"Original weighs 3.2kg, this lightened bottom pulley is only 417grams!
The ALTA Performance™ lightened crank pulley for the MINI CooperS is engineered to reduce rotating mass, increasing horsepower and torque.
Made from 6061T6 aluminum and weighing less than the stock crank pulley, the ALTA pulley is not under driven and will not affect the life of your engine. The pulley is a redesigned, lighter rendering of the stock crank pulley, achieving power and performance by reducing the rotating mass of the crank assembly.
That reduction is effectively the same as removing 100 pounds of weight from your vehicle. The ALTA Performance™ pulley will not wear out engine bearings or the oil pump, and will not add any additional vibration or noise.

Aftermarket, under driven pulleys are prone to charging and drivability problems from being excessively under driven. The ALTA Performance™ lightened crank pulley will have no effect on your cars charging system.
To increase the boost pressure on your car, you can either reduce the supercharger pulley or fit this oversized crank pulley, or even use both. E.G. The 2% oversized pulley is equivalent to fitting a 15% pulley, or both together is like fitting a 17% pulley. The 3% oversized pulley will gain power increase between the two. N.B We do not recommend fitting any oversized crank pulley with the 19% supercharger pulley.