14. The next step was to mount the proximity sensor on the swingarm. This device senses the pulley bolts passing closely by its face, sending a signal to the computer to calculate speed. This sensor can see 4,000 transitions per second; a bit faster than the bike can spin these bolts. Placement is critical here as the sensor must ride no further than 5mm from the pulley bolts. On Cush-Drive models (’07-later), a different bracket is used that tracks the rear rotor bolts since there are no pulley bolts on Cush-Drive bikes.