X-drilled & Slotted Rotors CAN be cut!

[Lil bastard]

It occurs to me that there is one more worry in turning cross-drilled rotors. That is, these rotors have holes which are beveled.

These bevels are a design element that serves three important functions:

They prevent the build-up of pad material at the holes (a source of Brake pulsation).

They also prevent the holes from becoming clogged with friction material from the pad, or mud, dirt, etc.

Finally, and perhaps most important, these bevels act to eliminate, or at least delay, the onset of stress cracks which could lead to rotor failure.

This is a very real concern and probably the biggest reason that cross-drilled rotors are not widely used anymore in racing - racers use slotted discs that better prevent rotor failure and warping. Given Porsche's vast racing experience, I'm a little surprised that they decided to offer X-drilled rather than slotted rotors. I supose that it's because the aftermarket is flooded with x-drilled rotors (they're cheaper to manufacture than slotted ones) and so they enjoy a greater popularity. They also cool slightly better than slotted discs, but I'm not sure that it's a good trade-off vs reliability.

By turning these rotors, you eliminate or reduce this beveling. To do the job correctly, it would be necessary to re-establish this beveling by using a drill press and beveling out each hole in the rotor (on each side). By the time you went to all this trouble, it'd probably less expensive and more expedient to simply replace the rotors.