12.3% (57mm) SC Reduction Pulley
Finally a just right size pulley; small enough to increase boost by a worthwhile amount, but large enough to keep inlet air temps at high rpm manageable, and increased wear rates to a minimum. Only 1mm smaller than the BMW engineered JCW pulley, with the exact same land & groove geometry as OEM. Its manufactured with special steel designed specifically for poly-grooved belts. The most common MINI aftermarket pulley material Stainless Steel is attractive and will not rust, but it has a slippery quality, and lacks the same thermal expansion character as the supercharger shaft.