Friction drive pertains to a drive system where the motor's axle is pressed against the rubber of the bicycle's rear, or front, wheel.
(Friction; drive; pertains) (the motor's axle; is pressed; against the rubber of the bicycle's rear, or front, wheel; L:a drive system)
Friction the motor's axle
drive is pressed
pertains
against the rubber of the bicycle's rear, or front, wheel L:a drive system