Road Cycling - Two rides, different average

How can two riders that start at the same time and finish together have different ride speed average? If I do simple math, distance/time I should always get same answer.
It sounds like a joke... but it is a real question that comes up at almost every club ride I do when people compare averages.

…and yes I am assuming that the cycle computers are accurate…

If one person rides quicker to a regroup spot and waits up, they'll have a faster average than someone who reaches the spot later. Assuming their calculators are set to only record when moving. One option I guess.

If one person rides quicker to a regroup spot and waits up, they'll have a faster average than someone who reaches the spot later. Assuming their calculators are set to only record when moving. One option I guess.

When my wife and I are out on long weekend rides, this is exactly what happens.

This is the only possible reason (aside from inaccurate computers). Most bike computers (at least mine does this) stop when you stop. If you checked the actual time riding which is used for the average speed calculation you should find a difference which is attributable to different amounts of stoppage time.


If one person rides quicker to a regroup spot and waits up, they'll have a faster average than someone who reaches the spot later. Assuming their calculators are set to only record when moving. One option I guess.

Are the mileages the same? On our club rides, the faster riders will often turn around to round up the stragglers at various points along the route. (This usually occurs on a long climb.) In this case they finish at the same time but end up putting in more miles.

Well, being a gadget junky, I have two computers on my bike, Shimano Flightdeck and Forerunner 201. Although they function on two very different principals, my average on both is always same, SLOW. :p

another thing is on longer rides (especially ones where you are turning a lot) sometimes your distance will come up different every time you take the route. i have routes that will vary up to 2km just based on if i take corners sharp or if i take them wide and other where i am on the road situations. in a group the same things sort of happens. the people who are always on the inside corner will have less distance travelled than the people on the outside

How can two riders that start at the same time and finish together have different ride speed average? If I do simple math, distance/time I should always get same answer.
It sounds like a joke... but it is a real question that comes up at almost every club ride I do when people compare averages.

…and yes I am assuming that the cycle computers are accurate…

Maybe on one of the computers the "tire calibration" is set wrong. Maybe you have the wrong wheel size calibrated on your computer? I have a Cat Eye OS 1.1 and so does my sister and we would always start at the same time and always have different average speeds at the end of the ride, so I checked her tire settings and her tire settings were for a larger wheelset. I corrected it and now she's slower than me which I always knew she was!!

That could be a possibility, no?

Well there are a number of reasons.

Comparison is best done with people who rode in the same groups and stopped at the same rest stops and so on.

1) Tire calibration is one reason, but I think it is probably pretty minor.

For average speed, most computers cut off at a certain minimum speed and start up again at a certain minimum also some computers click off faster after having stopped then others. Even a small amount of low speed riding will affect your average. So even riding style will make a difference, even in the same group. You might have one person who rides relatively fast to the stop and then stops pretty abruptly. His buddy slows gradually and kinda coasts in at a low speed. Just that action could easily produce a difference in average speed of a few tenths of an MPH in the course of a ride.

How can two riders that start at the same time and finish together have different ride speed average? If I do simple math, distance/time I should always get same answer.
It sounds like a joke... but it is a real question that comes up at almost every club ride I do when people compare averages.

…and yes I am assuming that the cycle computers are accurate…

It could also be when the reset their average speed - if I roll or walk across the parking lot, my average will drop .3-.4 mph. Often times I'll reset my average after we roll through town and actually start riding.

You are right, it you reset them and you have the same mileage and time, the average should be the same :rolleyes:

-murray