I run track events at Sebring with the 240. There are a lot of variables, such as brake pad material, disk size and ducted air.
I've put a temp gun on my rotors, not the hubs, and the temp was in the high 300's. This was after driving down the back stretch and through the paddock area, so my guess is the temps were much higher, probably 600-700 degrees. I would say the hubs see at least 300 degrees when I am on the track.