18's for Winter Tires?

[PK8]

I have an E92 335i on order w/Sport Package (18 inch wheels), and I'm already thinking about winter tires (my car won't be here until August, so I've got to do something to pass the time!). I'd like to get a second set of wheels to avoid the remounting issues, but I would rather buy new summer wheels than winter wheels, and use the stock 18's for winter. My concern is going with 18's during the winter. Would I be giving up too much by way of traction, etc., vs. 16's (not even sure if 16's will fit) or 17's? BTW, I live in South Dakota, so I will be dealing with snow and ice for more than just a few days a year. Thanks in advance for replying!

[Titania]

You're always better off going with the narrowest tire possible for winter use. I don't have a 335, but I'm fairly sure that 16"s won't clear the brakes.

[Gran Turismo]

+1
Sport package sounds like a staggered setup with especially wide rear tires, the latter being the worst option regarding traction on snow and ice.
For a 'safe' winter setup, you rather should stick to the narrowest non-staggered tire/wheel dimensions available from the factory for your model. That would be 4x 225/45R17 for a 335i, as a bonus the smaller tire dimensions will also be a little cheaper.

[PK8]

Thanks, guys. Not the answer I was hoping for, but it makes since to me.