How do Garmin Speed Sensors Measure Speed?

The Garmin Bike Speed Sensor and Speed Sensor 2 use a magnetometer to detect the sensor's rotation within Earth's consistent magnetic field. Since Earth's magnetic field is stable during a ride, the sensor primarily focuses on its own movement. Global consistency checks are in place to ensure the sensor is always reading the Earth's field, not other magnetic interference.

Will Riding Around Metal Objects Such as a Steel Fence or Manhole Cover Affect the Accuracy of the Sensor?

No, Garmin speed sensors are designed to accurately track wheel rotation even when near magnetic materials like steel fences or manhole covers. Testing shows these rarely cause errors.

What About Indoor Trainers That Feature Magnets?

Garmin speed sensors work correctly with magnetic fluid trainers. The sensor automatically calibrates after 3 minutes of stillness to minimize interference from magnetized bike components.

Are There Any Other Potential Cases of Interference?

• Dynamo Hubs: Avoid mounting the sensor over a dynamo hub, as its magnetic components will interfere. Use the other wheel instead.

• Other Sensors/Magnets: Limit the use of other magnets near the sensor. Stronger magnets need greater distance. Ideally, remove all other magnets from the bike. If necessary, move the sensor to the other wheel.

• Magnetized Bike Components: If a bike component (hub, cassette, chain, etc.) has become strongly magnetized, it can interfere. In this case, mount the Garmin sensor on the other wheel.