Disc Brakes; Drum Brakes - Chevrolet Trailblazer Service Manual

substitute a new lamp, make continuity checks, and, finally, replace the switch as
necessary.
The hydraulic system may be checked for leaks by applying pressure to the pedal
gradually and steadily. If the pedal sinks very slowly to the floor, the system has a leak.
This is not to be confused with a springy or spongy feel due to the compression of air
within the lines. If the system leaks, there will be a gradual change in the position of the
pedal with a constant pressure.
Check for leaks along all lines and at wheel cylinders. If no external leaks are apparent,
the problem is inside the master cylinder.

Disc Brakes

Disc brake systems utilize a disc (rotor) with brake pads positioned on either side of it. An
easily-seen analogy is the hand brake arrangement on a bicycle. The pads squeeze onto
the rim of the bike wheel, slowing its motion. Automobile disc brakes use the identical
principle but apply the braking effort to a separate disc instead of the wheel.
The disc (rotor) is a casting, usually equipped with cooling fins between the two braking
surfaces. This enables air to circulate between the braking surfaces to aid in cooling the
rotor.. Dirt and water do not drastically affect braking action since contaminants are thrown
off by the centrifugal action of the rotor or scraped off the by the pads. Also, the equal
clamping action of the two brake pads tends to ensure uniform, straight line stops. Disc
brakes are inherently self-adjusting. There are three general types of disc brake:
A fixed caliper.
A floating caliper.
A sliding caliper.
The fixed caliper design uses two pistons mounted on either side of the rotor (in each side
of the caliper). The caliper is mounted rigidly and does not move.
The sliding and floating designs are quite similar. In fact, these two types are often lumped
together. In both designs, the pad on the inside of the rotor is moved into contact with the
rotor by hydraulic force. The caliper, which is not held in a fixed position, moves slightly,
bringing the outside pad into contact with the rotor. There are various methods of attaching
floating calipers. Some pivot at the bottom or top, and some slide on mounting bolts. In
any event, the end result is the same.

Drum Brakes

Drum brakes employ two brake shoes mounted on a stationary backing plate. These
shoes are positioned inside a circular drum which rotates with the wheel assembly. The
shoes are held in place by springs. This allows them to slide toward the drums (when they
are applied) while keeping the linings and drums in alignment. The shoes are actuated by
a wheel cylinder which is mounted at the top of the backing plate. When the brakes are
applied, hydraulic pressure forces the wheel cylinder's actuating links outward. Since these
links bear directly against the top of the brake shoes, the tops of the shoes are then forced