Abstract: The disc brake disclosed is of the type used for heavy equipment, including off-the-road vehicles. It is oil cooled, with the disc pack being enclosed in a housing. In brakes of this type which are currently on the market, the wear of the disc pack can be checked only by disassembly of the brake assembly. The disclosure shows an arrangement wherein pack wear can be checked without requiring such disassembly. The bosses in which piston retracting mechanisms are provided are convenient for such purposes. One or more of these bosses is provided with a tapped access hole after having the boss end surface machined to a smooth finish. When the brake disc pack is new, the service brake piston and the parking brake release piston cavities are pressurized, causing the parking brake piston to back off completely. The service brake piston squeezes the disc pack against the parking brake piston and pulls the service brake piston return spring guide pins with it.

Abstract: An annular type disc brake assembly having parking brake apply springs which are pre-loaded is arranged for disassembly in such a manner that the load on the parking brake springs must be evenly released in small increments until there is no pre-load on the springs. This is accomplished by providing several of the securing bolts assembling the housing section containing the spring to another housing section of a different, longer length than the remaining securing bolts of this type. The longer bolts are arranged so that they can be moved translationally into position in the one housing section before assembly and have at least a portion of the bolt heads then covered by slotted safety lugs formed as a part of the one housing section. When the disc brake is to be disassembled, the shorter bolts are first removed, leaving only the longer bolts to hold the housing sections together and resist the force of the parking brake apply springs.

Abstract: A disc brake service piston for heavy equipment and off-the-road vehicles has an annular configuration and is sealingly and reciprocably received in an annular cavity forming a pressure chamber. During brake disassembly requiring removal of the piston from the cavity, the piston must be disconnected from a series of piston retracting mechanisms. The arrangement permits the force of one piston retraction spring to be relieved at a time. A tool is used which has a thread at one end and a handle at the other end. The threaded end is inserted into a tapped hole at the end of a return spring guide pin which transmits the spring force of one retracting mechanism to the piston. The tool can then be moved to compress the guide pin spring so that the pin is moved a sufficient distance to expose a cross pin therein which provides the connection between the guide pin and the piston. The cross pins are removed, one by one, from all of the spring guide pins of all of the mechanisms.