a continuously variable transmission is disclosed for use in rotationally or linearly powered machines and vehicles . the single axle transmission provides a simple manual shifting method for the user . an additional embodiment is disclosed which shifts automatically dependent upon the rotational speed of the wheel . further , the practical commercialization of traction roller transmissions requires improvements in the reliability , ease of shifting , function and simplicity of the transmission . the disclosed transmission may be used in vehicles such as automobiles , motorcycles , and bicycles . the transmission may , for example , be driven by a power transfer mechanism such as a sprocket , gear , pulley or lever , optionally driving a one way clutch attached at one end of the main shaft .