2-12
GROUP 2-Brakes
FIG.
3—Disc Brake Assembly
splash shield bolted to the spindle
is used primarily to prevent road con-
taminants from contacting the inboard
rotor and lining surfaces. The wheel
provides protection for the outboard
surface of the rotor.
As the brake pedal is depressed,
hydraulic pressure from the master
cylinder forces the piston out of the
bore.
The inboard shoe and lining,
being attached to the piston, is
forced against the rotor. When the
inboard shoe is against the rotor hy-
draulic pressure equalizes and moves
the entire floating caliper assembly
inward. The outboard shoe and lining
assembly attached to the floating
caliper assembly is thereby forced
against the rotor. Hydraulic pressure
forcing the piston-mounted shoe and
lining outward and the caliper-mount-
ed shoe and lining inward creates a
squeezing action against the rotor,
effecting braking action.
During braking action the rubber
boot stretches as the piston moves
outward (Fig. 5). When hydraulic pres-
sure is released the boot relaxes and
pulls the inboard shoe and lining away
from the rotor. When brakes are ap-
plied, hydraulic pressure moves the
floatirg caliper, overcoming the
tension of the stabilizers. When
hydraulic pressure is released, the
stabilizers move the caliper back to
its normal position. Since the outboard
shoe and lining is attached to the
caliper it is moved away from the
rotor. In addition, inherent rotor
CALIPER
HOUSING
PISTON
SHOE
LINING
PISTON
SEAL
FIG.
4—Caliper Assembly—Sectional
View
H
1568-A
PISTON
SEAL
DISTORTED
PISTON
CALIPER
HOUSING
BRAKES APPLIED
FIG.
5—Function of Piston Seal
runout will aid in maintaining run-
ning clearance between the rotor and
the shoe and lining assemblies.
Automatic adjustment is accom-
plished by the piston sliding in the
seal outward from the cylinder
bores.
The piston gradually changes
its position relative to the seal as the
lining wears and, thus, maintains the
correct adjustment location at all
times.
When the brakes are in the unap-
plied position, there is no hydraulic
pressure to the calipers because the
fluid source at the master cylinder by-
passes the residual check valve.
A proportioning valve located be-
tween the pressure differential valve
PISTON
SEAL RELAXED
BRAKES
RELEASED
H
1569-A
and the rear brake wheel cylinders
provides balanced braking action be-
tween the front and the rear brakes
under a wide range of braking condi-
tions (Fig. 7). By regulating the
hydraulic pressure applied to the rear
wheel cylinders, the valve limits rear
braking action when high pressures
are required at the front brakes. In
this manner, premature rear wheel
skid is prevented. The proportioning
valve is serviced as an assembly and
is never adjusted or overhauled.
HYDRAULIC SELF-ADJUSTING
BRAKE SYSTEM
The standard hydraulic brake sys-
tem employs single anchor, internal
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