Shimano E6100 average speed calculation


Active Member
On my Kona Dew-e DL with Shimano E6100 I've noticed that the average speed displayed after a ride doesn't match with what a standard speed/distance/time calculator would give. For example, after a ride of 18.5 miles and 1 hour, 11 mins, my display showed an average speed of 15.9 mph. However, if I input the time and distance into a calculator like this one: Calculator Soup, the average speed is 15.6338.

Does anyone know or have a theory about what would cause this discrepancy? Is the E6100 doing something interesting, like not counting very slow speeds (while starting out or slowing to a stop)? It's not a huge deal but just a curiosity to me. The display always reads high, but inconsistently so...sometimes it's only off about about .1 mph, other times more than that, like in the example above. TIA.
You might need to adjust the circumference of your tires in your controller. Or, it may be that your bike is only calculating moving time, not overall time.

As you say, it's probably not a big enough deal to worry about a lot. If either of my ideas apply you will probably not ever get a whole lot of precision.

Thanks @Tars Tarkas. Unfortunately, Shimano does not allow the end user to adjust the tire circumference; it's built in. And the fact that it's measuring distance correctly (based on a comparison with my husband's cyclometer, which we've checked on a couple of measured routes) shows that that is not the issue. I know that it is only calculating moving time, which is what one would want, since a long stop at a light, for example, should not be included in ride time or average speed, at least in my opinion. A long, long time ago, I had a bike computer that didn't automatically shut off at stops; one had to remember to do that manually, and I usually forgot, so if we stopped for ice cream, the ride time would include that long period of time at zero mph, making the calculated average speed much lower than the actual ride speed at the end of a ride. But my Shimano is doing the opposite; showing a higher average than what I calculate from the same ride time and distance.

Again, not a big deal, more of a curiosity. Inquiring minds and all that!