Wilwood Front GM 2500 Hat with Eight-Hole Flange and 12 x 10.75-Inch Rotor Circle

Wilwood's GM 2500 front hat uses a 12 x 10.75-inch rotor circle. Check the 1.550-inch offset, 4.64-inch register and eight-hole hub flange. Bill Wood’s 1977 founding of Wilwood Engineering began a disc brake design and manufacturing business based in Camarillo, California. The range includes master cylinders, calipers, rotors, brake lines, valves and fittings for motorsport, street-performance and specialized vehicles. Component selection must consider the complete braking arrangement.

Technical Details

• Manufacturer part number: 170-8878
• Component: Truck Brake Rotor Hat
• Material: Aluminum
• Surface finish: Black E-Coat
• Rotor mounting method: Fixed Mount
• Position in the specified brake assembly: Front
• Hat offset: 1.550 inch
• Rotor attachment interface: 12 x 10.75 inches; rotor attachment, separate from the hub flange
• Hub-flange mounting/clearance pattern(s): 8 x 6.50 inches; verify the actual hub and wheel-stud clearance
• Center register diameter: 4.64 inches
• Rotor mounting hole/thread designation: 5/16-18
• Internal clearance diameter: 7.85 inches
• Mounting-face thickness: 0.45 inches
• Hub-side hole clearance diameter(s): 0.630 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

Fitment & Compatibility

Match this component to the documented GM 2500 truck brake conversions. Confirm the mounting stack, center location and rotor hardware; vehicle model alone does not establish compatibility with a modified brake system. 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

For fitment assistance backed by more than 20 years of experience, share the installed brake configuration with PMB Performance before ordering.