While carefully prying against the piston, use the vice
grips to apply and release the parking brake. The caliper
piston should adjust the pads until they just rest against the
rotor. If the caliper piston fails to move, try tapping the
caliper piston area with a ball peen hammer. Be careful not
to damage the bleed screw. If the piston continues to stick,
remove the caliper and perform an overhaul.
The following sections discuss the service of disc
brake rotors. The condition of the rotor is as important as
pad condition. Many common disc brake problems, such
as noises and pulsation, are caused by the rotor. Therefore,
it is very important that you carefully check the rotors
when the pads are replaced.
Sometimes the rotor is not refinished when the pads
are replaced. However, the usual procedure in most shops
is to refinish the rotor to allow it to wear into the new disc
pads. Whether it is refinished or not, the rotor should be
checked as explained in the following paragraphs.
218 Auto Brakes
Note: In some cases, this is easier to
perform using a box-end wrench.
Figure 13-20. This particular brake caliper setup requires the
tab on the brake shoe to be placed in one of four caliper piston
cutouts (slots). (Nissan)
piston p s o
Figure 13-19. A—Parking brake lever removal can allow a screw caliper’s piston to be pressed in. B—Pressing the caliper piston in
with two pairs of adjustable pliers. (General Motors)
brake ca abl e
Caution: Some manufacturers recommend
that rotors be refinished only if they are
scored or out-of-round, which would pro-
duce a pulsation. In some cases, extensive driving is
required after refinishing to burnish the pads prop-
erly. Some rotors cannot be machined and must be
replaced if they are scored or out-of-round.