The Wilwood 120-11133 is a four-piston Forged Superlite Internal (FSLI) caliper with 1.62-inch pistons, sized for 1.25-inch rotors and finished in Type III anodize. Wilwood positions the Superlite family as a benchmark for short track, late model, modified and open-wheel competition, and the line also serves road-race, rally, off-road and sport driving builds. Its stainless pistons total 4.12 square inches of piston area, so this is a practical choice for a 1.25-inch rotor track car or a 1.62-inch piston brake upgrade.
The case for this caliper over a generic unit comes down to fitment and pad supply. The manufacturer describes the FSLI as a direct replacement for Superlite and similar competitive calipers with 3.50-inch centered mounting tabs, so a builder already running that mount pattern can upgrade without fabricating new brackets. It uses the 7420-type bridge-bolt pad that the manufacturer says is shared across all Superlite six-piston calipers, which keeps pad sourcing within a familiar family.
Installation is a bracket-and-bleed job. The manufacturer's install sheets call for mounting the caliper with the bleed screws pointing up, using shims between caliper and bracket to center the rotor, and bleeding from the caliper farthest from the master cylinder. Wilwood recommends an external residual pressure valve when the master cylinder sits below the calipers, and specifies EXP 600 Plus fluid for severe braking. Owners on user forums report bleeder screws snapping when over-tightened, so bleed carefully from the top bleeder.
The manufacturer states the FSLI is a direct replacement for Wilwood Superlite and similar competitive calipers with 3.50-inch centered mounting tabs. Confirm your bracket's mount center and rotor width before ordering.
Per the manufacturer, this caliper uses the 7420-type bridge-bolt pad, the same pad used across the Superlite six-piston calipers.
Owners on user forums report that bleeder screws can break when tightened, and one recommended removing the caliper and using an easy-out to extract a broken screw while keeping metal shavings out of the bore.
Plan on a moderate DIY job that rewards patience. Bench-bleed the master cylinder before installation, since owners on user forums report that bench bleeding alone does not always clear all air, so finish bleeding with the master cylinder on the car. Mount the caliper with bleed screws up, shim for rotor centering, and torque the mounting hardware per the manufacturer's install sheet. Avoid DOT 5 silicone fluid for performance driving, and flush with fresh racing fluid as the manufacturer recommends.
