Are you allowed to shift? There was a drag racing series a bunch of fixie guys put on here a few years ago and you could use a road bike, but you weren't allowed to shift. A local shop owner, who is an ex-olympian track racer, recommended a gear ratio of approx 3:1, which if you had a 53 would be an 17 or 18 in back. The main thing is the trade off between quick acceleration, and not being at too high of a cadence when you get up to speed.

Edit: Oh yeah, I have some videos from it...