Why does the e-bike display’s odometer reading differ from the GPS device’s measurement?

The e-bike calculates distance and speed based on the wheel circumference using a speed sensor. At the factory, the wheel circumference is set according to the original equipment tyre and the assumption that the tyre compresses slightly while riding.

Depending on tyre pressure and the load on the bike, the actual wheel circumference may vary slightly. If the bike is fitted with a different tyre, the wheel circumference will also change. The measurement tolerance permitted by Shimano is approximately 4%.

A GPS device calculates distance based on the GPS signal. Accuracy is affected by signal strength. All GPS devices have a certain measurement tolerance, which affects the recorded result.

Therefore, it is to be expected that the measurement results will not match exactly.