Why? Her's why. This rotor cracked at speed on the track at MidOhio. Sounded and felt like someone hit the car with sledge hammer. Fortunately for me, nothing happened other than loosing the rest of the track weekend, but if the crack had been worse, it could have locked up that wheel (right front) as I was hard on the brakes for a fast left hander and could have spun big time. Only rotors that were designed to be drilled should have holes in them.
In this pic, note the markings on the rotor underneath. Each area circled was another crack that was completely through the rotor. And this was after just 8 track days. I switched back to stock Zimmerman rotors and my pedal effort actually was slightly reduced and I had at least the same braking ability if not a bit more. And no brake fade with Motul 600.
