Wilwood Front Flared-Bell Hat for Large GM Drop-Spindle Conversions

This Wilwood GM drop-spindle hat uses a flared bell and 1.200-inch offset. Check the separate rotor attachment and hub anchoring hardware. Bill Wood founded Wilwood Engineering in 1977, and the manufacturer is based in Camarillo, California. Wilwood designs and manufactures disc brake systems alongside calipers, master cylinders, rotors, fittings, brake lines and valves. The motorsport, street-performance and specialized ranges depend on components selected to work within a complete braking system.

Technical Details

• Manufacturer part number: 170-10231
• Mounting-face thickness: 0.25 inches
• Hub-side hole clearance diameter(s): 0.520 inches; these are clearance dimensions, not wheel-stud thread sizes
• Manufacturer-listed attachment hardware reference: 230-8008; verify the specific rotor and attachment arrangement before ordering hardware
• Manufacturer installation note: Hat is drilled and countersunk in three places to accommodate hat to hub anchoring screws used with specific Wilwood hat mount hubs. Use 230-7032 (contains 6 qty. 1/4-20 x .50 Flat Head Hex Drive mounting screws)
• Component: Flared-Bell Brake Rotor Hat
• Material: Aluminum
• Surface finish: Black E-Coat
• Rotor mounting method: Fixed Mount
• Position in the specified brake assembly: Front
• Hat offset: 1.200 inch
• Rotor attachment interface: 12 x 8.75 inches; rotor attachment, separate from the hub flange
• Hub-flange mounting/clearance pattern(s): 5 x 4.50, 5 x 4.75 inches; verify the actual hub and wheel-stud clearance
• Center register diameter: 3.06 inches
• Rotor mounting hole/thread designation: 1/4-20
• Internal clearance diameter: 6.86 inches

Fitment & Compatibility

For Large GM drop-spindle brake conversions, compare the replacement with the actual hat and complete brake-kit instructions. A matching flange pattern alone does not establish rotor alignment or caliper clearance. Select the rotor and attachment hardware separately for the documented assembly. Follow the installation drawing for engagement and clearance at every mounting point.

Manufacturer Reference

Wilwood component specifications and dimensions

PMB Performance brings over 20 years of experience to brake-component selection. Provide the actual hardware specification when the brake system has been modified.