These all new cast, not rebuilt iron calipers are bolt-on replacements for 1978 and later GM Metric calipers widely used in "spec" racing categories and low cost disc brake conversions. Not IMCA pproved.
Wilwood iron GM Metric calipers combine new part quality with modern machining precision. There are two piston size options to assist builders with properly building static bias into a car. Previously, builders using the metric calipers generally had to mount the same size calipers on all four wheels. This drastically limited the tuning options and often created front to rear bias ratios that were not conducive to good handling and stability under hard braking. Some builders, and other brake suppliers, chose to offer re-machined OE calipers to provide a bias tuning option. Unfortunately re-machining a used casting that was never designed for the larger bore size, can create real compromises in strength, reliability and performance.
To address these needs, Wilwood has tooled up two separate castings that are fitted with either 2.75" or 2" stainless steel pistons and high temperature bore seals. Each casting is designed specific for its intended bore size. The calipers are strong and precise, without unnecessary added weight from oversized castings. The stainless steel pistons resist corrosion while helping to slow the heat transfer from the pads. The high temperature seals provide long service life when used in hard braking applications and maintain their resilience to provide positive piston retraction on release. In addition to the optional piston sizes, two models are available with slide pin vibration dampers installed to help reduce rattle and other noise.
These calipers are the same physical size and mounting as the GM metric style of calipers. Instead of the stock 2-1/2" piston they have either 2" or 2.75" bores. This allows you to change your brake bias on a dirt car by running bigger pistons on the back and small piston on the right front. The bleeder and inlet are both 10mm-1.5 which allows you to run these calipers on either side.
All Wilwood GM Metric calipers use the standard D154 type brake pads.