Interesting. TireRack recommends the 225/50/17 as an alternate winter spec:
http://www.tirerack.com/snow/WinterP...06&autoModClar=
For the 330i with SP, they recommend 225/45/17 or 205/50/17
http://www.tirerack.com/snow/WinterP...04&autoModClar=
Didn't think you could do 16s on the 330i, though....Hmmm.