Rear Brake Disc Vane Rotation Direction

[m3f_Type H]

Please help me out, this may sound like a silly question but it's hard to tell once the old rotors are taken off *before* the garage make a note of it.


I went to check out the rotors installed in other M3s & I have seen them installed in both right & wrong ways which I can't differentiate. Should:


(A) Outer leading edge swept backward (taking fresh air from inner vent holes & exiting at outer vanes)?


(B) Outer leading edge swept forward (scooping fresh air from outer vent holes & exiting at inner vents)?


So much for fluid dynamics, many thanks!

[m3f_M3 Imola GT]

Answer "A". I had to double check my part numbers as I thought it was the other way round!