Lesson 1/Learning Event 1
DISK BRAKES
FIGURE 8. DISK BRAKE ASSEMBLY.
The disk brake, like the drum brake assembly, is operated by
pressurized hydraulic fluid. The fluid, which is routed to the
calipers through steel lines and flexible highpressure hoses,
develops its pressure in the master cylinder. Once the brake pedal
is depressed, fluid enters the caliper and begins to force the piston
(s) outward. This outward movement forces the brake pads against the
moving rotor. Once this point is reached, the braking action begins.
The greater the fluid pressure exerted on the piston(s) from the
master cylinder, the tighter the brake pads will be forced against
the rotor. This increase in pressure also will cause an increase in
braking effect. As the pedal is released, pressure diminishes and
the force on the brake pads is reduced. This allows the rotor to
turn more easily. Some calipers allow the brake pads to rub lightly
against the rotor at all times in the released position. Another
design uses the rolling action of the piston seal to maintain a
clearance of approximately 0.005 inches when the brakes are released.
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