The Wilwood 120-13839-BK is a black Forged Dynalite Internal four-piston caliper with a forged aluminum body, 1.38 bore pistons, and a 0.81 rotor width. The manufacturer says the forging process re-aligns the metal's grain structure within the contour of the caliper body, and its radial transition design substantially increases resistance to deflection and caliper separation under load. For a buyer, that structural margin is the main reason to pay for this over a stock caliper or a cheaper cast unit. Structural deflection and volume displacement tests have proven the Forged Dynalite to outperform all existing styles of this popular caliper size.
The pad platform is the 7112 type, which the manufacturer says is the same pad used in all earlier versions of this caliper, so pad choice stays wide open. Wilwood lists PolyMatrix compounds for this pad family, and a factory 7112 pad set is available as BP-10. Fitment is a universal left/right mount: the manufacturer describes the caliper as a direct replacement for all Wilwood Dynalite and similar competitive brand calipers with 5.25" centered mounting lugs. Confirm your bracket and rotor match before ordering. Owners on user forums recommend cleaning the pistons before pad installation, and note that the pistons can drag if the caliper sits in damp conditions. Plan for a steel-line setup, because the 1/8-27 NPT inlet means OEM rubber brake hoses generally cannot be adapted to Wilwood calipers.
The manufacturer lists this Forged Dynalite as a universal application with a 5.25-inch centered lug mount, so it is not built for a single vehicle. Check your spindle or bracket spacing and the rotor width (0.81 in) before ordering.
The manufacturer specifies the 7112 pad type. It lists a BP-10 pad set (part number 150-8850K) for the Forged Dynalite family, and other 7112 compounds are available.
The manufacturer's assembly instructions state that OEM rubber hoses generally cannot be adapted to Wilwood calipers. Use steel adapter fittings at the 1/8-27 NPT inlet and steel-braided line.
The manufacturer's kit instructions call for filling and bleeding the system with Wilwood Hi-Temp 570 fluid or higher, and they recommend bleeding from the caliper farthest from the master cylinder. Use red thread-locker on the mounting bolts and torque them to your bracket's specification, and safety-wire them if your kit calls for it. Apply the thread-locker and torque to the bolts before you bed in the pads. Owners on user forums suggest cleaning the pistons before installing new pads and checking for drag after the caliper has sat in damp conditions.
