The drive sheave, also called the traction sheave or pulley, is the grooved wheel mounted on the shaft of the traction machine over which the elevator suspension ropes (or belts) pass. Friction (traction) between the ropes and the grooves of the sheave transfers the motor torque to move the car and counterweight in opposite directions. Sheave groove profile (semicircular, undercut, V-groove) determines the traction coefficient and rope wear characteristics. The drive sheave diameter, groove pitch, and material are critical design parameters.