A set of average "ebay-grade" rotors: wimpy pattern, lousy cadmium coating.
Porsche 911S crossdrilled rotors, OE on most of their cars. Made by ATE, excellent quality, superior pattern with full-spectrum coverage.
Masking & Coating Application
Chamfering & Cleaning
Stock OE Rotor
CAUTION ABOUT BUYING EBAY ROTORS
Masking & Coating
RETAIL DRILLED ROTOR MANUFACTURE:
We've been making custom crossdrilled brake rotors since the fall of 1997...we also deal with about 4 or 5 major west coast distributors. We have personally spoken with factory reps from almost all your major manufacturers: ATE, Brembo, Girling, Zimmerman, BBS (Becker Bremscheiben), Bradi (which is a lower-quality Brembo off-brand), OP and a few other unknowns.
HERE IS YOUR BIG KEY: there is no such animal as "factory crossdrilled rotors". The casting process (with current technology) just flat-out doesn't allow for it. In other words, the rotors don’t just “roll off the foundry line” with the holes somehow already “cast into the metal”. They have to be milled into the steel AFTER being cast.
Also, even at the industry-level, crossdrilling is a slow and tedious process---even with a fully-automated CNC machine doing the work. (this is largely due to the number of holes per rotor.)
There are only a few companies out there that even sell factory-replacement "performance rotors" under their own name; one is Zimmerman, with their "sport crossdrilled" rotors. Even they, however, are having them milled at a separate facility on a contracted basis. (And the Zimmerman ones are pretty wimpy, if you get a close look at them; not even close to the patterns we do.) Even Porsche factory rotors--usually made by ATE or BBS, depending on the model and year, (for the 911 twin turbo, for example) that come crossdrilled when you buy the car, are being done out-of-house by a Porsche-subcontractor.
Pretty much every company that you see out there that sells crossdrilled rotors, is doing them in almost the exact same manner: they purchase the blank rotors from a supplier, and a subcontracted machine shop is doing the milling and chamfering. They then sell them under their own name. And of course the way they make money on them is by purchasing them at lower cost, and raising the price to make a profit.