1. Were you the one who tried to fit the new rotors? If so, did you squeeze (retract) the caliper pistons fully into the caliper? Caliper, especially if it has new pads, won't fit back over the rotor if the pistons aren't fully retracted.
2. Turning the rotors (you called it grinding) can provide temporary relief, but the real problem lies just aft of the steering wheel. It's you, or more specifically, your braking habits. Background: brake shimmy has plagued bimmers since the 1980s. The cause is USUALLY NOT warped rotors. Depending on your driving and braking style, a microscopic amount of pad material can transfer unevenly to the rotor, changing the local friction coefficient. Can especially happen if you hard stop with hot brakes and then hold the pedal down. I'll skip the how, for now.
Good new is that there is a long-known likely solution: Get yourself some uncrowded highway space. Run the car pretty quick( 50 to 80 mph or so) and make sure no one is right behind you. Make a hard almost-stop - don't come to a complete stop, just bring it down quickly to 5 mph or so. Repeat maybe five times. The brakes should get GOOD AND HOT, you may be able to smell them, that would confirm they're nice and hot. This procedure CAN scrub the rotors sufficiently to evenly distribute the minute amount of pad material transferred to different areas of the rotor. Depending on your enthusiasm for this practice, it works better for some than others. Think about your braking style and what you can do to change it.
Try this (at your own risk) are report back.
Charlie
Your mission, should you decide to accept it, is to add value to these threads, either by pictures or by descriptions, so the next person with the same or similar problem stands on your shoulders.
Member
Posting Permissions
Reply With Quote
Bookmarks