A method of operating a vehicle at different altitudes. The vehicle has an engine, a throttle valve and a throttle operator. A continuously variable transmission has a driving pulley connected to the engine, a driven pulley, and a belt operatively connecting therebetween. A ground engaging member is operatively connected to the driven pulley. A piston is connected to the driving pulley. A control unit controls actuation of the piston and the piston force. The method includes determining an altitude and/or an atmospheric pressure, a driven pulley speed, and at least one of the throttle operator position and the throttle valve position. The piston is selectively actuated based on the altitude and/or the atmospheric pressure. The piston force is controlled based on the driven pulley speed, and at least one of: the throttle operator position and the throttle valve position. Vehicles and other methods of operation thereof are also disclosed.