Abstract: A chainless drive mechanism for a bicycle using a rotatable drive shaft for transferring the pedal actuated driving force from the pedal crankshaft to the rear wheel including shift mechanisms to provide different drive ratios. A pair of discs, each formed with a plurality of concentric series of openings, are mounted on the pedal crankshaft and rear wheel, respectively. A pair of spaced sprocket gears is rotatably mounted on each end of the drive shaft and engaged with a respective series of disc openings. A pair of axially movable ratchet slip gears is fixed against rotation on each end of the drive shaft adjacent a similar ratchet surface formed on each of the sprocket gears. A pair of operator controlled individual shift brackets is movably mounted on the drive shaft, each being operatively engageable with a respective pair of ratchet slip gears.