Originally Posted by masmole
I'm concerned about the brake clearance wheel requirements for the Stoptechs though. All the posts I've seen mention that a 19" wheel is a necessity with the Stoptech kit. Meanwhile, there's been several posts with pictures as evidence that confirm that the Brembo BBK will at least work with select 18" wheels like Volks, HREs, etc. Is there something about the Stoptech Caliper+Rotor+Hat design that affords less brake clearance for certain 18" wheels compared to the Brembos? If so, this would be a huge deciding factor for some including myself who plan to go with a BBK for track duty, since using an 18" track wheel set up would be more ideal because of the larger variety of R-compound tires that fit available only in 18". This would be unfortunate since the preference towards the Stoptechs because of lower cost and more user-friendliness would be outweighed by the need to go with the obvious benefits of an 18" track wheel set up.
I confirmed with Stoptech today that they will be releasing a 355x35 front kit for the M3 sometime around January. Also, they have seen 18" Volk TE37s clear the 380mm kits before as well. But the 355mm kit is designed to fit in an 18" wheel so this is probably your best option.