Originally Posted by
daxr
Watch how the roadies do it - you pedal faster to go faster, about 90 rpm is a good goal, pushing whatever gear is comfortable for you. That's much easier on your muscles and body and with practice you can keep it up for longer periods, and you will get faster and feel better riding. It is very worthwhile to have a shop look at your position on the bike as well, as that makes a huge difference.
This, and try to mix it up during your ride. Get into a comfortable rhythm at about 90 rpms and then really push it on a slightly harder gear for a mile and then back off and get into that comfortable rhythm again. Give yourself a few miles between hard pushes.