The answer is actually 42...

After 10-years of training, I can hit 38mph on perfect flat straight with no wind (verified by going both ways). In a crit, that usually translates into ~45mph with drafting. There's a guy here who posted a video of hitting +40mph by himself on a straight. What a monster! Was it PatentCAD? Waterrockets? Cypress? Can't quite remember.

As for actual sprinting-success in a race? Forget about speed, it's really irrelevant. I've beaten guys way stronger than me and been beaten my scrawny geek-types. About +90% of race wins are from mental tactics and strategies, not strength and outright speed:

- are you drafting the entire time? Even to move up positions?
- are you staying near the top 10-20 in the pack?
- are you staying off the brakes in corners and using maximum-speed out of the corners? (results in max-speed down the straights with little energy)
- are you watching and counting the top-5 guys who win each prime?
- are you following the guy who will get 2nd-place behind you on the last lap?

While lower cats may go a decently fast average-clip, it's the lows and highs that really determines how you hang on. Cat-4/5/6 can range in speed from 15-35mph+. Cat-1/2/3/p will range from 10-45mph+. You need to be training with these ranges in mind. How often are you doing sprints per week? How often are you doing anaerobic-intervals? Those are the training-days that will allow you to finish and win the lower cats. Look up Waterrocket's Training Bible in the Training section. If you spend all your training time at LT/AT going your average-speed, that's the fastest you're gonna go in a race. Heck, in a lot of my 4/3 races, we'll start off with a TTT at 10-20% above LT/AT at 28-30mph for 2-3 laps to burn off pack-fodder.