Transmission Speedometer shafts are important components of a motorbike's transmission that measure the speed of the motorbike and transmit it to the speedometer. The shaft is usually attached to the gearbox or front wheel and uses a system of gears to measure the speed of the motorbike. Accurate measurement of speed is important for safety and effective use of the motorbike. Gearbox speedometer shafts need to be checked regularly and replaced if necessary to ensure an accurate measurement of speed. There are also electronic speedometers that measure speed via sensors on the wheel.