I knew nothing about fixed gear bikes until about 6 months ago, when I bought a used one, so I may not be the best source. Mine came with a 42x16, which I laughed at when I first saw, thinking something like 53x16 might be more appropriate.

Was I ever wrong. 42x16 is plenty, once you work on your spin and figure out how to go fast in a gear like that. Where I ride the bike is dead flat too, the wind is the only thing I need to worry about. And I'll tell you, fighting a 15-20 mph headwind in a 42x16 fixed gear will definitely tire you out. And if your knees flare up, too bad, you gotta keep pedaling.

What I'm most amazed at is how is easy it is to vary your speed so much, with just one gear. And how tiring it is to sprint, but not be able to coast afterward. Also the danger, I still catch myself trying to coast, and having my leg jerked back into motion. Especially when something happens quickly and I react purely on instinct. Old habits die hard, so watch out for that.