Combined Bluetooth Speed / Cadence Sensor
I use the Sportplus Speed / Cadence Sensor SP-SPD-BLE-100 .
For combined sensors there is no option to change the wheelsize in the Bluetooth-Manager. For single speed-sensors there is the option to change the wheelsize.
After the track is exported to velohero.com, the cadence is shown correctly, but speed is far too high because I'm using 20" wheels.