Chip Brown Writes
> I replaced my HM Tourist (Avon)5.25x16 with 165r400 Michelin
> tires/tyres over the weekend. The great big shimmy that resulted
> therefrom is due, I suspect, to one of the tyres/tires not being
> completely seated in its mounting, so I will remove all, re-examine,
> and try again to balance same. Smooth ride is gone because of said
> shimmy but even with the built in vibration but the car corners (with
> 30 lbs of air) a whole lot better. The shimmy going down the Merritt
> Parkway at (any) speed reminded me of a cross-ply versus radial debate
> from years ago.
This should help a number of people I know who want to fit radials to their
16" wheels. We can not source 165r400 tyre here in Australia. Can anyone
suggest a source in the USA or UK?
>
> (There is, by the way, just enough room between the sidewall of the
> tyre/tire in the front and the spring top to get my fingers in there,
> or about 1/3 of an inch. Sisson warns about the whole mess deflecting
> enough to tear up the sidewall: we'll certainly see about that as I
> pull off the wheels this week.)
Sounds about the same as any new Morgan to me. My 1972 4/4 fitted with
165x15 tyres has about the same clearance. I think you would have to be
running very low pressures to cause significant deflection at the top of
the tyre. Interestingly a friend has an MGA with the same sized rims(15 x
5 inch wires) fitted with 185 x 15" tyres. I tried the wheels and tyres on
my car and the gap between the tyre and top of the front spring did not
change significantly. Trouble again is that living in a remote and
underpopulated part of the world 185 x 15" tyres of the correct profile are
no longer available here.
>
> I remember years ago discovering, with a BMW 1600/2 that I had in
> 1967-70 that replacing cross ply tires with radials created a world of
> problems, with the macpherson strut suspension being much more
> sensitive to radial tire imbalances than to cross ply tire imbalances.
> I wondered about that with the Morgan, but decided that this
> suspension didn't really resemble a mac strut at all (actually....) so
> probably wouldn't have these problems.
>
> The question, as I see it is this:Do Morgan owners prefer radial or
> cross ply tires? 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?
The factory has been fitting radial tyres to new cars for upwards to 30
years now. As the front suspension has not changed significantly since HFS
increased the length of the kingpins in 1953 I think any problems
experienced are more likely due to worn components or incorrect assembly
rather than underlying design issues.
Cheers
Steve Moore
Dr. Stephen Moore
CSIRO Tropical Agriculture
Molecular Animal Genetics Centre
Level 3, Gehrmann Laboratories
University of Queensland
St. Lucia, 4072
Australia
ph 61 7 3377 0476
fax 61 7 3377 0480
email Steve.Moore@tag.csiro.au
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