Figure 7-17.Floating caliper.
Additional pressure then forces the caliper
assembly to move in the opposite direction of the
piston, thereby forcing the brake pad on the
opposite side to contact the rotor.
As pressure is built up behind the piston, it forces
the brake pads to tighten against the rotor. This
action develops additional braking force.
SLIDING CALIPER TYPE.The
caliper type disc brake (fig. 7-18) is mounted in a slot
in the caliper adapter. It is a variation of the floating
caliper, using a single piston and operating on the same
principle, whereby the piston applies pressure to one
brake pad and the movable caliper applies pressure to
This design has two major sectionsthe sliding
caliper and the caliper adapter (anchor plate). Each has
two angular machined surfaces: this is where the
sliding contacts come into play. The machined
surfaces of the caliper housing slide on the mated
Figure 7-18.Sliding caliper.
surfaces of the caliper adapter when the brakes are
FIXED CALIPER.The fixed caliper disc brake
(fig. 7-19) is rigidly mounted to the spindle or splash
shield. In this design, the caliper usually is made in two
pieces and has two or more pistons in use.
The pistons accomplish the centering action of the
fixed caliper, as they move in their bores. If the lining
should wear unevenly on one side of the caliper, the
piston would take up the excess clearance simply by
moving further out of the bore.
As the brakes are applied, fluid pressure enters the
caliper on one side and is routed to the other through an
internal passage or by an external tube connected to the
opposite half of the caliper. As pressure is increased,
the pistons force the brake pads against the rotor
evenly, therefore maintaining an equal amount of
pressure on both sides of the rotor.
BRAKE SWITCHES AND CONTROL
There are several types of switches and control
valves used in hydraulic brake systems. Switches are
normally safety devices. and there are two types
usedthe stoplight switch and the braking warning
light switch. Control valves regulate pressure within
the braking system, and there are three typesthe
metering valve, the proportioning valve. and the