Frequently Asked Questions - BMW M coupe Brake System
If I have rust on the piston, is the piston bad, screwed up, leaking?
Part of the piston is exposed to the elements, so it's going to look bad over time. The working part of the piston is behind the dust boot and seals. What will happen over time is the dust boot will start to fail and let dirt in, which can lead to the seal leaking. Or overtime due to high heat caused my many track events the seals will leak.
How tight should I torque the bolts that hold the caliper to the strut?
If you plan to serviced your rotors several times a year and at every track event you remove your calipers to installed race pads, hand tighten the pins and then a ¼ turn more or so (a small red spot in the palm of the hand). You want to be able to remove the pins again without getting out any special tools or hammer.
Is the Euro rotor a true "floating" or "multi-piece" rotor?
The Euro rotor has the benefits of a "floating" or "multi-piece" rotor when it comes to heat transfer, the hub and rotor are made up of two different metals. The Euro rotor is not assembled like a true "floating" or "multi-piece" rotor they use nuts and bolts to hold the rotor to the hat. The Euro rotor is manufactured with pins that point towards the center of the hub, the hub is then cast around the pins.
I noticed that in inside the Euro rotors were shaved on one side, is that for balancing?
During the manufacture of rotors, most are machined and spin balanced. The machining process removes the high sides on the rotor surface and balancing is done by removing material off the edges of the rotor or by adding small loops of wire to the inside, you can sometimes see this by looking down into the vanes of the rotor.