Lightweight aircraft grade alumimium Lightened Underdrive Pulley Kit (3 pulleys and belts included). Suits WRX/STi MY99-00, Forester GT MY01-02
Most of Go Fast Bits kits are underdriven, which means the accessories are driven slightly slower to reduce parasitic losses. GFB pulley kits are designed to improve acceleration by reducing the rotational mass (inertia) on the crankshaft as well as parasitic loads from the driven accessories. The effect is similar to a lighter flywheel, and the engine feels more lively and willing to rev.
The underdrive ratios have been optimised to ensure there are NO adverse effects on the performance of the accessories, and whilst it is true that some engine types do suffer harmonic issues from lightweight pulleys, we steer clear of those. The kits we release are thoroughly application tested and do NOT cause engine damage in the short or long term.