# What is a Euro OEM floating rotor?



## ALEV8 (Oct 3, 2003)

I was checking out www.ufmotorsoprt.com and i noticed the "floating rotors" for sale at like $250 a pair. What is a floating euro rtor and why would I want one? :dunno:


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## mottati (Apr 15, 2003)

*they must be very light.....*



ALEV8 said:


> I was checking out www.ufmotorsoprt.com and i noticed the "floating rotors" for sale at like $250 a pair. What is a floating euro rtor and why would I want one? :dunno:


Actually, i believe with a floating rotor, the rotor and hub are 2 distinct pieces, the rotor is often attatched to the hub with pins, which allows the hub and rotor to expand/contract at different rates, and not transfer brake rotor heat to the wheel hub and bearings.

I've read BMWNA's take on it is the second or third owner may not replace them with a brake job, due to their higher cost, and be stuck with a liability issue if they shatter well beyond their designed lifespan.

Mike
98 528i
00 M5


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## DZeckhausen (Mar 11, 2003)

ALEV8 said:


> I was checking out www.ufmotorsoprt.com and i noticed the "floating rotors" for sale at like $250 a pair. What is a floating euro rtor and why would I want one? :dunno:


Unless you've upgraded your calipers and rotors already to the M5 set-up, you can't use these floating rotors. They are only for the M5, since they are 2mm thicker and 21mm larger diameter. In Europe, the M5 gets these floating rotors, whereas in the USA and Canada, they get the one-piece iron rotors.

You would want them (if you had an M5) because they are several pounds lighter and they don't distort (form a slight cone shape) under track conditions, because they are free to expand and contract without being constrained.

These are not like the Brembo or StopTech floating rotors in which the center aluminum hat can be unbolted from the iron rotor section.









*Brembo rotor bolted to aluminum hat*

When this Euro-rotor wears out, the entire thing gets replaced. It's a mass produced floating rotor (rather clever design, actually) and has a few problems.




























As you can see, after the aluminum is poured into the mold and cooled, forming the hat, the pins are firmly embedded into the hat. However, they slide in and out of the iron rotor (also called "friction ring"). If a pin gets seized, it will not allow the rotor to expand evenly when it gets hot, resulting in a distortion and vibration problems after the brakes warm up. BMW AG actually recommended that folks who had problems with brake vibration should switch to the "American" one-piece rotors.

The grass is always greener on the other side of the pond!


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