Originally Posted by billridesbikes

The cadence/speed sensors that attach to the chain stay are always finicky for me. If it gets knocked even a little off position you lose speed or cadence, have to stop and adjust, usually at the worst time. The Garmin speed2 and cadence2 sensor or similar Wahoo one is better and fool proof and you can connect to a smart phone app like ridewithGPS or Strava instead of needing a bike head unit. If you get more serious you can invest in a Garmin or Wahoo bike computer later.