knobby tires are ok for winter, but I'm sure I would have saved myself a lot of pain for a few days in highschool had I known there were studded bike tires available. At that time I had one of those departmentstore CCM MTBs. maybe 2~3 days of ice during the winter, but a butt load of snow to go through. Rarely ices over, but a lot of compacted or unplowed snow.