GMA Wagner Rear Master Cylinder 5/8 Bore For Harley-Davidson FL FX 1958-1979

GMA Wagner Rear Master Cylinder 5/8 Bore For Harley-Davidson FL FX 1958-1979

Upgrade your vintage Harley-Davidson’s braking performance with the GMA Wagner Rear Master Cylinder. Specifically engineered for classic Shovelhead and Panhead models, this master cylinder features the highly sought-after 5/8″ bore size. This specific diameter provides the necessary hydraulic leverage required for most aftermarket multi-piston brake setups, ensuring a firm and responsive pedal feel compared to standard OEM units.

Constructed with precision in the U.S.A., these Wagner-style cylinders utilize offset 3/8″ mounting holes designed for seamless integration with original frames and custom builds alike. Whether you are restoring a Duo Glide or building a custom Low Rider, GMA provides the reliability and finish quality demanded by professional builders.

Technical Specifications

• Bore Size: 5/8″
• Mounting Holes: 3/8″ offset at 2.25″ on centers
• Inlet Size: 1/8-27 NPT
• Dimensions: 4-1/16″ L x 1-7/16″ W x 2-7/8″ H
• Fluid Type: D.O.T. 5 Silicone Brake Fluid
• Country of Origin: Made in the U.S.A.

Key Features

• Enhanced Braking: The 5/8″ bore is the industry standard for powering aftermarket multi-piston calipers.
• Direct Replacement: Designed to replace Wagner-style master cylinders with the classic offset mounting pattern.
• Premium Finishes: Available in Natural, Polished, or Black to match your motorcycle’s aesthetic.
• Durable Construction: Heavy-duty internals for long-term reliability in vintage applications.

Installation and Fitment Notes

• Fluid Warning: Use ONLY D.O.T. 5 brake fluid. Mixing with D.O.T. 3 or 4 will cause seal failure.
• Late 1979 Models: Harley-Davidson transitioned master cylinder styles in 1979. This unit fits “Early” 1979 models using the Wagner-style mount.
• Check Clearance: Ensure 2.25″ center-to-center spacing on your mounting bracket before ordering.