Mountain Bike Power Meter App Test Ride At The Wausau 24

With the Cykelstrom mountain bike power meter app revision 1.30 completed and tested on the local single track, it was time to give our app a test at the Wausau 24 endurance mountain biking race. I captured video of the first lap and included results for the first two laps of the race.

Video of the first lap of the Wausau 24 Endurance Mountain Bike Race

Mountain Bike Power Meter App Accuracy For Lap One

Sensors	Crank Power Meter (Watts avg.)	Cykelstrom (Watts avg.)	Difference (Watts)	Margin of Error (Watts)
External Speed and Cadence	116.7	123.8	7.1	+/- 3.6
GPS Speed and External Cadence	116.7	101.5	– 15.2	+/- 3.4
External Speed Only	119.2	146.7	27.5	+/- 4.2
GPS Speed Only	119.2	119.7	0.5	+/- 3.9

Table created using Bland-Altman Analysis using a 4iiii Precision Pro single sided crank power meter as the standard with 95% confidence level.

Mountain Bike Power Meter App Accuracy For Lap Two

Sensors	Crank Power Meter (Watts avg.)	Cykelstrom (Watts avg.)	Difference (Watts)	Margin of Error (Watts)
External Speed and Cadence	121.3	141.5	20.2	+/- 3.5
GPS Speed and External Cadence	121.3	109.1	– 12.2	+/- 3.3
External Speed Only	122.8	164.4	41.6	+/- 4.0
GPS Speed Only	122.8	128.0	5.1	+/- 3.8

Table created using Bland-Altman Analysis using a 4iiii Precision Pro single sided crank power meter as the standard with 95% confidence level.

Discussion Of This Ride’s Results

This test ride of Cykelstrom, demonstrates the challenges estimating power when riding in extreme conditions, like a heavy canopy.

During the ride, GPS reception was poor as indicated by the heading information using the magnetometer instead of GPS most of the time. Cykelstrom looks at the accuracy of the GPS heading information and will switch to the magnetometer if accuracy is low. It appears that since GPS accuracy was low, then other GPS derived data was not updated frequently enough to give good power estimates. For this reason, I recommend users of the Cykelstrom App use an external speed sensor and cadence sensor when GPS signals are unreliable. To learn how to add external Bluetooth sensors to Cykelstrom please visit Adding Bluetooth Sensors to Cykelstrom.

When using an external speed and cadence sensor, accuracy was greatly improved for this ride. The Cykelstrom mountain bike power meter app was within 6% at best and 17% at worst, on average, when compared to the standard crank power meter.

As the developer of Cykelstrom, I ride every opportunity possible to improve the app. Your suggestions and feedback are welcome at developer@cykelstrom.com.

Strava Activity

Click on the map to visit this activity in Strava. Feel free to follow all of our test rides of the Cykelstrom Bike Power Meter App. This is lap one of the Wausau 24 Race.