I have a new 335i xdrive, I'm presuming that is also what you have. First of all havn't you noticed how rough your car is riding up there in sub 20 degree weather, that's because the run flats turn into rock in cold weather. During the recent warmup we had here in northern illinois, my car rode much smoother than it did when we were having that bitter cold at the end of december. Also my dealers head service wrench told me the 3 series likes to eat tires. I'm planning on changing to winter tires and new wheels from tirerack for the next winter. I also have 17's, and I think 18's or 19's will look nice, but you will trade that for ride quality. And with the roads up there you could even bust a wheel. I hope my two cents worth helps.