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Re: Bias Ply Versus Radials- The Morgan Shimmy Is Worse With?

To: ebrown@ms.com
Subject: Re: Bias Ply Versus Radials- The Morgan Shimmy Is Worse With?
From: Jeremy Edwards <jeremy@jmemee.demon.co.uk>
Date: Tue, 10 Jun 1997 23:00:01 +0100
ebrown@ms.com writes
>     The question, as I see it is this:Do Morgan owners prefer radial or 
>     cross ply tires? 

Personally I prefer radials, IMHO cross-plys have a lower level of
adhesion but much more progressive breakaway and for road use they wear
a bit quick. When my car was rebuilt last, after an unplanned excursion
into am 8ft ditch I asked around for the tyre most UK owners would
recommend. I have Goodyear 165 x R15 GT80s as suggested by John Worrall,
(ex Chair of MSCC, co-author of "Original Morgan", Heart of England
Morgans etc.) Compared to the nasty East German cover I had before,
these have been a revalation, softer compound, much more grip and
progressive breakaway when pushing too hard! This is on a slightly
tweaked 4/4- the +8 people I know seem very fussy about tyres, arguing
the merits of Avon, Pirelli and Yokoharmas with equal passion. 

I'm told by a tyre techy that Morgans generally work very well with
modern tyres- the suspension keeps the tyre at right angles to the road,
keeping the maximum contact patch down-(unless the bumps make the wheel
hop off the ground :-))

>     Part 2 of the question:, revisting a question that I 
>     caught the very tail end of just after getting on the eemail list: 
>     once suspension bits are rebuilt and set according to spec, how do 
>     people cope with shimmy?

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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