Quote:
Originally Posted by Tiago@VRSF
Generally shaking while braking is caused from brake pad deposits caked onto the rotor from high speed braking on a soft/oem pad. Most shops only change $10 per rotor to "turn" them which essentially means they take off a small amount of material off the face of the rotor and that fixes most issues.
The shake will be significantly worse if you have any worn suspension bushings which in that case you'd need to replace the bushings first and if the problem persists, you'd look at the rotors.
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I wouldn't recommend turning any BMW rotors, and BMW specifically states that you shall not.
But you're damn right about the bushings. This is the exact symptom of a bad Thrust Arm bushing, or Upper control arm bushing on the front. Pad deposits are the reason the brakes shudder, but the worn bushings magnify this significantly.
Avoid getting the brakes hot and coming to a stop with your foot firmly on the pedal. With an automatic, this is not easily done. It glues a microscopically thin layer of pad material to the hot rotor, and you can even see the imprint. This is somewhat normal, but just try to avoid doing it. The bad thrust arm bushings - or possibly worn balljoints or tie rods if your car has a lot of miles on it - are 99% certain the cause.
FYI - the E9x M3 thrust arm bushings are a direct press-in fitment. The thrust arms are identical, only the bushings are different between the M and non-M.