Collection: PULLEYS & BELTS

Underdrive & Lightweight Crank Pulleys: Reduce Rotational Mass, Gain Real Performance

Underdrive and lightweight crank pulleys are precision-engineered upgrades designed to improve engine efficiency by reducing rotational mass and parasitic drag. The factory crank pulley is often heavy and oversized, which means your engine spends extra energy spinning accessories like the alternator, power steering pump, and water pump. By replacing it with a lightweight aluminum pulley and slightly underdriving accessory speeds, you free up horsepower that would otherwise be lost to accessory load. This results in better throttle response, quicker revs, and measurable horsepower gains without internal engine modifications.

The science behind the upgrade is simple: reducing the diameter and weight of the crank pulley lowers the inertia of the rotating assembly. Less inertia means the engine can accelerate faster, improving RPM responsiveness and overall performance. Underdrive pulleys typically slow accessory drive speeds by 10–20%, which reduces strain on components while maintaining safe operating ranges. Combined with a high-quality serpentine belt, this upgrade enhances reliability and efficiency for both street and track applications.

Benefits include:

• Reduced rotational mass for faster engine acceleration
• Lower accessory drag for improved horsepower and torque
• Enhanced fuel efficiency under normal driving conditions
• Durable construction for long-term reliability

Whether you’re looking for a performance pulley kit, underdrive crank pulley, or lightweight accessory pulleys, STILLEN offers premium solutions engineered for perfect fitment and maximum gains. Upgrade today and experience the difference in power delivery and engine response.