Originally Posted by Eatadonut
I can hit around 38mph on the flats without it being a big deal.
What I can't do is sustain that for more than a few seconds
But you don't need a 55 x 11 to hit 38mph for a few seconds. In a sprint of a few seconds, you're going to be wound up beyond 90 rpm. If your top sprint speed is 38, you're going to be fine with a 53x11 or even a 53 x 12.