: THANKS !!!

The floating rotor is a rotor that is not solid from the hub through the disk. Typically the hub section has splines like on a bicycle wheel the actual hat is a separate piece that is then attached to the splines. The floating rotor disapates heat MUCH faster than a solid rotor, for the obvious reason that air can flow comepletly through the rotor. BMW has chosen to NOT bring this rotor into the States because of legal concerns. Apparantly the rotor hat can shear off the splines if the rotor is worn down severely. We are talking 100k + on a set of rotors. However, BMW feels that Americans do not take good enough care of their cars, and they do not want to fight the hassle.

Also of interest here. When we mention the floating rotors available for the E31, we are also talking about a ///M front caliper that was made by ATE that must be used if you go to the floating rotor. This caliper is a four piston caliper that works quite nicely. You must also change the hubs and the backing plates, as the HUGE new rotors will not fit the existing baking plates. New hubs are also needed if you wnat to utilize the pin setup on the new rotors. The difference in braking is awesome.

Just as a side note, when I took delivery of my M5 in Europe, I noticed significant brake fade at high speeds with the vented but one piece US rotors. I had them changed out for the Euro rotors and have had no such issues since.

Stephen