My two cents. I'm back on bimmerpost after a long hiatus. Had an E90 M3 that I tracked heavily and really enjoyed. (Emphasis on heavy
-- that heavy beast went through tires and brakes like nobody's business!) I then moved on to a 991 Carrera S, and now a GT4 for track use. Pretty certain I'll try to pick up an M2C as a daily driver.
The OEM E9X M3 brakes were completely inadequate for track use. I switched early on to a Stoptech BBK front and rear. They felt great, were robust, and their removable bridge design made for quick pad changes without removing the calipers.
On the 991S, I kept the stock calipers but upgraded the rotors to two-piece, slotted GiroDiscs. Also got Pagid RS19 pads. Based on reports of others, the GiroDiscs lasted me much longer than the stock rotors would have, and when it came time to replace them, I saved money by retaining the GiroDisc center hats and just replacing the outer friction rings. Brilliant.
Now on the GT4, I've also kept the stock calipers but upgraded the rotors to 2-piece AP J-hooks from the team at Essex. They've been fantastic. Lasted a good amount of time on track with PFC11 pads, and again, the 2-piece design allows for just switching out the outer friction rings while retaining the center hats. Much cheaper than replacing the entire OEM rotor assembly each time. And with the J-hook slotted design, no worries about the OEM cross-drilled holes forming cracks over time. Why Porsche insists on continuing with cross-drilled brake rotors on their GT cars is beyond me. It speaks volumes that their customer race cars come with slotted rotors and not cross-drilled.
So, in summary, strong recommendation for AP Racing and the guys at Essex. The rotor design is great, and the ability to change pads without removing the rotors is a huge plus.
