I have a Garmin 705 that I absolutely love. However, since updating my Powertap to ant + and transmitting power/cadence data to the device, it occasionally reads very high speeds, then corrects. No other data transmission errors, power, cadence and heart rate are all OK. I also have the garmin cadence sensor on the bike.
Do you think that it is double counting the information from the cadence sensor and powertap?
Any help is appreciated.