I would have guessed about 80mph.

The answer is 166.9 mph. Set by Fred Rompelberg in 1995.

They actually start out by towing the guy behind a dragster that has a tail fairing that protects the rider, ensuring virtually no wind resistance. He then releases himself when up to speed and continues pedaling. That speed is the speed he can maintain on his own.

I was totally shocked - shows what a great machine the bicycle is.