Hi
I put Continental TS830P 225/45/R18 RFTs on my 400m (same size/offset as yours). There are only two approved BMW winter tyres in those sizes - the other being a Pirelli SottoZero II.
Pics are here:
http://www.f30post.com/forums/showpo...&postcount=224 http://www.f30post.com/forums/showpo...&postcount=231