From digest.v9.n1395 Thu Mar 2 22:14:18 2000
From: "Dan, Marilyn, Anathea & Phillip Patzer" <bmrfamly_at_nwlink.com>
Date: Thu, 2 Mar 2000 04:41:03 -0700
Subject: E28 shimmy
"SHIMMY" is caused by irregularities in geometry, or friction. They are
allowed by looseness in the suspension.
Geometric irregularities would include bent or out of balance wheels,
irregular treadwear, or warped rotors. The time of occurance of the shimmy
tells us what the source of it might be.
Friction irregularities would include "annealed" rotors. Each time the
wheel stops rolling, 15% of the rotor is still baking beneath the hot pads,
while the rest is being cooled. This results in a non-homogeneous metal
surface, which may still be smooth, but will be "grabby".
The E28 front suspension has 14 ball-joints, 5 major bushings, 2 minor
bushings, and two strut tower mounts. That's a lot for possible sources of
looseness on 14 year old parts.
If the car is an automatic, I've found a high metalic content pad works
better to reduce the "shimmy".
Dan Patzer the CyberWrench from BIMMERS ONLY Seattle's exclusive BMW hobby
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