Farley`s Dodge Diplomat Forum

Forum Index => The Library => Topic started by: Reggie on January 10, 2008, 19:02:32

Title: Brakes: 11.75" Disc Brake Upgrade
Post by: Reggie on January 10, 2008, 19:02:32
Upgrade Your M-Body to 11.75" Disc Brakes

All M-bodies came with 10.87" (AKA 11" per the Factory Service manual) front disc brakes.  The size refers to the diameter of the cast iron hub and disk assemblies (rotors) which are mounted to the spindles. Each rotor has a caliper that straddles it. The caliper is a device that has a hydraulic piston, one inboard pad (or shoe) and one outboard pad. Each caliper is mounted on a sliding assemby called an adapter, so that it can freely move in and out.  As the brake pedal is depressed, brake fuid is forced into a cylinder in the caliper which causes the piston to move the inboard pad against the disc. As the force increases, the entire caliper assembly slides inboard and pulls the outer pad against the disc to provide a clamping force. When the pedal is released, the process is reversed.  The design is self-adjusting.

As far as it is known, no F/J/M-cars came from the factory with 11.75" rotors.  However, many earlier Chrysler products were built with 11.75" rotors. Because the factory bean counters dictated that things got changed only when necessary, it is pretty easy to upgrade an M-body to the 11.75" rotors by finding parts donors with 11.75" rotor caliper adapters. The 11.75" caliper adapters bolt right up to any M-body.

Types of 11.75" Disc Brake Assemblies

There are two types of 11.75" disc brake assemblies used by Chrysler, which require different caliper adapters:

There seems to have been no rhyme or reason to Chrysler's choice of using the pin-type or the slider-type design. Both types were used in many different applications, so it may have been a matter of parts availability among different suppliers. Member "Dr.Jass" recalled that both his 1977 400 HP Cordoba with S13 HD police suspension and his 1979 Chrysler 300 had 11.75" rotors with pin-type calipers. He also had a 1978 400HP Cordoba with 11.75" rotors and slider-type calipers.  Member Reggie (https://www.dippy.org/forum2/index.php?action=pm;sa=send;u=2) bought a 1976 Cordoba 400 parts car that had pin-type calipers.

Either setup uses the same 11.75" rotor, but when swapping larger rotors to an M-body, it's much easier (and cheaper) to just use the slider-type adapters.

Advantages to using the slider-type calipers:

Sources for 11.75" Caliper Adapters:

Additional Parts Needed:

Swap Procedure:

Swap Considerations: