Abstract: A friction drive system for a bicycle, which enables a bicycle to be converted into an electrically assisted bicycle, includes a driving system including a friction roller in driven engagement with a motor of the driving system. The friction roller defines a wheel engaging surface configured for engaging a wheel of the bicycle via friction between the wheel engaging surface and the wheel. A controller is operatively connected to a traction control system, for controlling a torque exerted by the friction roller on the wheel, and/or to an adjustable pressure system, for moving the wheel engaging surface and varying a contact force exerted between the friction roller and the wheel of the bicycle.