I once did over 33 mph on A Specialized Roubaix with Ksyrium Equipe wheels (so unaero). That was a bike that was one or 2 sizes too big, as well, but I had clipless setup and sprinting is done out of the saddle anyways. Could very likely be faster on a similar bike that fits as I get very low when I start my sprint and my chin was nearly hitting the stem on that bike