Originally Posted by djpathfinder

1) You must keep overall diameter (O.D.) the same as OEM +/-0.6" no matter what size rims you get. O.D. of OEM 19" setup is 26.5-26.8" otherwise your speedometer will be out and your ride height/ground clearance will change.

2) For winter, you want a tire with either a slightly larger aspect ratio (ie. sidewall) or equivalent to your OEMs...therefore, 18" or 19" wheels, to allow for more tire and thus better winter grip. No need to go with 20" rims.

In terms of section width, go no wider than OEM (245/275). In fact it's OK to go with slightly narrower width tires, because they will handle icy roads better...think of maneuvering on ice with snow shoes vs. ice skates.