I lose 2 - 3 mph with studded snow tires, but only about 1 mph with regular tires in cold weather.
A pair of studded snow tires was far cheaper than my ER insurance co-pay would be. It's money well spent. I've been through Buffalo winters, and I know you get plenty of ice on the roads (I didn't bike when I lived there, though).
Last edited by Spld cyclist; 09-05-13 at 08:46 PM.