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JB Racing Lightweight Steel Flywheel - Grand-Am Legal - E46, MZ3, Z4 ...

T#:40748575

Part#: 520010240SGA

Ships on Sep 3, 2026

$ 868.00 USD

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$ 868.00 USD

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This lightened steel flywheel is specifically designed (and approved) for use in Grand-Am road racing but can also be used as a mild street upgrade if a full aluminum lightweight flywheel is not called for. The Grand-Am flywheel is 20% lighter than stock to meet the rules for the GS and ST classes.Modern flywheels are built with additional components and features that are designed to dampen and minimize vibrations from the engine and transmission. As a result they have become bloated in weight and that means more energy is used up just making the flywheel spin. A lightweight flywheel does away with the dual mass design and its additional mass so more energy can be diverted to where it counts most - moving the car. The flywheel and clutch is one of the first areas that engine builders address when making the rotating assembly lighter for race engines. The dampening effect is just not needed on cars that are focused on performance.

In addition to releasing more power to the wheels, the lighter flywheel allows the engine to spin more freely, which improves throttle response. The engine revs much faster than before. With the engine spinning easier the power band comes up much sooner. The stock steel flywheel feels lazy in comparison. There is a driving adjustment required to get used to how much faster the engine revs but that's not really a downside.

Grand-Am approved this flywheel to be used with a factory E36 M3 clutch. This opens up a lot of clutch and pressure plate options but we typically used this with a stock Sachs OEM clutch kit. This makes replacement clutch components easy to source and inexpensive when compared to specialized racing clutches.

Lightweight flywheels are considered 'single-mass' flywheels because they do not have the same dampening designs as an original 'dual-mass' flywheel. With a single-mass design more noise and vibration may be noticeable. There are steps you can take to minimize the noise - heavier weight transmission oil and clutch discs with anti-rattle springs (sprung-hub clutch). In addition to the standard replacement clutches, we also sell Sachs Performance sprung hub clutches that also work with the JB flywheels.

If being used on a 330i 6-speed or Z4 6-speed an additional pilot bearing hub is required. Select your appropriate model and transmission from the list below.

Stock Flywheel Weight = 25.0lbs
JB Flywheel Weight = 20.0lbs

This item fits the following BMWs:
2001-2002 E46 BMW 330i 330ci 5-speed
2003-2006 E46 BMW 330i 330ci 6-speed
2001-2006 E46 BMW M3
1998-2002 Z3 BMW Z3 M Roadster M Coupe
2003-2005 E85 BMW Z4 2.5i Z4 3.0i

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Single Mass Flywheel

JB Racing Lightweight Steel Flywheel - Grand-Am Legal - E46, MZ3, Z4 ...

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