Spec Clutch SD84A Billet Aluminum Flywheel SFI Certified

The SPEC SD84A Billet Aluminum Flywheel is a precision-engineered, SFI-certified performance flywheel built for demanding street and competition use. SPEC flywheels are CNC-machined to an industry-leading .001-inch tolerance — ten times tighter than the industry-standard .010 — delivering perfect rotational balance and a flawlessly flat bedding surface for consistent clutch disc engagement.

Constructed from aircraft-quality billet aluminum, the SD84A significantly reduces rotating mass compared to a stock cast iron flywheel, allowing the engine to rev faster and deliver peak power more efficiently. The aluminum body is paired with a replaceable 1/4-inch thick 1050 high-carbon alloy steel friction plate, specially formulated for optimum clutch bedding and holding power, and compatible with virtually any friction disc material including iron.

Key Features:

• CNC-machined to .001-inch tolerance for perfect balance and zero dimensional runout
• Aircraft-quality billet aluminum construction — 6061-T6 or 2024-T3 tempered aluminum
• Replaceable 1050 high-carbon alloy steel friction plate for rebuildability and long service life
• Friction plate secured with aerospace-grade fasteners or stainless steel rivets
• Heat-treated, pressed-on ring gear secured with Grade 10 fasteners
• SFI certified — meets safety requirements for sanctioned racing and competitive environments
• Engineered for optimized Moment of Inertia (MOI) to maximize power transfer and acceleration
• Designed, hand-built, and tested in the USA

The flywheel plays a critical role in clutch performance and longevity. It must provide a consistent friction surface, supply the correct rotational inertia for the application, and maintain true balance at all engine speeds to eliminate vibration and power loss. SPEC engineers each flywheel with application-specific dimensions and weight targets to optimize MOI for the intended driving environment — whether autocross, drag racing, road racing, or spirited street use.

The rebuildable design of the SD84A makes it a long-term investment: when the friction surface wears, simply replace the steel friction plate rather than the entire flywheel assembly.