in the
drop link?

After that little lot, black magic and prayer!

Personally, IMO most bad shimmy is the product of a number of the above
factors.

Happy Hunting- It took me a month.
-- 
Jeremy Edwards
1972 Morgan 4/4 2 str
1970 Opel GT
Melton Mowbray, England

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