I agree that it totally depends on the bike. I used to ride 16-18 mph on my cannondale. On the mountain bike with knobbies, it was more like 12mph. On my cattrike speed, I average 10mph and am thrilled with the speed on 20" tires and 3" ground clearance from my girlie parts. Your speed is your speed. Ride enough to get sweaty but not so hard that you can't get home. Enjoy!