8.25 mph / 13.27 kph is the casual cruising speed on flat pavement.
I went to a bike trail for the first time and had some long runs, which I hadn't been able to do on city streets.
4 mph / 6.5 kph is the fall over speed, anything less and you aren't peddling.
5 mph / 8 kph is the comfortable pace up a mild slope, without any substantial exertion.
8-10 mph / 13-16 kph is the maximum sustained cruising speed on flat pavement with negligible wind.
10.5-12 mph / 17-19.3 kph is the fastest I have ever been able to maintain a pedal.
This speed is my standard for peddling down a gentle slope, or maintaining a strong pace for the workout. This is the leg burning pace.
If you are a biker, or riding for a workout, this is the speed you will be maintaining in lite wind.
12.5-15 mph / 20.1-24.1 kph this is over running the pedaling, I am incapable of peddling at a speed fast enough to contribute to the speed of the wheels. you need a strong tailwind or decent hill to get to this speed.
15 mph / 24kph + time to get a helmet
My own top speed recorded by the meter in as long as I've had it on the bike is 14.4 mph / 23.1 kph and that is with a few steep hills I couldn't contribute any more speed to.
http://abikecentral.com/forum/viewtopic.php?t=200
My method of attaching a speedometer to the a-bike.