The Wilwood 120-9703 is a forged billet DynaPro lug-mount caliper with four stainless pistons, each 1.38" in diameter. The manufacturer presents the DynaPro Lug Mount as its newest generation of calipers, meant to upgrade or replace applications that used the older Dynalite series. Owners on user forums point to rebuildability as the durability advantage: a full rebuild can renew nearly every serviceable part, while a lighter refresh only needs the main seals and cross-over seals replaced, reusing the pistons and bleed valves. That makes this caliper a practical long-term choice for track and autocross builds.
Fitment centers on the 5.25" lug pattern and a 0.81" rotor. The manufacturer lists a 5.25" lug mount with 1.38" pistons and a maximum rotor diameter of 13.06". This part number is the black finish; the manufacturer also offers a red (-RD) and an anodized (-SI) variant. Because the pistons have no dust boot, owners who run the caliper hard tend to choose stainless pistons for their corrosion and heat resistance. Searchers looking for a 5.25 lug mount big brake caliper, a Dynalite replacement, or a 4-piston 1.38 stainless caliper rebuild will find this part fits that profile.
The manufacturer describes the DynaPro Lug Mount as an upgrade or replacement for applications that previously used the Dynalite series. Confirm the bolt pattern, rotor width, and hose fitting against your current caliper before ordering.
Owners on user forums report rebuilding these calipers with new seals, stainless pistons, and M10 x 1.0 tapered-seat bleeder valves. A full rebuild typically replaces most serviceable hardware, while a basic refresh only requires new main and cross-over seals.
Owners who rebuild these calipers generally plan for four pistons per caliper and bleeder valves with an M10 x 1.0 tapered seat, so pick up those parts before tearing the caliper down. Owner write-ups describe the rebuild as straightforward for a home mechanic, but torque values and installation difficulty were not confirmed on the manufacturer's own documentation. Check the manufacturer's install sheet for torque specs, and bleed the brake system thoroughly after installation before driving.
