Four-wheel disc brakes were introduced to the Corvette lineup in 1965. The caliper is fixed to the suspension and split into two sections. Each caliper section holds two floating pistons that push against two brake pads in the front and rear of the car. This GM caliper is a constant contact design, which means the pistons, brake pads, and caliper are always in contact with each other.
This Tech Tip is From the Full Book “HOW TO RESTORE YOUR C3 CORVETTE: 1968-1982“. For a comprehensive guide on this entire subject you can visit this link:
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Each brake piston has a return spring beneath it so it stays in contact with the brake pads. Flexible hydraulic lip seals on each piston slide along the side of the caliper bore to keep the fluid contained in the system. If the brake rotor has excessive run out, it can cause the piston seals to flex and allow air into the brake system.
Rotor runout should be carefully monitored and should not exceed .005, so brake system integrity is maintained. Another point to keep in mind is that excessive rotor runout creates noisy, squeaky brakes. This is caused by the brake pad backing plate moving from side to side and rubbing against the caliper housing and retaining pin.
In 1967 General Motors introduced a second piston design, which was used until the end of the 1982 production year. This cast-aluminum and anodized brake piston is a one piece construction and less prone to admitting air into the braking system.
Two types of brake pads were delivered from the factory. An organic pad was the most common and it was riveted to a steel backing plate and held in place with a single center pin.
The other type of brake pad was designed for competition use and was part of the J-56 competition brake package. This brake pad was a made of a special semimetallic mixture that was bonded to the backing plate. This was later changed to a design that had the pad material molded through the backing plate for better endurance. These pads were held in place with two pins. The rear and the front brake pads used the same friction material and were held in place with a single retaining pin.
Brake calipers manufactured from 1965 to 1971 were cast from ductile iron. The material was strong and had the ability to fl ex without breaking. In 1972 the caliper material was changed to gray iron, which was not as strong and durable as the ductile iron units. When any moisture entered the braking system, both types of calipers were prone to rusting.
The rusting caused the brakes to leak. Today, aftermarket suppliers offer refurbished C3 calipers with stainless-steel inserts to eliminate this issue.
These brakes were fitted to all 1965-1982 Corvettes. That is a lot of cars equipped with this brake design. If your calipers leak, getting a new set of refurbished calipers is an effective way to solve this problem.
Stainless-steel brake lines serve a critical safety function on your Corvette. When you press your foot on the brake pedal you expect your car to stop swiftly and safely. If your brake lines are damaged or rusty and are leaking fluid somewhere in the system you could have a catastrophic brake failure. To avoid this problem, replace all of your existing brake lines with new units. Aftermarket vendors offer pre-bent brake lines to fi t any C3.
There are four flexible brake lines on every C3 Corvette braking system. Two are connected from the hard lines to the calipers in the front and two are connected over the trailing arm bushings in the rear. Original equipment hoses are constructed with an internal rubber line surrounded by woven fiber filler that is covered with a protective rubber jacket. This design has proven itself through many years of successful service. It’s designed to handle high pressure and continuous flexing without failure. It is a good idea to install the lines while the frame is free of suspension and brake components. Take your time and make sure every fitting is secure and the brake line clamps keep the lines from hitting any part of the frame or suspension. Once you have completed this task it is time to move on to the fuel lines.
Step-1: Install Proportioning Valve
Bolt the brass proportioning valve to the frame under the master cylinder. All brake lines are routed through this valve. The system is split for safety reasons. The front and rear brakes work independently of each other so two assemblies continue to function if the other two stop working.
Step-2: Install Brass Rear Junction
The brass junction near the driver-side rear wheel delivers fluid to the passenger side rear brake and has a fitting to connect the driver-side rear brake hose to it. This junction eliminates the need for two brake lines to be routed to the rear of the car for fluid delivery.
Step-3: Install Rubber Brake Line
This is one side of the rear brass brake fluid junction. The rubber brake line is attached to the junction and then routed to the caliper. Screw the brake line into the fitting and make sure it is tight (not just snug) and push the clip into place.
During the C3 evolution from 1968 to 1982 the fuel system underwent subtle changes to address growing environmental concerns. Gasoline vapors were deemed to be hazardous to the environment, and manufacturers were directed to eliminate them. Corvette engineers added a charcoal filter to absorb these vapors, which first appeared in the 1970 model year.
A line runs from the tank on the driver’s side of frame to the canister that is located near the engine. Two fuel lines run from the fuel tank to the fuel pump on the passenger’s side. The larger line feeds the engine and the smaller line returns unburned fuel to the tank. The single fuel vapor line shares space with the brake line on the driver’s side of the frame. The two fuel and return lines are attached to the passenger’s side of the frame.
Follow the same guidelines as when installing the brake line to ensure no lines vibrate against the frame or become kinked in any way. A fuel line rupture could ruin all of your hard work.
All Corvettes produced from 1965 to 1982 came from the factory with four-wheel disc brakes. Power assist (J50) was an option from 1968 to 1976, but from 1977 to 1982, it was standard equipment.
The J56 special heavy-duty brake package was mandatory when ordering Corvettes with the L88 engine option. This robust braking system was only produced in 1968 and 1969, and few cars were so equipped. The cast-iron calipers featured four pistons and were quite effective at stopping a C3 Corvette. Non-powered brakes require a pretty heavy foot to stop the car. Power brakes greatly reduce braking effort and are a worthy option. If your car does not have power brakes, Corvette aftermarket suppliers offer upgrade kits that allow you to convert your car to this much-needed upgrade. The overall braking system design is simple, easy to install, and easy to maintain.
Many aftermarket suppliers offer refurbished C3 brake calipers with stainless-steel inserts. Your old calipers need to be exchanged for these new units; they will be refurbished and resold to another customer. The stainless-steel inserts extend the service life of your braking system, but I strongly advise you to flush the brake fluid every year, particularly if you only drive the car on the weekends. Moisture accumulation is a big enemy of C3 brakes. Annual flushing of the brake system slows this process and helps ensure proper and safe operation of the brake system. It’s very cheap insurance.
Vendors offer a complete front brake set with all of the necessary components. You can also assemble the parts on your own and save some money.
The front brakes are attached to the suspension steering knuckle and secured with two bolts. The front brake calipers are only fitted with one brake fluid bleeder valve. This makes purging the braking system of air a simple process. Do not bleed your brakes until you are close to completing the body/frame installation (see Chapter 12).
Step-1: Inspect Front Brake Kit
This is a complete front brake package that includes calipers, rotors, front wheel bearings, brake pads, new bolts, and brake hoses.
Step-2: Install Front Brake Pads
Before the brake pad is inserted into the caliper, make sure all of the pistons in the caliper are fully retracted into their bores. You might need to use a putty knife or a fl at piece of metal and a screwdriver to push the pistons down into the calipers bores so they are fully retracted. The two brake pads are held in place with one large pin that goes through the caliper and the two brake pads. Once the pads have been secured in place, insert the pin and a cotter key on one end to prevent the pin from backing out. The optional J56 special heavy-duty brake package was fitted to 267 Corvettes in 1968 and 115 in 1969. They were recommended for road racing only. Each caliper was fitted with two pins to hold the pads in place during competition events. The standard single-pin caliper system is a very effective way to stop your Corvette.
This is a refurbished rear 1968 to 1982 brake caliper. It includes stainless-steel sleeves and upgraded pistons and gaskets. Notice that each rear caliper has two bleeder screws that must be cleared of air when the system is being flushed. (The front calipers have one bleeder valve.)
Step-3: Install Cotter Key
Use a needle-nose pliers to correctly bend the cotter key after the pad and caliper have been installed onto the rotor. Installing it this way prevents the pin from causing a rattle, and it does not turn or bind.
Step-4: Install Rotors
Slip the front brake rotors over the lug nut studs on each front steering knuckle and secure them with lug nuts to prevent them from shifting when installing the brake calipers.
Step-5: Attach Brake Hose
Use an open-end wrench to insert a brass washer (front only) between the brake fitting and the caliper. Before mounting the caliper to the front suspension install the brake pads and make sure the brake pistons are fully retracted into the caliper. Push on the pads until they are seated against the inside surface of the caliper. It helps to loosen the bleeder screw before doing this step because you won’t be working against the hydraulic brake pressure that may be behind the pistons.
Step-6: Position Brake Caliper
The brake pistons should be fully retracted in the calipers and the brake pads placed in the caliper. Then the caliper should slip easily over the rotor. Line up the mounting holes on the calipers with the mounting bracket and secure them.
Step-7: Secure Brake Caliper
Two 7/16 x 11⁄8-inch bolts secure each caliper. This is a special bolt size and length. If the bolts are too long they hit the rotor. These bolts are fitted with a 5/8-inch head and need to be torqued to 70 ft-lbs to minimize them working loose during spirited driving.
Step-8: Install Brake Hoses
Attach a flexible brake line to each caliper to force fluid into the pistons. If you’re going to complete an original restoration, use OEM-type hoses even though they expand, crack, and deteriorate over time. Brake performance also deteriorates over time with these hoses. Many owners opt to install steel-braided brake lines because they maintain hydraulic pressure more consistently and don’t stretch and expand like rubber hoses. These lines undergo a lot of stress, and it is always a good idea to install fresh ones when the brake system is rebuilt. These lines should be tightened to 30 ft-lbs to make sure they are tight and leak free.
Step-9: Install Caliper onto Rotor
All four pistons must be all of the way inside the caliper bores before attempting to install the caliper onto the rotor. Slide the retaining pin into the caliper and install the cotter pin. Use a 5/8-inch socket to secure the caliper to the caliper mounting bracket. Torque to 70 ft-lbs.
Step-10: Inspect Caliper and Rotor
This is the completed front brake caliper and rotor that is attached to the front suspension. Once the rear brakes are installed, mount wheels to make it easier to move the frame around your work area.
Rear Parking Brake Assembly
Third-generation Corvettes used a unique parking brake system. It includes a 6-inch-diameter, mechanically actuated drum brake located inside each rear brake rotor. The parking brake handle is located on the center console.
When the handle is pulled to engage the parking brake, it is connected to a spring-loaded cable under the center of the car. Four small brake shoes (two on each side per wheel) expand against the inside of a small drum inside the brake rotor to set the brake.
This parking brake design is very similar to the design of the standard drum brakes on 1963 and 1964 Corvettes. A screwdriver is used to loosen or tighten the pinwheel adjusters for the shoes and adjust the brake shoe travel.
Rebuilding one of these units takes a little patience but they last a long time when the job is done correctly.
Step-1: Install Bolts on Caliper Bracket
Four bolts hold the caliper mounting bracket and the rear bearing support in place. Install these bolts on the inside of the control arm and press them into place.
Step-2: Install Rear Hub Bearing Support
Slide the rear bearing support over the four bolts that were pressed into the trailing arm. Make sure the support is fully seated onto the trailing arm.
Step-3: Install Caliper Mounting Bracket
Place the caliper mounting bracket over the four studs that show through the rear bearing support.
Use a wrench to torque down the four 9/16-inch nuts that secure the rear bearing support and the caliper mounting bracket. Torque these nuts to 40 ft-lbs.
Step-4: Install Backing Plate
The backing plate has two pins, which hold the brake shoes in place. Hold these pins against the underside of the backing plate with tape. Otherwise, the pins could drop while you are trying to secure the brake shoes.
Step-5: Mount Pivot Block
A bolt with a 3/4-inch head holds the pivot block in place. The top of the brake shoes rests on the pivot block, which keeps them from turning inside the drum.
Use an open-end wrench to hold the pivot block in place while tightening the bolt. Torque this bolt to 60 ft-lbs. Use a torque wrench if you don’t have an impact gun.
Use a pair of pliers to bend the locking tabs onto the head of the nut to prevent it from loosening.
Step-6: Install Parking Brake Lever
Insert the parking brake lever into the upper slot on the backing plate. The parking brake levers are stamped “left” and “right.” Make sure to use the correct one for the side you are working on.
Turn the parking brake lever 90 degrees to the right to seat it correctly onto the backing plate. The parking brake cable attaches to this unit to tighten the shoes onto the rear rotor. Attach the cable to the arm as in step 2 on page 120 when the arm is installed into the car.
Step-7: Install Brake Shoes
Slide the previously assembled brake shoes under the pivot arm and feed the pins through the holes in the brake shoes.
A spring and a cupped washer hold the brake shoes in place. Place the washer and spring over the pin and turn the washer 90 degrees to lock it into place.
Place one hooked end of the upper spring into one hole in the shoe. Use a spring hook tool or a slotted screwdriver to stretch the spring far enough to insert the other hooked end into the other hole.
Once the spring has been seated into both holes in the shoe, place a screwdriver behind the spring and push it outward. Make sure the spring is secure and correctly seated in its holes.
Step-8: Install Brake Rotor
Using a hydraulic press, press the axle spindle into the rear bearing support. If you don’t own a hydraulic press, take the spindle and bearing support to a professional shop to have the rear axle spindle pressed on. Here a technician is holding a second axle spindle to show what it looks like unmounted. You need a hydraulic press to insert this part correctly into the bearing support.
Slide the rear brake rotor over the wheel studs. The rotor should slide over the assembly easily unless the brake shoes are out of adjustment. Secure the rotor with two lug nuts.
Step-9: Measure Runout on Rotor
Check the runout on the rotor with a dial indicator. Zero is the ideal reading, but up to .005 is acceptable. Sometimes you can turn the rotor on the axle spindle to improve the readings. Do not put washers between the axle spindle and rotor to correct excessive runout. This quick fix is not a long term solution to a runout problem.
Step-10: Install Parking Brake Shoes
It is possible to install new parking brake shoes with the axle spindle in place. Stretch out the shoes, slide them under the axle spindle, and snug them up against the pivot block.
Step-11: Install Spring and Washer
Carefully pry the shoe away from the axle spindle to provide enough room to install the spring and washer. Repeat this process for the other side. The other end of the spring can be installed after these washers are secure.
The restored parking brake assemblies have been installed onto the refurbished trailing arm. You are now ready to install the complete units with their new rotors onto the frame.
One bolt secures the trailing arms in the front and another bolt fastens both axle shafts in the rear. The rear transverse spring attaches to both sides of the rear trailing arm, and a shock absorber dampens the suspension on each side. The rear brake calipers are attached to the trailing arm with two bolts with 5/8-inch heads that should be torqued to 70 ft-lbs.
Bleeding the Braking System
Every time the brake system is opened, it must be purged of air that has entered into the system. If air is not evacuated from the system, you have a spongy brake pedal. It is more desirable to bleed the longest line first. The normal sequence is: driver side rear inner, driver-side rear outer, passenger-side rear inner, passenger side rear outer, driver-side front and passenger-side front. This method purges the air out of the system. Use a clear container so you can watch the flow of bubbles diminish as the fluid is drained from the system.
Parking Brake Cable
A single lever on the center console actuates the parking brake cable. The cable is routed through the body to a single roller that is mounted to the center of the frame behind the transmission. The other end of the cable has a bracket attached to it that connects to a spring-mounted equalizer mounted on the frame in front of the differential. The cable is routed through a bracket and it holds two parking brake cables that connect to the rear calipers. These two cables are held in place with two brackets that are mounted to each trailing arm. The cables connect to the parking brake lever that operates each parking brake.
Step-1: Install Cable
This is how a completed parking brake cable system looks after it is installed. A piece of string holds the end of the cable that is threaded through the nylon roller. When the body of the car is attached, this end is fed through the floor to the parking brake handle inside the car.
Step-2: Install Catch Ball
A small catch ball is attached to the end of the parking brake cable. Thread the cable under the parking brake lever on the inside of the brake rotor. Notice the parking brake lever is stamped with “LS” for left side.
Step-3: Install Brake Cable Return Spring
The end of the cable has a coil spring to help return the brake lever to the closed position. This spring needs to be secured under the nylon clip on the rear trailing arm.
Step-4: Anchor Parking Brake Cable
Slide the cable bracket into its clip that is also on the rear trailing arm. Secure the bracket with a spring clip (shown).
Completed Rear Brakes and Suspension
The rear brake assemblies are now successfully mounted onto the rear trailing arms and suspension. The frame is ready to have its engine and driveshaft installed prior to installing the refurbished body onto the completed frame.
Written by Walt Thurn and Posted with Permission of CarTechBooks