Safety is the single most important factor when undertaking any modification project. Any changes should be carefully studied to see how the modification will effect other components. The planed modification itself must be looked at closely to see if it and the components used are safe. When adding power assist brakes to an existing system, it is strongly recommended that you rebuild or replace all wheel brake cylinders. The increased pressures of power assist on old or weak components could cause brake failure.
There are several kits available for the various early trucks. These kits cover each production range from 1928 - 1940, 1941- 1955 1st and 1955 2nd - 1959. Usually these kits are offered in BASIC or COMPLETE kits. The Basic Kit contains caliper brackets and all the hardware for mounting the caliper to the axle. These kits also include bearing adapters and spacers for adapting the new rotors to the original spindles. The Complete Kit contains all the items found in the Basic Kit along with new rotors, calipers, seals and bearing caps. In most cases the calipers are rebuilds. Some Complete Kits offer redesigned hubs. The redesigned hub mounts directly on the original spindles, which eliminates the need for the spindle to bearing adapters. Golden State Pickup Parts now offers a 6 lug brake kit in both Basic and Complete form. The 6 lug kit allows you to use the stock wheels in most cases.
These kits can be purchased from most all of the classic truck specialty parts suppliers. Prices between kits varies depending on the kit selected and supplying vendor. The Basic Kits start around $125.00 and up. The Complete Kits start at $385.00 and up. There are some advantages to purchasing the kits in one form or another.
The Basic Kit will save you the cost of purchasing new rotors and calipers and the cost of having them ship to you. Junk yard parts usually provide a better valve. I have found trucks with almost new brakes on them in the junk yard, so don’t discount used brake components.
The Complete Kits offer some advantages over the Basic Kit. One of the advantages is the new rotors can be ordered with whatever bolt pattern you might need to match your rear end or existing wheels. For a stock look, you may what to purchase a six hole rotor to fit an original wheel. New rotors and calipers offer a degree of assurance of operation over junk yard parts, but not really enough to talk about.
No matter which kit you purchase there are many other parts you will need to purchase before you have a functioning brake system.
GET YOUR WALLET OUT
The next bit of information is basic to any brake system upgrade that incorporates front disc brakes. You will need to purchase the following items.
10 lb. Residual Check Valve.
Brake Line & Fittings.
Now, there are a few different ways to setup the power booster and master cylinder. One arrangement lets you mount a booster and master cylinder assembly under the floor of the cab in the original location. The next method is to mount the booster and master cylinder assembly on the engine side of the firewall, above the steering column. The last method, which I prefer over the rest, is a remote booster under the cab and the master cylinder mounted on the fire wall. I prefer this method, because is utilizes a swing type brake pedal over the booster and master cylinder assembly mounted in the original location and it uses the least amount of under hood space. I also hate pulling up carpet, sill moldings and floor plugs to ckeck the brake fluid, so the firewall mounted systems are my first choice.
For the reasons stated above, the remote booster brake system was my choice for this project. The follow is a description of its installation. The graphic below shows a component diagram of the remote booster brake system. We'll get into the function of each component as we go along.
PHOTO HERE - Remote Booster System
Most hobbyist are familiar with the operations of the master cylinder and vacuum brake booster. So, well dispense with the basics. You may not have dealt with residual check valves and adjustable proportioning valves though. So, we will take a moment to cover these components.
Proportioning ValveThe residual check valve is a component that is in most all brake systems, but usually not as separate component. In most systems the residual check valve(s) are built into the master cylinder. It’s purpose is to keep enough residual fluid pressure on the brake shoes to maintain a minimal clearance between the shoes and drums/rotors. This is done by checking the direction of the brake fluid at a design pressure. This checking action of the valve maintains a pre-set fluid pressure on the wheel cylinders, thus maintaining proper brake clearances.
On drum/disc combinations, the needed residual pressures will differ. To allow for this factor, a 10 lb. residual check valve is added to the main line supplying the drum brakes. Disc brakes, usually, do not require residual pressure to maintain shoe to rotor clearances. The exception is when the booster is lower or at the same level of the calipers. It maybe necessary to add a 2 lb. check to the main supply line feeding the discs.
Proportioning ValveThe proportioning valve is also another component of most brake systems. On most production vehicles, the valve is pre-set and not adjustable. This valve is sometimes mistaken for a junction block for brake lines. No matter what type of brake system you have, a proportioning will be part of the configuration.
Simply enough, the proportioning valve provides for pressure control of brake fluid. Control of these pressures allows for balancing of the front and rear brakes. A vehicles weight distribution and type of brake system determine the valves setting. When you change the vehicles weight, change the center gravity or add front disc brakes, an adjustable proportioning valve is just the ticket to balancing it all out.
With all the engineering theory out of the way, let's get down to the project. I would also like to say that I will not be relaying common sense safety procedures, so read on at your own risk. Remember that stand jacks are always optional for the dead and a requirement for all others.
Since the brake system was to be replaced as part of the whole restoration project, I junk the whole thing except for the rear brake hose bracket, spindle nuts and outside bearing retaining washers. If your doing this on a running truck, strip the front axle of the old drums and backing plates. Remove the flexible brake line and bracket as well. Now you should be down to the bare spindle.
BUILDING THE SPINDLE
Caliper BracketStart the installation by attaching the new caliper backing plates to the spindle. I had to remove a little material on the caliper brackets at the location shown in the photo to get them to fit properly. A little trimming is usually the case with most universal kits, so don’t be concerned when it happens to you. I used a die grinder and file to remove the material need make the brackets fit correctly. After all the trimming and fitting was completed, I removed the brackets, painted them and chased the caliper bolt holes. After painting, bolt the new plates on to the spindle with grade eight bolts. Use grade eight castellated or nylon bushed retaining nuts with cotter pins.
Next, clean off the spindle with a emery cloth or fine shop roll material. The spindle must not only be clean, but polished to a fine Finish. The fit of the adapter is very tight, so take the time Bearing Adapternecessary to do a good job. Drive the bearing adapter on to the spindle to the position shown in this photo. The adapter must fit flush with the back of the spindle. Use a piece of 1 ½" Schedule 80 PVC pipe to drive the adapter on to the spindle. Once it’s on, only a press can remove it. In some cases the rear bearing area might have had some damage and the adapter will not fit tight on the spindle. If the rear bearing area is only slightly worn, then use a center punch to raise the bearing surface. Be careful not to get carried away, one raised point every 90 degrees is sufficient. In cases where the wear is too great, replace the spindle.
Next, install the new races in rotor hub and pack the new roller bearings. Set the rear bearing into the rotor hub and install the bearing seal. Place the rotor onto the spindle and install the outer bearing, bearing retaining Rotorwasher, spacing washer and spindle nut. Don’t forget the cotter pin, then install the bearing cap. The bearing retaining washer and spindle nuts are the only parts saved from the original setup. The spacing washer is supplied in the kit (shown here) and is used to space the spindle nut out from the rotor hub to line up with the existing cotter pin hole.
SETTING THE CALIPERS
Now that both rotors have been mounted to the spindles, its time to set the calipers. Test fit the caliper onto the rotor without the brake pads. Fit one side at a time. Slip the retaining bolts into position and tighten them down. Assuming the vehicle is on jacks, move the steering from one end to the other. Check for obstructions. I had to trim some casting flashing from the caliper hose fitting area. The photo shows the area where the flashing was removed. Take time to fit the calipers to each side to clear any obstructions. The old spindle stops will not work with the new caliper brackets, so they will have to be removed. I double nutted the king pin retaining pin to provide a spindle stop.
Complete BrakeAfter the fitting is complete, install the brake pads and remount the calipers. You will have to determine the hose length that fits you application best. Connect the flexible brake hose to its original fitting. You can have brake hoses made up at almost any parts supplier. On the project truck, I have installed a set of donor brackets from a 1980 El Camino. I also pulled the calipers and rotors off the same vehicles. If I had choose to mount these hoses at the original connection, the hoses would be too short.
MOUNTING THE BOOSTER
The next section covers power booster and master cylinder connections. The connection information in this section will be covered in general. I’ll be using the remote booster system as the example.
The old master cylinder is removed, leaving a front and rear brake supply line. Once the booster is in place, a tee is used to connect both lines together. A main feed line is tied into the tee from the booster to complete the supply line plumbing. If you are using a dual reservoir master cylinder/booster mounted under the cab floor in the OEM location or on the firewall, extend and connect each line to the appropriate reservoir port on the master cylinder.
Now to add the proportioning valve and residual pressure check valves. On the supply line for the rear brakes, about 8" down from the tee, the proportioning valve is cut in. This will help us even out the braking on the project truck. Down the same line another 6", a residual pressure check valve is cut in. As shown in the photo, the red RPCV will maintain 10 lb. of residual brake fluid pressure on the rear brake wheel cylinders.
All that is left in this project is the placement and mounting of the master cylinder to the firewall. This project is covered in your brake swing pedal article, don't miss it. - CTS