The Reactiv from CT Drives is an active alternator decoupling-type pulley that reduces NVH by decoupling the normal engine crankshaft vibrations and variations of the engine’s compression and by firing strokes from the inertia of the alternator rotor. The high apparent moment of inertia of the alternator rotor resists sudden speed changes, stressing the accessory drive belt and belt tensioner and the accessories being driven by this belt. The Reactiv pulley relieves these stresses by incorporating a tuned, bidirectional spring connection between the pulley’s belt-driven outer circumference and its inner connection, transmitting the average speed of the crankshaft to the alternator rotor while preventing coupling of the vibration to the shaft. Features include lack of hysteresis, effectiveness under extreme underhood temperatures, and functionality without lubrication. Pulleys are offered in various sizes to fit most applications.