Spec BMW 323/325/328/330/525/528/530/M3/X5/Z3/Z4 Steel Flywheel
SPEC SB64S is a single-mass steel flywheel for the manual-transmission BMW sixes of roughly 1999 to 2006: the E46 323i, 325i, 328i, 330i and M3, the E39 525i, 528i and 530i, the five-speed X5 and the Z3. Owners shopping for it usually have a dual-mass flywheel that rattles at idle or shudders on takeoff, a clutch that needs replacing at the same time, and a power level or driving style that calls for something stronger and simpler than a new dual-mass unit.
The factory flywheel on these cars is a dual-mass design: two halves joined by arc springs and a bearing that filter engine pulses before they reach the gearbox. It is smooth when new, but the springs and bearing wear, and once it has excessive play it cannot be resurfaced. The SB64S replaces it with a one-piece steel flywheel that has nothing inside to wear out and can be resurfaced at future clutch jobs. SPEC lists its weight at 22 lb.
Because a single-mass flywheel removes the springs, the damping has to come from the clutch disc instead. SPEC's application chart for SB64S notes most fitments as being for use with a single-mass setup, which means it is meant to be paired with a clutch built for a single-mass flywheel, not the factory clutch from a dual-mass car. Expect a little more gear rattle at idle in neutral than a fresh dual-mass flywheel; that is the normal trade-off.
A dual-mass flywheel is checked with the gearbox out by turning and rocking the secondary mass by hand and comparing the free play to the limit for your car. If the clutch is the bigger concern, do a full-throttle roll-on in a high gear: rpm climbing faster than road speed means the disc is slipping. Our slipping diagnosis guide explains that test, and what a clutch job costs helps you compare a single-mass conversion with factory parts.
SPEC lists SB64S for the 1999-2000 E46 323, the 2000-2005 E46 325i and Ci five-speed, the E46 328 from April 1999 through 2000, the 2001-2003 E39 525 and 530, the 1999-2000 E39 528, the 2001-2006 E46 M3 six-speed and SMG, the 2001-2004 X5 five-speed, the 1999-2001 Z3 2.5L, the Z3 2.8L from October 1998 production through 2000, and the 2001-2002 Z3 3.0L. SPEC's chart also includes Z4 M entries with special notes. Production dates matter on these cars: an E46 328 built before April 1999 or a Z3 2.8 built before October 1998 is cataloged differently, and the 2003-2006 six-speed 325i and 330i ZHP are covered by SPEC's separate SB07S flywheel. Send us your year and VIN and we will confirm fit. More parts are in our hard parts collection.
While the gearbox is out on an E46, many owners also replace the driveshaft flex disc and center bearing, since the driveshaft has to come down anyway.
| Brand | SPEC |
| Part number | SB64S |
| Fits | Spec BMW 323/325/328/330/525/528/530/M3/X5/Z3/Z4 Steel Flywheel |
| Type | Flywheels |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
SPEC's chart lists SB64S for use with single-mass clutch setups. A factory clutch from a dual-mass car relies on the flywheel springs for damping, so pair this flywheel with a clutch kit built for a single-mass flywheel.
SPEC lists it at 22 lb. It is a steel flywheel, so it can be resurfaced at future clutch jobs.
SB64S is not listed for the E46 six-speed 325i or 330i. SPEC lists its SB07S steel flywheel for the 2003-2006 325 six-speed and the 330 six-speed ZHP. Send us your VIN if you are unsure which gearbox you have.
Usually a little. Without the dual-mass springs you may hear more gear rattle at idle in neutral, and the drivetrain can feel firmer on takeoff. Most owners find it acceptable in exchange for a flywheel that does not wear out.
SPEC lists the E46 328 from April 1999 on. Earlier 1999 cars, including the last E36 328i, are cataloged with different parts. Check the production month on the door label or send us the VIN.
