i'm not trying to rain on your parade, but you need to get out more! and you need to qualify your statement. My fastest ride would be 1 second, the time I got on my bike, discovered the rear tire was flat, and was late for work so had to take a cab.

To get more specific, I have a 6mile loop incentral park that our cycling club uses 4 laps of as a way to categorize you for group rides. My personal best is about 1hr and 23 minutes for 4 laps which is a shade of 18mph. I'm pretty spent after going that hard on it but there are so many variables, temperature, is it wet out, wind, etc.

BTW, I'm 235lbs.