I'll tag into this thread, because I'm having the same problem.
Brief history: I've had problems with brake fade at the track. So I switched up to Performance Friction pads that are rated for full-on track use, and now I can't get the system to bleed to where I feel comfortable with it. I'm running the Performance Friction pads on slotted UUC rotors (should be "compatible"?). I ended up replacing the master cylinder last weekend and putting another 4L of fluid through it, and it's still only mediocre-feeling. The rationale for replacing the MC was that, after significant bleeding effort, I was getting a pedal that was mushy for the first push, less mushy for the second, and kind of OK by the third push. So even for street driving, I felt like I needed to push on the pedal twice to get enough stopping power to be useful.
My bleeding process is to use the pressure bleeder and the ScanTool from AutoEnginuity. I kick off the "ABS Air Bleed" process on the scan tool, then open the bleed valve and dump fluid into a jug while the computer cycles the brake system. I was doing each corner twice before moving on to the next corner, going RR/LR/RF/LF as per tradition. Then I went around and did the computer-aided bleed on each corner, but before going to the next, I'd punch the brake pedal HARD about 8-10 times (or until my leg gets tired). Punch fast, release slow, then go check the pressure and fluid level in the pressure bleeder.
After putting 4 liters of fluid through the system, it's safe to drive, but I feel like the pedal is going too far down, and it's just ... it lacks that solid feel. If I'm going to come into Turn One at 120 and hold my brake point until the last second, I'd like to feel Really Good about my brakes. Having done a bunch of brakes on a bunch of cars, I'm really feeling crummy about the brakes on this one. I mean, it's a BMW, right? It should have awesome brakes, right?
It occurred to me today that I haven't bled the clutch yet -- is that the One Thing that I'm missing? Or is there some bleeding trick I'm not doing that's causing me problems? Any hints or ideas?
Thanks,
Dan