When I started riding in 1995, I was in my mid 20's, weighed 235lbs and was in the best shape of my life and my average speed was always 9-11 mph. Now, I'm 47, weigh 400 lbs and my average speed is still 9-11 mph!

Some of this is probably my riding style with constant slowing down and accelerating. I literally never get on a straight road and just ride at a constant speed. The closest I've gotten to that was a 10 mile multi-use path, when I had some pretty decent (ie, light and high quality) tires on the bike and I averaged 13mph for that 10 miles.