204 Auto Brakes
Figure 12-23. An assortment of noise reducing items. A—Shims and springs. B—Four anti-rattle springs. C—Anti-squeal springs
in their mounting position. (Chevrolet)
Anti-rattle
springs
Anti-rattle
springs
Anti-rattle
springs
Caliper carrier
Anti-squeal
shim (outboard)
Anti-squeal
shim (inboard)
Anti-squeal shim
(inner outboard)
Anti-squeal
shim (inner
inboard)
Brake
pads
A
B C
Anti-squeal
springs
Anti-squeal
springs
Figure 12-24. One type of anti-squeak compound. This type is
meant to be applied to the back of the pad.
compounds, Figure 12-24. Most are designed to be
installed on the back of a brake pad before installation, in
the same location as an insulator. A few graphite-based
compounds are designed to be placed on the friction mate-
rial itself. Read the directions on the compound before use.
Lining Wear Warning Devices
A small piece of flat spring steel called a wear
indicator is frequently attached to one of the shoes. As
the pad linings wear down to their minimum thickness,
the end of the spring contacts the spinning rotor. A high
pitched squeal is produced whenever the brakes are not
applied, alerting the driver that it is time for brake ser-
vice. Operation of a typical wear indicator is depicted
in Figure 12-25.
Another type of wear indicator consists of an electri-
cal lead attached next to or inside the pad, Figure 12-26.
When the ignition switch is in the on position, an electri-
cal circuit exists through a dashboard light to this sensor.
If the pads wear down far enough, the electrical lead
contacts the rotor when the brakes are applied. This
grounds the lead and completes the circuit, illuminating
the dashboard light.