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Old 03-01-2007, 11:55 AM   #19
Rob Levinson * UUC Motorwerks
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Join Date: Dec 1969
Location: GA
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My Ride: 7s, M5s, M3s, others
Quote:
Originally Posted by jpr View Post
What exactly does "cast-perforated" mean?
Are the holes cast clear through entire, as a pilot, as a dimple, or something else?
What, if any, machining takes place on the holes after casting?
...

Quote:
Originally Posted by Rob Levinson * UUC Motorwerks View Post
The rotors we use in the big brake kit are genuine BMW Motorsport rotors, which are apparently cast-perforated, not actually drilled.

The difference is that the holes are cast into the rotor, so the metallic grain structure (and therefore the strength) is not compromised as with conventional drilling.
Holes are holes - all the way through. Not dimples.

Normal post-casting cleanup maching takes place, no different than any other rotor... the rotor face, edges, inner and outer hub faces, and casting flash within the holes. When you look at a rotor, every surface that is not rough has been machined.

- Rob
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