Dogbone,
Thanks for sharing your experience and data on the brakes, as well as all of the little details of our kits! Many of our customers don't realize the lengths we go to during the design process. We don't just pull some calipers and discs out of a bin and slap them on a particular car. There is a great deal of thought that goes into them, and the same goes for the design of the individual components. In this case, the front and rear discs for all of our e92 kits were designed hand-in-hand with AP Racing to our specification. They aren't off-the-shelf parts, and they can't be found anywhere else in the world. You won't even find them on the AP Racing website or in their catalog.
Here are some pics I recently posted on Rennlist that show some design work for our 4-wheel brake kit for the 991 GT3:
On the e9x chassis, our 340x28mm disc has proven plenty durable despite their extremely low weight. We frankly don't see that many orders for spare rear discs! They tend to last quite a while, and you can pound out a 24 hour race with them no problem (actually, probably a couple races). A 355x32mm is overkill on this platform, and the only reason we see them is because the manufacturer likely didn't have anything smaller in their arsenal that fit properly. It's either that, or they were just going for bling. For reference, the fastest Le Mans-winning cars in IMSA only use a 355mm rear disc in many cases! Most of these cars are far more abusive on the front brakes compared to the rear, and you don't need a ton of disc mass in the back. It's a great opportunity to shed valuable unsprung weight.
On some of the newer chassis like the F80/F82/F87, C7 vette, Gen. 6 Camaro, etc. the factory parking brakes are bigger, which is why we use a larger 365x30 mm disc. The ID of our 340mm disc won't clear them, or we'd likely use it.
Our rear kit maintains full parking brake capability, and works great with the aluminum hat. It's not designed for rally-style lever yanking while in motion, but it will hold the car in place in the trailer or paddock without issue.
We actually shot a video on our Competition Kit design process. I'm the guy on the right in the video, and you can probably tell that I most definitely geek out over the details.
My friends who have seen our videos are like, "Dude, you get genuinely excited about that stuff, don't you?" Afterwards they probably tell their wives, "That guy has issues." Lol.
