# Why is mileage in Xert double Garmin 1030 even though speed is the same?

I have a Wahoo Kickr and use a Garmin 1030 and Xert on my Android phone. At the end of an Xert structured ride the mileage according to Xert is almost exactly double than the Garmin. The speeds seem close to identical on both the phone and Garmin as I ride but the distance on Xert is double. What’s up?

The distance/speed is based on what your headunit or app has set as “wheel diameter”. It’s not very meaningful - power is the key metric for doing indoor training. Apps like Zwift, Rouvy, etc will also have their own computations of distance based on power, gradient, weight, etc.

Is Speed from Power enabled on the Android app?

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Something is wrong with Xert’s math. I understand that speed is somewhat meaningless on a trainer. By picking the right gearing in ERG mode I can create realistic speeds which in turn create realistic distances.

The speed displayed on my Garmin 1030 and the speed displayed on my Xert Android app is very close. However, the distance calculated by Xert is double. For example, yesterday’s workout.

Xert: Time: 52:14 Avg speed: 17.5: Distance: 31.06 miles (Loaded directly from Xert app)

No matter how you slice it, distance should have been a bit more than 15 miles not 31.06.

Training Peaks: Time: 51:58, Avg speed: 17.7, Distance: 15.3 (from Garmin 1030)

I find that the speed from power is a little generous. I’m okay with the ego boost, recognizing that - on a trainer - speed is nothing more than a curiosity when you’re not actually moving anywhere!

As a matter of interest what was your average power on that workout?

Avg. power was about 190. But the issue is simply a matter of math and Xert is doing something odd.

Xert has the correct speed, about 17.5 mph. That is what was displayed on my Android phone Xert app. and is very close to speed shown on my Garmin 1030. Avg. speed of 17.5 mph for 52 minutes will never equal 31 miles. It doesn’t compute.