Joined: Jan 2009
Posts: 44,199
Likes: 6,436
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
[MENTION=252435]RubeRad[/MENTION], a body in motion tends to stay in motion, but air resistance acts against it. To maintain speed, we have to accelerate slightly, constantly. That's why weight matters. It doesn't always matter as much as we expect, but it definitely matters. You can do experiments to verify this.
I'm thin, and I have a hard time keeping up with bigger people on the flats, so I figure my surface area to mass ratio is my problem. Or more likely, it's my surface area to power ratio. Of course, I'm pretty decent at climbing hills. I'm also very good at descending, and I don't know why that is.
Hill and air drag advantages don't really add up on a bike commute, since you have to reverse. Maybe one way is faster than the other, and in that case, 20 mph is very impressive if you can do it both ways. If you can do it only one way, I will guess you have some big downhills on that route.