Abstract: A multi-speed transmission is provided which employs inflatable diaphragms to alter drive ratio. Particularly applicable to bicycles, the transmission is composed of a diaphragm mounted at the pedal axis and another mounted at the drive wheel axis, with a nylon drive belt connecting the two. These diaphragms are each inflated and deflated by way of pressurized cylinders mounted on the bicycle. Pedaling of the bicycle turns the pedal axis diaphragm which, in turn, drives the rear wheel diaphragm via a nylon drive belt. Pressure tubes carry the pressurized fluids from each of the cylinders to their respective diaphragm. Standard shifter mechanisms are used each of which, when moved, moves a piston within one of the cylinders, changing the pressure in that cylinder and the inflation of its respective diaphragm.