Spec Single Mass Flywheel SAC SB55S – BMW 335i / 435i (F30/F32)

OVERVIEW

SPEC billet flywheels are CNC manufactured on-site to a .001 in. tolerance, against an industry standard of .010 in. That precision gives perfect balance and a perfectly flat bedding surface for the clutch disc, both of which also contribute to safety in competitive environments. All SPEC flywheels carry SFI certification.

The flywheel contributes to power transfer in three ways: it provides a consistent, friction-enhancing surface for the clutch disc; its weight sets the rotating inertia, which controls the ratio of power to acceleration and can make a car quicker or slower depending on gearing, tyre, vehicle weight and where in the powerband the output arrives; and it must run true at rpm, with no dimensional runout to produce vibration. SPEC builds flywheels in high-carbon billet steel and aircraft-quality billet aluminium to cover light and medium-weight options, and can advise on the moment of inertia best suited to a given car. SPEC billet flywheels are developed for specific driving environments and are not a one-fits-all lightweight flywheel — consult a SPEC representative for a recommendation.

SPECS

• Type: single mass billet flywheel
• Material: high-carbon billet steel
• CNC machined to a .001 in. tolerance (industry standard is .010 in.) for a flat clutch bedding surface and true balance at rpm
• SFI certified
• Billet construction — SPEC flywheels are built in high-carbon billet steel and aircraft-quality billet aluminium to suit specific inertia requirements
• Rebuildable, with a replaceable steel friction plate formulated for clutch bedding and holding power (aluminium and most steel units)
• Developed for specific driving environments — not a one-size-fits-all lightweight flywheel
• Clutch compatibility: works with the stock clutch or any stock-design aftermarket self-ratcheting (SAC) pressure plate. It is not an actual dual mass flywheel.
• Not for use with SPEC clutch kits whose part number ends in “-2”.
• Flywheel weight: 26 lbs (SPEC published)

PARTS INCLUDED

• 1x SPEC billet single mass flywheel
• Pressure-plate-to-flywheel bolts
• Complete kit as supplied by SPEC; see the installation instructions for the full bill of materials.

TECH RESOURCES

Additional Parts Required

• None required. This flywheel runs with the stock clutch or a stock-design self-ratcheting (SAC) aftermarket clutch. If you are replacing the clutch at the same time, use a SAC-pattern kit such as SPEC Stage 2+ SB553H.
• Installer-supplied: new flywheel-to-crank bolts (BMW specifies single-use bolts), a flywheel locking tool and a torque wrench.
• When switching to a single mass flywheel some flywheel chatter or rattle is to be expected.

Installation

• SPEC does not publish a downloadable installation PDF for this flywheel — follow the instructions supplied with the flywheel and clutch kit.
• Installation requires removal of the transmission and should be carried out by a qualified technician. Use new flywheel-to-crank bolts and torque to BMW specification.

PART NUMBER

• SB55S

VEHICLE APPLICATIONS