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 Disc
Brake Conversation
1928 - 1959 Chevrolet / GMC
<BACK TO PAGE ONE
THE COMPONENTS
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.
 The
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.
 The
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.
GETTING STARTED
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
 Start
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  necessary
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  washer,
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.  [more]
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