[spidertri]

I'm running F30 fronts (caliper and rotor), 328i rear calipers on the stock 128i rotor, 135i MC. I've beat the heck out of them this year and just swapped back to my street pads for the winter. I don't really have a plan right now to upgrade the rears again.

I've previously run floating calipers with brass bushings and the swap to the F30 caliper was an immediate increase in pedal feel, it is considerably better than the floating style fronts.

Rotors are 348 x 30 for the 335i fronts and 340 x 30 for the F30 fronts. In terms of heat capacity, the larger 335i rotor will have more, but at the same time your braking technique greatly impacts how much heat you put into the rotor.

Cooling is probably a wash because you need to remove the backing plates, or cut away as much as possible to even begin letting air get to the center of the rotor more effectively and these are OEM rotors so

I think either set up is going to be plenty for only doing a couple track days per year. The bias shifts forward about the same amount for the 128i performance brakes, 335i fronts, or F30 fronts. Make sure to code in the +spbr option and the DSC module will handle the bias shift.