With the Bryton Dual Sensor - Speed & Cadence Sensor, you can add cadence data to your riding and eliminates speed spikes caused by intermitent GPS signal. The Bryton Cadence and Speed sensors require no magnets on your wheels or sensors to be placed on the chainstay. The Speed sensor can be installed on either the front or rear hub of your bike, whilst the Cadence sensor is installed on the left crank.