Competition Clutch 2004-2011 Subaru STI 15lb Steel Flywheel - 2-721-ST

Competition Clutch Lightweight Steel Flywheel — Subaru STI 6-Speed, 15 lb (2-721-ST)

A one-piece 4140 forged steel flywheel at 15 lbs, stamped at 2000 tons and 1260 degrees, then CNC machined and balanced to OE specification.

One-piece construction is the durability argument. A two-piece flywheel has a pressed or welded ring gear that can separate, and a bolted friction surface that can warp. This is one forging, so neither failure mode exists. It can also be resurfaced when the clutch comes out.

The ST spec is the street spec. It sheds meaningful rotating mass from the crank — faster revs and noticeably improved engine response — while retaining enough inertia to preserve low-end torque and drivability. A car with this flywheel still pulls away from a stop normally, which matters on a heavy AWD chassis.

Recommended for naturally aspirated and street-driven applications, and well suited to Gravity, Stage 1, and Stage 2 clutch kits. Works with all performance and stock clutch assemblies.

Meets and exceeds SFI 1.5.

Fitment: 04-21 Subaru WRX STI, 6-speed. Also fits 6-speed swapped WRX chassis.

If the build is heavily boosted or track-focused, the ultralight STU version is machined with less material for quicker revving, suited to Stage 3 and up.

Sold individually. Flywheel bolts not included — worth replacing while it's apart.