1966 Corvette: Service News: Corvette Heavy Duty Brakes - Introduction
Subject: Corvette Heavy Duty Brakes
Model and Year: 1966 Corvette with RPO J56 Heavy Duty Brakes
Source: Chevrolet Service News
Page Number: 4
Date: May 1966 - Volume 38 - Number 5
Corvette Heavy Duty Brakes
The brief information below will familiarize the technician with the function and maintenance of the 1966 Corvette Heavy Duty Brakes, RPO J56. These are similar to those used in 1964 and 1965 except for new front wheel caliper assemblies, new brake show and lining assemblies and a rear brake pressure regulator valve. RPO J56 will also be equipped with vacuum power brakes (RPO J50).
FRONT WHEEL CALIPER ASSEMBLIES
The heavy duty front wheel caliper assemblies are similar to the regular production assemblies except for the method of brake shoe retention On the heavy duty assembly, two 5/32 dia. x 3.75 long cotter pins are used, one at each end of the brake show, and on the regular production assembly, one .300 dia. x 3.62 long pin is used in the center of the brake shoe.
BRAKE SHOE AND LINING ASSEMBLIES
The heavy duty brake shoe and lining assemblies differ from the regular production assemblies in that they are bonded rather than riveted and have a high metallic content lining material rather than an organic lining material. If linings are replaced for any reason, special RPO J56 linings must be used. Do not attempt to use regular production lining for replacement. The service part numbers for the RPO J56 shoe and lining assemblies are 5452514 front and 5452515 rear.
REAR BRAKE PRESSURE REGULATOR VALVE OR PROPORTIONING VALVE (SEE FIG. 3)
The rear brake pressure regulator valve, or proportioning valve, is peculiar to the 1966 heavy duty option. The purpose of this valve is to provide balanced braking action between the front and rear brakes under a wide range of braking conditions.
The proportioning valve is factory-adjusted for optimum heavy duty use and no further adjustment should be required. The user may find, however, that different front-to-rear proportioning is desirable under certain conditions. With the large jam nut loosened, turning the large threaded end IN will effectively INCREASE the percentage of rear braking: turning it OUT and DECREASE the percentage of rear braking. Tighten the large jam nut to a torque of 40 to 50 ft. lbs. after making any adjustments. Under no circumstances should the large threaded end be turned more than two (2) full turns in either direction, as this will render the valve inoperative.
Disassembly of the proportioning valve is not recommended: should it fail to perform properly, replace it with the service valve part #3878944.