Quote:
Originally Posted by bigjae1976
I learned something today.
I frequently check my rotors. I have the E46 M3 DD rotors on my 330. There are a bunch of tiny surface cracks which I've read are from the expansion of the rotor under heat.
I do carefully check the rotor for cracks which extend to the edge and where it mounts to the hat before and after I go to the track.
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First off, remember that these are different rotors than stock. The floating BMW factory rotors float on pins, not ears like this, and the failure mode would look very differently.
It's "normal" to have small surface cracks emanating from the holes in a drilled rotor, but if you ever have cracks all the way through the rotor, stop use of them immediately. Sometimes it's hard to see, but try shining a flashlight through the vents.
Definitely for those of you running non stock rotors, checking the areas that James mentioned is critical. Any cracks in those areas should be time to shitcan the rotor.
Also, what I hate about tracking a street car is that I almost inevitably get judder in my pedal from running a different street compound... makes it hard to notice a new vibration, but if you do, it's definitely time to pull off and closely inspect things.
I don't think you're going to see a stock rotor fail in the same way, although people have cracked stock rotors before...