A continuously variable transmission (CVT) can be used in concert with an electric motor to facilitate power assistance to a rider in a bicycle. In some embodiments, the CVT and motor is mounted on the frame of the bicycle at a location forward of the rear wheel hub of the bicycle. In some embodiments, the CVT is mounted on and supported by members of the bicycle frame such that the CVT is coaxial with the crankshaft of the bicycle. The crankshaft is configured to drive elements of the CVT, which are configured to operationally drive the traction rings and the traction planets. In some embodiments, the motor is configured to drive elements of the CVT. In other embodiments, the motor is configured to drive the crankshaft. Inventive component and subassemblies for such a CVT are disclosed.