and adjust the spindle nut and install a new cotter pin.
Check that the rotor turns freely. Bearing service will be
covered in more detail in Chapter 17.
Final System Check and Road Test
Reinstall the tires and torque the lug nuts to specifica-
tions using a torque wrench or torque sticks, if available.
Simply tightening the lug nuts with an impact wrench can
lead to uneven torque, which could distort rotors and lead
to pulsation. Check the master cylinder reservoir and add
fluid if necessary. After adding fluid, pump the brakes a
few times to set the pad to rotor clearances. If necessary,
bleed the brake system.
Bedding-in Brake Pads
Road test the vehicle, making at least ten gentle
stops to seat the linings. This process is referred to as
bedding-in. Accelerate to about 35-40 mph (56-64 kph),
then apply the brakes with light to moderate pressure to
reduce speed to approximately 5 mph (8 kph); do not
come to a full stop. Allow at least 1/3 mile between stops.
Allow the brakes to cool completely before releasing the
vehicle to the customer.
While making these stops, be alert for noises, hard
pedal, and pulsation. If the rear brakes were serviced,
make sure that the parking brake works properly. It is a
good idea to check the parking brake even if the rear
brakes were not serviced. After you are sure that the vehi-
cle stops properly, return it to the owner. Caution the
owner to avoid hard prolonged braking for at least 200
miles (320 km).
Common disc brake problems are noise, pulsation,
and a hard pedal. The caliper hydraulic system is usually
trouble free. Disc brakes can be checked by observing the
thickness of the pads and the condition of the rotor.
The caliper can be removed by first removing the
wheel and tire to gain access. Then lightly pry the pads
away from the rotor and remove the caliper attaching
hardware. Then lift the caliper from the rotor and remove
the pads if necessary. Check the caliper for leaks and dam-
age. If necessary, check the pad thickness.
Push the piston into the bore with a C-clamp after
loosening the bleeder screw. Then install the new pads
with all hardware. Apply anti-squeal and high temperature
lubricant if necessary, then reinstall the caliper over the
rotor. Install and tighten the mounting hardware.
Common rotor problems include thickness variations,
warping, and heat damage. To remove the rotor, determine
what kind it is. Some rotors can be taken off the hub after
the caliper is removed, while others are removed by
removing the wheel bearing cotter pin and nut. The rotor
and hub can then be pulled from the spindle.
Rotors can be turned on or off of the vehicle.
Correctly mount the rotor in the arbor using the proper
adapters. Then adjust the cutters to take off needed mate-
rial. Make rough cuts to remove a great deal of metal, and
finish cuts to produce a smooth final surface. Hot spots can
be removed by grinding. Swirl grind to place a non-direc-
tional finish on the turned rotor.
After turning, install the rotor, add fluid to the reservoir
if necessary, and road test the vehicle. Check brake operation
and seat the brake pads, then return the vehicle to the owner.
Review Questions—Chapter 13
Please do not write in this text. Write your answers on
a separate sheet of paper.
1. Why should you use wire to hang the caliper to the
body, or place it where it will not hang?
2. Before pushing the piston into the caliper body on
some ABS vehicles, you should loosen the ______.
3. Anti-squeal compound, when used, should be
installed between the disc brake pads and the ______
mounting surfaces.
Chapter 13 Disc Brake Service 227
Figure 13-35. One type of hand-held swirl grinder used to
produce a “non-directional” rotor finish. This unit is powered by
the lathe arbor, which turns a flexible drive shaft (not shown).
The grinder spins at approximately twice the speed of the lathe
arbor shaft. (Ammco)
Warning: Do not attempt to move the vehicle
until the brake pedal has been pumped
several times. If brake clearances are exces-
sive (common after the pads have been replaced),
the brake pedal will go to the floor without applying
the brakes.
discs 120 grit
Lathe arbor
Flexible drive
cable housing
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