Abstract: The variable speed transmission is for transmitting a torque produced by an engine to a belt. The transmission comprises a shaft connected to the engine, a fixed flange and a movable flange slidably connected to the shaft and substantially rotatable thereon. The flanges define therebetween a groove for receiving the belt. A pressure device is rigidly connected to the movable flange. The pressure device has a pair of pressure units diametrically opposed for pressurizing fluids. Each pressure unit comprises a first fluid chamber, a second fluid chamber, a radially movable partition separating the first fluid chamber from the second fluid chamber, resilient means for applying a return force toward the shaft counterbalancing the centrifugal force, and a fixed partition rigidly connected to the shaft. The fixed partition also separates the first fluid chamber from the second fluid chamber.