Scalloped tires?!? and parts appetite...

[newbold@banshee.camb.inmet.com (Chris Newbold)]

This week I had the 22.5k service for my '93 90CS. When I brought it in to
the dealer, I complained of vibration and shaking in the steering wheel
and in the front end in general between 55-65MPH. I figured that perhaps
a wheel or two was out of balance.

When I picked the car up, I was told that the problem was scalloped front
tires. Since, they said, balancing could not fix this problem, they rotated
the front tires to the back and balanced the wheels going on the front.

I asked how this could happen at such a low milage; alignment problems,
perhaps? They told me that alignment was not (and would not) be the cause;
more likely uneven pressures or an act of the tire God. Since I'm pretty
careful about pressures (34psi, cold), they said it must just have been
bad luck. The tires are the OEM Goodyear Eagle GAs, 195/65HR15.

Their other comment was that rears tend to scallop more often than
fronts, which actually fits with my experience: the shakes cropped up 
after the tires were rotated previously.

So, what's the deal? Is this really just a random thing, or is it indicative
of some other problem? Driving too hard? :-) Darned annoying, since the
tires still seem to have about half their life left; the shakes gone from
the front now, but I can still feel it from the rear in the seat of my
pants.

Changing the subject... I love this car, but it seems to have a healthy
appetite for parts; something I hope it outgrows before the warrantee and
free service period expire. In 22.5k miles and 1 1/2 years: 1 radiator fan,
1 climate control temp. sensor, 2 steering dampers, 1 rear brake caliper,
1 idle stablizer, 1 rear defroster switch, 1 power steering hose (no trouble
but replaced under factory update program) and now the radio is going flakey 
and the tach is getting sticky.

Hopefully, I'll break everything else that's going to break in the next year
and a half :-)

-Chris