Noticed on my new front rotors
 

Just had the front brakes replaced on my 2000S and noticed that the drilled holes in the rotors are slightly beveled whereas the old rear rotors are drilled but not beveled. I don't recall that the old fronts were either. Same on your S's? Part number starts with 996...

Its a little hard to tell but my 2001 S has slightly beveled holes in the rotors.

The bevel will be less visible as it gets worn off.

Fronts
https://lh5.googleusercontent.com/-l...ront092912.JPG

Rears
https://lh6.googleusercontent.com/-2...rear092912.JPG

One goal of the slight beveling is to reduce the likelihood (or maybe delay) the formation of cracks that emanate from the drilled holes. It is surprising that the OEM rotors didn't have this feature.

Aha! That must be it! Thanks!

I didn't stay in a Holiday Inn Express last night :D but I believe " drilled " rotors are manufactured two different ways. One is when the rotor is cast the holes are part of the casting process. These are more costly to make and less prone to cracking and are not chamfered. The second way is after the rotors are cast they are then machined/drilled. Less costly but more prone to cracking so part of the drilling process also bevels the edge of the holes.

I believe that cast in hole theory is a common myth. There was actually a bounty offered on corner-carvers.com to anyone who could provide evidence of a rotor produced this way.

There certainly are photos of rotors where the hole clearly shows signs of casting. Most seem to be high-end OEM. Not sure about aftermarket.

To the op, a good question is what brand rotors did you buy?

I'd love to see it. On that other site, no one could source any conclusive evidence.