The Wilwood 120-11128 is a four-piston, lug-mount caliper from the Forged Superlite Internal (FSLI) line, built from forged aluminum with a Type III anodized finish. Its four stainless pistons each have a 1.38-inch bore, for a total piston area of 3.00 square inches. Wilwood positions the FSLI series as a direct replacement for Superlite and similar competitive calipers that use 3.50-inch centered mounting tabs, and it targets road-race, off-road, rally, and sport driving alongside short-track and open-wheel use.
Choose this caliper over a stock single-bore unit when you want a multi-piston clamping package for a 0.81-inch rotor. Wilwood's listed rotor width range is 0.75 to 0.84 inches, with a rotor diameter range of 11.75 to 13.06 inches, so measure your disc before ordering. Because the caliper mounts by lugs on a 3.50-inch pattern, it needs a matching bracket and spindle setup rather than factory caliper mounting points. Track-day and sprint-car builders searching for a 4-piston 1.38 caliper for 0.81 rotors, a 3.50 lug mount big brake upgrade, or Wilwood 7420 pad compatibility will find those specs confirmed here.
The manufacturer lists the mount side as universal, so the same caliper is intended for left or right mounting positions. Confirm your bracket and bleed screw orientation during assembly.
The manufacturer lists a nominal rotor width of 0.81 inches, with a minimum of 0.75 inches and a maximum of 0.84 inches. The maximum rotor diameter is 13.06 inches and the minimum is 11.75 inches.
The manufacturer specifies Wilwood pad type 7420, with 8.2 square inches of total pad area and 4.9 cubic inches of pad volume.
The manufacturer recommends Wilwood Hi-Temp 570 or EXP 600 Plus for optimum performance, and EXP 600 Plus for severe braking or sustained high heat. It states that DOT 5 silicone fluid is not recommended for racing or performance driving.
This is a moderate-difficulty job for a home builder with brake experience. Start by mounting the bracket with clean, dry threads, then set shims so the rotor sits centered in the caliper when viewed through the top opening. Confirm hub pattern and wheel clearance before final assembly. Bleed the system starting with the caliper farthest from the master cylinder, working the outboard screw before the inboard. On calipers with four bleed screws, bleed only from the top screws and make sure the bottom screws are tight. If the master cylinder sits below the calipers, a residual pressure valve helps prevent the pedal from sinking on the first stroke. Bench bleed any new master cylinder before installation, check every fitting for leaks afterward, and confirm the pedal feels firm and stops at least an inch above the floor under heavy load. If you have trouble bleeding, consult a qualified brake technician. Tools needed include a wrench set, a torque wrench, a bleed bottle or vacuum pump, shim stock, and lightweight oil for the mounting studs.
