Spec Clutch SF99A Billet Aluminum Flywheel SFI Certified Rebuildable

The Spec Clutch SF99A is a billet aluminum flywheel CNC-machined to an industry-leading .001 inch tolerance — ten times tighter than the industry standard of .010. This exceptional precision delivers perfect rotational balance and a perfectly flat bedding surface for the clutch disc, maximizing clutch performance and longevity while meeting the safety demands of competitive motorsports environments.

The flywheel body is constructed from aircraft-quality tempered aluminum (6061-T6 or 2024-T3) for ultimate strength at the lowest possible weight. Aluminum flywheels typically weigh roughly half as much as comparable steel units, resulting in faster engine revving, reduced drivetrain drag, and quicker throttle response. A replaceable 1/4-inch thick 1050 high-carbon alloy steel friction plate is secured to the body with aerospace-grade fasteners or stainless steel rivets, providing exceptional durability with any friction disc material. This design makes the SF99A fully rebuildable — when the friction surface wears, only the friction plate needs to be replaced rather than the entire flywheel assembly.

Key Features:

• CNC-machined to a precise .001 inch tolerance — 10× tighter than the industry standard
• Aircraft-quality billet aluminum body (6061-T6 or 2024-T3) for maximum strength-to-weight ratio
• Replaceable 1050 high-carbon alloy steel friction plate for long-term rebuildability
• Aerospace-grade fasteners or stainless steel rivets secure friction plate to the body
• Heat-treated pressed-on ring gear secured with grade-10 fasteners for longevity
• SFI certified — meets the requirements for sanctioned racing and competitive events
• Optimized moment of inertia (MOI) for performance driving and racing applications
• Manufactured in the USA

The flywheel plays a critical role in clutch system performance by providing a consistent friction surface, controlling rotational inertia, and maintaining true balance at RPM to eliminate vibration. SPEC engineers each flywheel application with specific dimensions and weight targets to optimize MOI for the intended use — whether autocross, road racing, drag racing, or high-performance street driving. The SF99A is a precision engineered component developed to complement SPEC clutch kits and maximize overall drivetrain efficiency.