I just got a new bike (more on that later), and I've taken two rides on it so far with a friend. I commute by bike to work, and I've raced another bike I recently sold in a crit series. The two rides I've done the last couple days were around 60 miles, and I know that sounds like a lot, but I'm currently running four miles at the moment, so 60 miles really is within my fitness level.

About 10 miles into the ride my back started to hurt both rides. It always hurts when I'm working harder to sustain my speed. I think my bike fits fiine. I'm 5'9 and ride a 55cm, and have long arms. I know I can't rule out the fit, but I think it's more because I haven't ridden in a while. My back doesn't bother me much when I'm riding at slower speeds of 14mph or so.

Does anyone else who sits through a long snowy winter have these problems early in the season?