I actually posted something about this a couple months ago. I found that I was spinning around 60rpm when I bought my Edge 500 with cadence sensor. 90rpm seemed like an impossibility.

One forum member said it wasn't an aerobic thing and to just spin faster and I was kind of ticked off about it. Well he was RIGHT! I just started to push it. 60 was comfortable. 70 was pushing it. So I forced myself out of my comfort zone on every single ride.

So what happened? Last Friday I had my first ever AVERAGE of 100rpm for a 1.5 hour ride. No hills, just underpasses, but that was a record for me. 90rpm is every ride now. No problems. It really does just come with time.

Also, my weight has dropped noticeably since I'm getting a couple hours of serious cardio now that I don't take coasting breaks or spin slowly. Now it's a game. I want to average 110 on just ONE ride. I think it will take a couple months but I can do it. 95-100 just feels so natural now.

Good luck with it. Just push yoursef. I didn't want to but sure am glad I did!