Chapter 12 Disc Brake System Components and Operation 201
Figure 12-17. A four-piston, fixed caliper brake assembly. A—Overall view of the one-piece caliper. B—Cross-sectional view
showing the internal parts. (Kelsey-Hayes)
One-piece
fixed caliper
Hub
Ventilated
rotor
Splash
shield
Transfer
tube
Transfer
tube
Rotor
Square cut
O-ring
seal
Piston
Boot
Pad and
plate
Adapter plate
Caliper
Figure 12-18. A—This shows the seal being bent outward as hydraulic pressure forces the piston out of its bore. B—Here the
square-cut seal is in a normal resting position and shape after the piston has returned. (Chrysler)
Piston
Cylinder
bore
Piston seal brake
pressure off
Caliper
housing
Dust boot
Piston seal brake
pressure on
A
B
B A
Fixed Caliper Operation
When the brakes are applied, hydraulic pressure
enters the caliper assembly, Figure 12-18. Pressure flows
through internal passages or external transfer tubes, pres-
surizing all four pistons at the same time. The pistons move
outward, forcing the brake pads into contact with the spin-
ning rotor, slowing or completely stopping it. When the
brakes are released, hydraulic pressure decreases and the
pistons are pulled clear of the rotor by the action of the
piston seals.
Rear Disc Brake Caliper
Rear disc brake calipers do the same job and have
roughly the same components as front brake calipers.
However, they are usually much smaller since the rear
brakes perform less of the braking work than the front
brakes. Virtually all rear brake calipers are single piston
floating designs.