I have an old Fisher Mt Tam bike I still ride, bought in 1985. I had the fat, knobby tires for years, but I've been away from the rocky trails for a long time, and finally replaced them with Continental Ride Tour tires from Amazon. Don't know if they're that fast, but they are smooth and quiet. I put them on the same rims as the 2 1/4 in knobbies.