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Re: Scalloped tires?!?

On my two first FWD cars I experienced scalloped tyres on the rear.
However, this has not been a problem on any of the 90s or 100s that I
or friends have, despite beaucoup miles and nasty, nasty roads.  All of
these five cars have Goodyear Eagle GA tyres, and both my brother and I
leave the rears in place and replace only the fronts as they wear out.
So the problem should show up here if these tyres have a tendency
toward this problem.  My brother has over 65K of highway miles on
his 1993 100S.

Since it seems to happen only on some cars independent of model, I
propose that the most likely cause is improperly torqued wheel lug nuts
(actually bolts).  On Mercedes this problem manifests itself with
unbelievable shimmy and vibration, and is most noticeable on the front
tyres.  In every case, torquing the bolts to spec eliminated the
problem, which most people thought was alignment or balancing.

Overtightening the bolts will distort the wheel's geometry, and left
unattended will certainly result in scalloping.  Another thing to check
is the rear-wheel-bearing play.  I've seen cars where there is
noticeable play, and while even minimal play will result in a subtle
clunking noise over bumps, it would have to be pretty bad before it
would mess up the tyres.  But it should be checked anyway.

John Greenstreet, Senior Engineer           (jgreenst@motown.ge.com)
Martin Marietta Government Electronic Systems    Moorestown NJ 08057
WPI Class of '75, Temple Class of '94

My new car history:
  1975    1978    1982       1986        1989      1992      1995
   VW ->  Audi -> Audi  -> Mercedes -> Mercedes -> Audi -> Mercedes
Scirocco Fox GTI  4000S    190E 2.3    190E 2.6    100CS     S320

POSSLQ's* new car history:
         1978       1981       1985      1988        1990     1993
       Triumph ->  Toyota ->  Toyota  ->  VW    ->   Audi  -> Audi
       Spitfire    Tercel     Corolla   Jetta GL      80      90S

*POSSLQ = Person of Opposite Sex Sharing Living Quarters
Note: All Audis and Mercedes above were sold to friends or family.