Front Disc Brakes; Master Cylinder; Rear Disc Brakes - Jeep 1996 Grand Cherokee Service Manual

5 - 4 BRAKES
DESCRIPTION AND OPERATION (Continued)
Fig. 2 Master Cylinder
pressure in the separate front/rear brake hydraulic
circuits.
A decrease or loss of fluid pressure in either
hydraulic circuit will cause the switch valve to shut-
tle to the low pressure side. Movement of the valve
pushes the switch plunger upward. This action closes
the switch internal contacts completing the electrical
circuit to the red warning light. The switch valve will
remain in an actuated position until repairs are
made.
The rear proportioning valve is used to balance
front-rear brake action. The valve allows normal
fluid flow during moderate effort brake stops. The
valve only controls (meters) fluid flow during high
effort brake stops.

FRONT DISC BRAKES

The calipers are a single piston type. The calipers
are free to slide laterally, this allows continuous com-
pensation for lining wear.
When the brake are applied fluid pressure is
exerted against the caliper piston. The fluid pressure
is exerted equally and in all directions. This means
pressure exerted against the caliper piston and
within the caliper bore will be equal (Fig. 3).
Fluid pressure applied to the piston is transmitted
directly to the inboard brakeshoe. This forces the
shoe lining against the inner surface of the disc
brake rotor. At the same time, fluid pressure within
the piston bore forces the caliper to slide inward on
the mounting bolts. This action brings the outboard
brakeshoe lining into contact with the outer surface
of the disc brake rotor.
In summary, fluid pressure acting simultaneously
on both piston and caliper, produces a strong clamp-
ing action. When sufficient force is applied, friction
will stop the rotors from turning and bring the vehi-
cle to a stop.
Fig. 3 Brake Caliper Operation
Application and release of the brake pedal gener-
ates only a very slight movement of the caliper and
piston. Upon release of the pedal, the caliper and pis-
ton return to a rest position. The brakeshoes do not
retract an appreciable distance from the rotor. In
fact, clearance is usually at, or close to zero. The rea-
sons for this are to keep road debris from getting
between the rotor and lining and in wiping the rotor
surface clear each revolution.
The caliper piston seal controls the amount of pis-
ton extension needed to compensate for normal lining
wear.
During brake application, the seal is deflected out-
ward by fluid pressure and piston movement (Fig. 4).
When the brakes (and fluid pressure) are released,
the seal relaxes and retracts the piston.
The amount of piston retraction is determined by
brakelining wear. Generally the amount is just
enough to maintain contact between the piston and
inboard brakeshoe.

REAR DISC BRAKES

Rear disc brake components consist of single pis-
ton, floating-type, rear disc brake calipers and solid
rotors.
The rear calipers are mounted in a bracket
attached to the rear axle tube flange (Fig. 5). The
calipers are secured to the bracket with mounting
bolts. The bracket also secures the rear disc brake
rotor splash shield to the tube flange.
The rotor and splash shield used for rear disc
brake applications are unique. The parking brake-
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