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Product details
The 7.09-inch radial attachment distinguishes this right Wilwood GN4R-ST brake caliper. This individual anodized unit is built for the 1.25-inch-wide rotor configuration and requires accurate alignment with the mating rotor and bracket. Grand National GN4R-ST is a forged four-piston radial caliper with Thermlock insulated pistons. Its special bracket offset and 7520 pad outline require a measured brake assembly. Use the exact nominal rotor width below rather than a general family-width assumption. Calipers, brake rotors, master cylinders, valves, fittings and brake lines are among the disc brake components designed and manufactured by Wilwood Engineering. Bill Wood founded the company in 1977; it is based in Camarillo, California. The range serves motorsport, street-performance and specialized systems, with component selection determined by the full brake arrangement.
Technical Details
- Manufacturer part number: 120-16528
- Component: Grand National GN4R; one individual caliper
- Placement: Right
- Construction and finish: Forged aluminum; Type III Anodize
- Pistons: 4; Thermlock insulated; bore dimensions 1.88/1.75 inches
- Hydraulic piston area: 5.18 square inches
- Dust boots: No
- Brake pad shape: 7520; shape number does not specify a friction compound
- Nominal rotor width: 1.25 inches
- Rotor width range: 1.19–1.25 inches
- Rotor diameter range: 12.19–14.00 inches
- Caliper weight reference: 8.0 lb
- Mounting interface: Radial; mounting centers 7.09 inches
- Mounting-hole diameter: 0.45 inches
- Mount height: 2.33 inches
- Hydraulic inlet thread: 1/8-27 NPT
Fitment & Compatibility
Match the 7.09-inch radial attachment to the existing bracket, then check caliper centering over the 1.25-inch nominal-width rotor. Use the right-hand caliper and keep the bleed arrangement in the specified orientation. The 1/8-27 NPT connection must use the correct fitting and seal. Check the full wheel envelope with the actual bracket and rotor installed.
Wilwood caliper specifications
Contact PMB Performance for a component comparison using the actual caliper, bracket and rotor measurements. Our team has over 20 years of experience with parts and fitment details.
