[pavproch]

I´d been thru that.... having been immersed in web forum for quite a time, I came to following:

e89´s share the same master brake cylinder (34336786755) with e9x cars. I presume that master cylinder has been designed/optimised for single piston calipers (both front and rear), so althoung implementing some alternate BBK (4 or 6 pistons) might be (mechanically) PnP and would bring you some extra large rotors wit it, to get the best of of it you should play with its controlling SW.... what does not attract me a bit... that is why I simply swapped OEM 330ix front brakes (rotors 330x24mm) to OEM 335ix ones (348x30mm) + calipers, caliper carriers, pads, clips, sensor, obviously. No need to playing with the software, though.

And it brakes like hell now.... (I am referring to the other car of mine - 3er- see my signature)

But... speaking of Z4, I will not go for these larger rotors (35is), because that would mean adding some 5 kgs per wheel ...