I have a 2008 535i with the sports package and currently have installed 245/40-18's on the front and 275/35-18's on the rear. I live in Chicago and need to put on snow tires and rims and would like some recommendations on rim and tire sizes and brands. Can I go to smaller diameter? Like a 17"? HELP!

 

Of course you can go 17s - they will definitely fit - you just need to make sure you get the right back spacing.