If the iGPSPORT Speed Sensor (SPD61)  or Cadence Sensor (C61) is not providing accurate speed information, review the following steps which will solve most problems:

1. Ensure the device is configured with the correct wheel size.

This setting is typically automatically set by the sensor.

Refer to details on wheel size and circumference. 

2. Remove any magnets installed on the bicycle.

3. Place the sensor on the front wheel of the bicycle.

This will move the sensor furthest from any components which may be magnetized.

4. Make sure the sensor is correctly installed on the front wheel.

If the sensor must be placed on the rear wheel (indoor training), place the unit with the sensor's LED closest to the cassette.

This moves the magnetic sensor further from any potentially magnetized components.

5. Leave the sensor stationary for 3 minutes after installing it, and then try again.

This allows the sensor to re-calibrate its internal settings to allow for bike-specific differences and minimize the effect of any magnetized components on the bike.

6. In some geographic locations in Ecuador, Peru, Brazil, or other locations, the earth's magnetic field is relatively weak and oriented in a north-south direction.

This makes it challenging for the BSS to accurately detect wheel rotations when moving in an east-west direction.