Jeep Cherokee 2000, Service Manual

Page: 175 / 1528

In summary, fluid pressure acting simultaneously
on both piston and caliper, produces a strong clamp-
ing action. When sufficient force is applied, friction
will attempt to stop the rotors from turning and
bring the vehicle to a stop.
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 brake shoes 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. 3).
When the brakes (and fluid pressure) are released,
the seal relaxes and retracts the piston.
The amount of piston retraction is determined by
the amount of seal deflection. Generally the amount
is just enough to maintain contact between the pis-
ton and inboard brake shoe.
REAR DRUM BRAKE
DESCRIPTION
The rear brakes use a leading shoe (primary) and
trailing shoe (secondary) design (Fig. 4).
OPERATION
When the brake pedal is depressed hydraulic pres-
sure pushes the rear brake wheel cylinder pistons
outward. The wheel cylinder push rods then push the
brake shoes outward against the brake drum. When
the brake pedal is released return springs attached
to the brake shoes pull the shoes back to there orig-
inal position.
PARKING BRAKE
DESCRIPTION
The parking bake is a hand lever and cable oper-
ated system used to apply the rear brakes.
OPERATION
A hand operated lever in the passenger compart-
ment is the main application device. The front cable
is connected between the hand lever and the ten-
sioner. The tensioner rod is attached to the equalizer
which is the connecting point for the rear cables (Fig.
5).
The rear cables are connected to the actuating
lever on each secondary brake shoe. The levers are
attached to the brake shoes by a pin either pressed
into, or welded to the lever. A clip is used to secure
the pin in the brake shoe. The pin allows each lever
to pivot independently of the brake shoe.
To apply the parking brakes, the hand lever is
pulled upward. This pulls the rear brake shoe actu-
Fig. 2 Brake Caliper Operation
1 – CALIPER
2 – PISTON
3 – PISTON BORE
4 – SEAL
5 – INBOARD SHOE
6 – OUTBOARD SHOE
Fig. 3 Lining Wear Compensation By Piston Seal
1 – PISTON
2 – CYLINDER BORE
3 – PISTON SEAL BRAKE PRESSURE OFF
4 – CALIPER HOUSING
5 – DUST BOOT
6 – PISTON SEAL BRAKE PRESSURE ON
XJ
BRAKES 5 - 5
DESCRIPTION AND OPERATION (Continued)