Depending on the condition of the parts, the
mechanic may need to do one or more of the
operations. In any case. you must make sure the brake
assembly is in sound operating condition.
Disc Brake Pad Replacement
Disc brakes have flat linings bonded to a metal
plate or shoe. The pad is not rigidly mounted inside the
caliper assembly; thus, it is said to float. These pads are
held in position by retainers or internal depressions
(pockets machined into the caliper).
A visual inspection on the condition of the pads
can be made after the wheel and tire is removed. The
inner shoe and lining can be viewed through a hole in
the top of the caliper, whereas the outer shoe and
linings can be viewed from the end of the caliper.
A good rule in determining the need for pad
replacement is to compare lining thickness to the
thickness of the metal shoe. If the lining is not as thick
as the metal shoe, it should be replaced. The basic steps
for disc brake service are as follows:
1. Siphon two thirds of the brake fluid from the
master cylinder. This action prevents fluid
overflow when the caliper piston is pushed
7. Remove the caliper guide pins that holds the
caliper to the adapter. In typical applications,
positioners and bushings will come off with the
3. Lift the caliper off the adapter and away from
the rotor. Do NOT let the caliper hang by the
brake hose. Hook or tie the caliper to a
suspension member. This will allow the rotor to
be tested and inspected.
4. Remove old pads from the caliper and adapter.
Note the position of antirattle clips because they
may be reused if they are in good condition.
5. Using a C-clamp or large screwdriver. force the
piston back into the caliper. This action will
open the caliper wide enough for new, thicker
6. Install the antirattle clips on the new pads. Fit
the pads back into the caliper.
7. Slide the caliper assembly over the rotor.
Assemble the caliper mounting hardware in
reverse order of disassembly. Make sure all
bolts are torqued to the manufacturers
8. After new pads are installed, road test the
vehicle to make sure that the brakes are
operating properly and also seat the new pads.
Several (3 to 3) heavy braking applications will
It is acceptable to service just the rear or
front disc brakes. However. NEVER service
only the left or right brake assemblies; always
replace both sets to assure equal braking
Since disc brake systems vary, consult the vehicle
manufacturers service and repair manuals for specific
details on the type of disc brakes you are working on.
Servicing Caliper Assemblies
When a caliper is frozen, leaking, or has extremely
high mileage, it is to be serviced. Servicing disc brake
caliper assemblies involve the replacement of the
piston, seals, and dust-boots. To perform this type of
service. it is necessary to remove the caliper assembly
from the vehicle. Basic steps for servicing the caliper
assemblies are as follows:
Remove the piston from the caliper by using air
pressure to push the piston from the cylinder.
Keep your fingers out of the way when using
compressed air to remove the pistons from the
caliper. Serious hand injuries can result.
With the piston removed, pry out the old dust
boot and seal from the caliper. Keep all parts
organized on the workbench. Do not mix up
right and left side or front and rear parts.
Check the caliper cylinder wall for scoring.
pitting, and wear. Light surface imperfections
can usually be cleaned with a cylinder hone or
emery cloth. When honing, use brake fluid to
lubricate the hone. If excessive honing is
required, replace the caliper.
Check the piston for wear and damage. If any
problems are found, replace the piston. The
piston and cylinder are critical and must be in
Clean all parts with an approved cleaner. Wipe
the parts with a dry, clean rag. Then coat the
parts with brake fluid.
Assemble the caliper in reverse order of
disassembly. Using new seals and boots, fit the