I just replaced my rear tire Friday night. I replaced a Bontrager Racelite hardcase with a Specialized Armadillo. They are similar tires, both have aramid liners. I felt like I was dragging an anchor on my training ride Sat. AM.
Two weeks ago I did a 42 mile loop and averaged 19.1 MPH. Last week the same loop I averaged 20.0 MPH. Both rides on the old tire. This week I rode the same loop plus a hill section. On the normal loop my average dropped to 18.5 MPH for the 42 miles. Down to 17.7 MPH for the total 52 miles. The temperature yesterday was 39 so I had shoe covers, a jacket and gloves. Both previous rides were in the 60s with no jacket shoe covers or gloves. My average heart rate was 3 BPM higher yesterday than previous rides, so I think I was working at least as hard as previous rides.
Do you guys think the tire can make a difference? I am not obsessed with this, but it makes me wonder about the rotating mass. I am 6'2" and 255 pounds so it is a little hard to believe that a tire and shoe covers can make that much of a difference. I guess if I lost 40 pounds I could average 30 MPH.