If you're spending serious time above 5,000 RPM on track, your alternator is spinning itself into an early grave. Because the alternator pulley is smaller than the crank pulley, the alternator spins significantly faster than engine speed. That's a non-issue on the street. At sustained race RPM, it's a real liability for your bearings and brushes.
The R Theory Motorsports Underdrive Alternator Pulley brings that ratio back down by 36.5%. Your alternator stays well within its operating comfort zone, dramatically extending its service life over a full season of hard use. It's the kind of part that earns its money by saving you from a DNF and a bench rebuild.
Machined from 7075 aluminum, the same alloy used in aerospace structural components and race suspension hardware, and anodized in R Theory's signature blue. Despite the larger 92.45mm diameter versus the stock 58.70mm, it matches OEM weight exactly. No added rotational mass. Direct bolt-on replacement; just swap in a longer alternator belt and you're done.
Charging at idle remains adequate for race use. This pulley is designed for dedicated track and competition applications. We don't recommend it for street-driven cars that rely on the charging system for daily use. Made for the driver who finishes races, not just starts them.
What's Included:
- Underdrive Alternator Pulley (×1)
- Sticker Pack
