Wilwood Front Rotor Adapter for Mustang Four-Lug Brake Conversions (1965–1966)

This Wilwood Mustang rotor adapter joins a six-bolt ring to the dedicated hub. Confirm its disputed offset before ordering; it is not a wheel hub. Wilwood Engineering, founded in 1977 by Bill Wood, is based in Camarillo, California. The company designs and manufactures disc brake systems and supplies master cylinders, calipers, brake rotors, valves, fittings and lines for motorsport, street-performance and specialized installations. Select each component around the complete system’s requirements.

Technical Details

• Manufacturer part number: 170-12538
• Internal clearance diameter: 5.20 inches
• Mounting-face thickness: 0.32 inches
• Hub-side hole clearance diameter(s): 0.390 inches; these are clearance dimensions, not wheel-stud thread sizes
• Manufacturer-listed attachment hardware reference: 230-12176; verify the specific rotor and attachment arrangement before ordering hardware
• Component: Rotor-Mounting Adapter
• Material: Aluminum
• Surface finish: Black E-Coat
• Rotor mounting method: Fixed Mount
• Position in the specified brake assembly: Front
• Hat/adapter offset: 0.750 inch on the product page; 1.07 inches in DS921. Confirm the supplied dimension and measurement reference with Wilwood.
• Rotor attachment interface: 6 x 6.25 inches; rotor attachment, separate from the hub flange
• Hub-adapter attachment circle: 5 x 3.35 inches as listed in the product catalog; this fastens the rotor adapter to the hub and is not the vehicle wheel pattern
• Center register diameter: 2.75 inches
• Rotor mounting hole/thread designation: 5/16-18

Fitment & Compatibility

This rotor-mounting adapter is used with the dedicated hub in Wilwood’s 1965–1966 four-lug Mustang front conversion, documented in DS921. Its five-hole adapter connection is not the vehicle’s four-lug wheel pattern. Wilwood gives 0.750-inch offset on the product page and 1.07 inches in DS921. Confirm the supplied adapter and dimensional reference before ordering; no equivalence between the measurements is assumed.

Manufacturer Reference

Wilwood component specifications and dimensions · Assembly instructions DS921

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