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JB Racing Aluminum Lightweight Flywheel – 128i, 325i/328i/330i, 525i/528i/530i, Z4

Upgrade your BMW’s performance with the JB Racing Aluminum Lightweight Flywheel. Designed as a direct replacement for BMW part #21207573785, this flywheel dramatically reduces the heavy rotating mass found in stock units on E82 128i, E90/E92 325i/328i/330i, E60 525i/528i/530i, and Z4 models with the N52 engine. The result? Quicker revs, smoother shifts, and effortless rev-matching once you get used to the reduced weight.

Engineered for street-driven performance, JB Racing’s lightweight flywheels reduce both overall weight and Moment of Inertia (MOI), helping the engine spin up faster and freeing up more power to reach the wheels.

Precision-built from billet aluminum and designed as a single-mass unit, each flywheel mirrors OEM specs and is compatible with original clutch components. Every flywheel is CNC machined, balanced, and assembled in JB Racing’s U.S.-based facility known for its work with top-tier race teams.

Key Features:

• CNC machined and zero-balanced to eliminate vibrations

• Replaceable hardened steel clutch surface (bolted, not riveted)

• Heli-coil inserts to prevent thread stripping during clutch changes

• Factory-spec starter ring gear

• Hardened steel gall plate protects bolt interfaces

• Includes flywheel bolts, pressure plate bolts, and captive 10mm dowel pins

• All hardware is metric

• Weighs only 12 lbs vs. the stock 31.2 lbs

• Made in the USA with race-proven precision

Note: For best performance and reduced drivetrain noise, we recommend using a sprung-hub clutch disc with this flywheel.