tire size differences

[motorcritter at webtv.net]

the problem with running different sized tires on an all-wheel drive
vehicle (like an quattro) is that your expensive gizmos that sort out
the torque to the various wheels get really confused by the variances in
rotational rates at each wheel. then those components tend to quit
working and/or self destruct. the only way to insure that the tires are
all the same size is to run the same brand and model tire at each wheel.
although the sizes themselves are standardized, the diameters of
different manufacturers tires can vary within certain parameters, and
this variation can be fatal to the aforementioned components. i hate to
be the bearer of bad tidings regarding this sort of failure to a
customer, but then again, it's not my car, and i didn't do it to it. i
will fix it, though, and it is not cheap. the tire education is included
at no extra charge. marc

that which does not kill me makes me stronger-f. nietzsche   after all
this i am still alive-m. burkhardt