Once the initial excitement of having a fixed caliper brake system from the factory wears off, I believe that many M4 owners will find their OE brake system inadequate for serious track use. The OE BMW hardware does not compare to what is provided by the aftermarket, even when the supplier and manufacturer is the same (Brembo).
I believe one contributing factor is pad swept area. I did some quick analysis in this thread:
http://f80.bimmerpost.com/forums/sho....php?t=1081905
Pad areas when compared to a Brembo GT kit are as follows (StopTech numbers would be similar)
M3/M4 OEM front: 71cm²
M3/M4 OEM rear: 40cm²
Brembo GT front: 95cm²
Brembo GT rear: 62cm²
