J05019 Rockwell Wheel Speed Front Disc Brakes J5-5
NOTE: These bolts are highly stressed and should
be replaced whenever their condition appears
questionable. A 3/4-16 UNF-28 tap lubricated with a
light oil may be used to inspect tapped holes in
housings for thread damage and to clean up any
minor thread roughness.
10. Brake housings and pistons should be thor-
oughly cleaned. After cleaning, passages, cavi-
ties, and external surfaces should be blown dry
with clean, dry, compressed air. Piston should
also be cleaned and blown dry.
NOTE: Cleaned and dried parts should not be left
exposed for any appreciable time without a
protective coating of lubricant; for short term storage,
coating all internal cavities, passages, and bosses
with hydraulic fluid will be adequate protection; for
longer term storage wipe cavities, connector bosses,
and threads with a protective grease, such as
petroleum jelly.
BRAKE LINING
Replacement
Each front wheel speed disc assembly has three
(some trucks may have four) calipers on one disc.
Each caliper has six pistons and two linings, three
apply pistons and one lining for each side of disc.
Lining should be changed when friction material is
worn to 0.125 in. (3.22 mm) thickness.
Failure to replace lining when worn to limits will
result in loss of braking and possible cata-
strophic failure.
1. To replace front linings, remove front tire and
rims, refer to “Wheel and Tire Installation”, Sec-
tion “G”.
2. Remove end plates (7 or 8) Figure 5-3 from
either end of caliper.
3. Pry between lining and disc to force pistons to
bottom in caliper housing.
4. Remove lining from inboard and outboard sides
of disc.
5. Inspect dust seals. Seals should be soft, pli-
able, and show no evidence of hardening or
rupture. If damage is observed, the dust covers
must be replaced. This will require disassembly
of the caliper.
6. Inspect end plates for wear. Replace if grooves
will not allow lining back plate to slide freely.
7. Inspect disc for wear limits, Figure 5-4. If disc is
worn below the limits shown, the disc must be
replaced. Refer to “Wheel and Tire Installation”,
Section “G”.
8. If original linings have sufficient lining material
for reuse, inspect lining back plate for cracks or
excessive yielding where plate fits into end
plates 7 or 8 (Figure 5-3).
When replacing linings, never mix new and used
linings in a brake assembly.
9. Slide linings (9) into caliper. It may be neces-
sary to again pry pistons into housing (1).
10. Install end plates (7 & 8), apply Loctite
®
271 to
threads of end plate capscrews (6). Install cap-
screws and tighten to 403 ft.lbs. (54.6 N.m)
torque. Check that linings (9) slide freely
between end plates.
11. After completing lining replacement, reinstall
front wheels. Refer to “Wheel and Tire Installa-
tion”, Section “G”.
FIGURE 5-4. DISC WEAR LIMITS
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