I don't gear down my fixies (49x17 and 42x15) in the winter..the same gear ratios work just as well for me regardless of the temperature. Even in the winter, most days are still dry, so for me there's no real point in gearing down most of the time. However, I do resort to riding my SSMTB (Flip 34x15; Flop 34x17) on really snowy and/or windy days.