In order to provide smoother transition for speed changes, a variable speed pulley having a movable sheave half and a fixed sheave half is provided with a torque cam. A spring biases the second sheave half axially of the first sheave to vary the width of a belt receiving groove. The torque cam forces the second sheave half in the same direction as the spring when the torque of a load operatively connected into the pulley assembly is increased. A centrifugal thrust arrangement urges the second sheave half in a direction reverse to the direction caused by the spring responsive to the rotational speed of the pulley.