So far in the dry, the studded snow tires take 1.5 miles per hour off my average speed which adds about 5 minutes to my 40 minute commute in to work (-450ft total elevation change) and 10 minute to my ride home (+450 ft). Two to three inches of fresh powder cut my average speed in half, for an 80 minute commute to work. And the couple of full-glare ice rides also slowed me by half. The length of time the rest of my combination dry/ice/snow rides seem to correlate with the percentage of dry pavement I encounter. I suppose as I get even more comfortable riding in snow and ice, my average speeds may increase.