You start the computer for time and distance when you start the ride and stop it at the finish. Averages for any ride are based on elapsed riding time.

Here are a few things riders do:

1. Take snapshots of their ride when their average speed is what they say when their overall average is much lower.

2. Fail to change the setting on their computers from km/h to mph (and yes, it does happen as one poster recently admitted on another thread).

3. Take the average reading from their computer for the ride, when the computer stops time when the bike stops moving. Related to this, it takes two or three seconds for the computer to get up to speed again after stopping. Do that 20 or 30 times on a ride and you've saved up to 60 seconds.

4. Have a burning desire to fit in with others who may or may not be averaging the speed they quote.

5. Always ride within the peloton on a group ride and never take a pull. They are always riding easy, being dragged along by the guys actually doing the work.

6. Ride on the flats all the time and often with a tailwind.

7. Are just plain liars.

There definitely are guys who can average the fast speeds. In the over-50 groups, they usually have been through the mill as racers, are very lean, and ride often. They know how to pace themselves, know the hydration and nutrition drills, and have superb roadcraft.

If you want to use averages as a guide to fitness, you should do a series of time trials of between 8 and 10 miles, on a flat route, in as close to identical conditions on a bike as close as identical each time, and at the hardest you can ride. But then, of course, unless your peers do the same route in the same conditions, the result is irrelevant, except as a measure of your fitness and speed.

And that's the crux of the whole thing... in the end, averages are comparatively meaningless because there are so many variables in ride conditions.