Originally Posted by Carbonic
On my cool-down lap at a track session on Saturday I suffered catastrophic brake fade (pedal went to the floor), brake warning light and DSC warning light activated (stock calipers / pads). I nursed the car back to the pits to cool down, and after 20 minutes I noted that one of the stick-on wheeel weights had 'melted' off the rim, and the white BMW lettering on all 4 calipers had turned yellow. After about 1 hour I was able to drive (gently) home, the warning lights cleared and brake functionality gradually returned. I will now strip the calipers at the next opportunity to check for piston damage.
Be careful when you do your inspection of the caliper.
There's no need to go any further than removing the caliper, and removing the pads to do a visual inspection.
Fade can almost be expected during extended track use with OEM pads and OEM fluid.
You essentially hit MOT of the pads, and boiled the fluid at the same time.
Fluid Fade = Soft Pedal
Pad fade = Loss of friction
Soft Pedal & Loss of Friction = Fluid and Pad Fade together.
Your next track event you're going to want to put in a high performance fluid with a higher wet and dry boiling point.
IE: Motul RBF600, ATE Super Blue, Brembo Sport 500, etc...
You'll also want to seek a pad that is more suited to track situations with a wider temperature range. there's not a lot of choice out there yet for your caliper but between Hawk and CarboTech I'm sure you can find something that is more suited for track use. You may find that it will be neccesary to have 1 set of street pads and a dedicated set of track pads. If you can find something that has friction at ambient temperatures for both street and track use, also make sure to ask if it is friendly on the disc.
Braided lines are another way to ensure a firmer pedal feel and will give you better feedback so you will be more aware of what your pads and discs are doing while you're on the track. Normally you will have early warning signs before "catastrophic brake fade". The lines may provide you with more of that predictable feel.