Floating
Pin

35 Double-Diaphragm-Style
Spring Brake Chamber

‘A’ or ‘B’
cast here

Type ‘A’

Type ‘B’

44
Pad Retainer Pin

18/1 Spring Brake
Actuator

11 Pad Retainer
18/2
Service
Actuator

26 Spring Clip
12/2 Pad Holder Spring
Wheel
Rotation
On most vehicles, Type A
calipers are used on the
passenger side of the vehicle.
(There are some rare driver
side applications.)

(NOTE: Pad Assembly
consists of 12/1 plus 12/2)

45
Washer

Wheel
Rotation
On most vehicles, Type B
calipers are used on the driver
side of the vehicle. (There are
some rare passenger side
applications.)

Shield
Kit
(Drive or
Steer)

12/1 Pad
7
Brass
Bushing

22
Inner Seal
161
Tappet Bushing
13 Tappet
and Boot
Assembly

10
40
Caliper Cap
5
Bolt
Guide
Pin
68
Cap
39 Caliper Bolt
4 Guide Pin

Actuator
Hardware

37*

*37 Adjuster
Caps (2 styles
supplied in kits)

6 Guide Sleeve

61
Shear
Adapter

Carrier
Mounting
Hardware

1
Caliper
(or Caliper Kit)

U-shaped Rotor
58
Ring

9
Inner Boot
Bendix® ADB22X®
Anchor Plate
2A
Bendix
ADB22X
Carrier

(Rotor Shield for Trailers)
U-shaped
Rotor
Fasteners

2B
Bendix®
ADB22X®-V
Carrier

SD-1
Drive Hub
SD-2
SD-3

Steer Hub

Splined Disc Rotor
(SD)

Splined Disc®
Rotor Hardware
SD-1, -2, -3

Bendix
ADB22X-V
Anchor Plate

Carrier
Mounting
Hardware

See Section 4.2 for exploded view
of electronic wear indicator.

Figure 8 – Exploded View - Bendix ® ADB22X®, ADB22X® -V, and ADB22X® -LT Air Disc Brakes
INDEX TO FIGURES 7 AND 8
Adjuster Caps . . . . . . . . . 37
Adjuster Unit . . . . . . . . . . 23
Bolt . . . . . . . . . . . . . . . . . 43
Brass Bushing . . . . . . . . . . 7
Bridge . . . . . . . . . . . . . . . 17
Caliper . . . . . . . . . . . . . . . . 1
Caliper Bolt . . . . . . . . 39, 40
Cap . . . . . . . . . . . . . . . . . 68
Carrier . . . . . . . . . . 2 (A or B)
Chain . . . . . . . . . . . . . . . . 30

Chain Wheel . . . . . . . . . . 32
Cap . . . . . . . . . . . . . . . . . 10
Eccentric Bearing . . . . . . 20
Guide Pins . . . . . . . . . . . 4, 5
Guide Sleeve . . . . . . . . . . . 6
Inner Boot . . . . . . . . . . . . . 9
Inner Seal . . . . . . . . . . . . 22
Lever . . . . . . . . . . . . . . . . 19
Pad . . . . . . . . . . . . . . . . 12/1
Pad Holder Spring . . . . . 12/2

Pad Assembly . . . . . . . . . 12
Pad Retainer . . . . . . . . . . . 11
Pad Retainer Pin . . . . . . . 44
Ring . . . . . . . . . . . . . . . . . 58
Service Actuator . . . . . . 18/2
Shear Adapter . . . . . . . . . 61
Spring . . . . . . . . . . . . . . . 27
Spring Brake Actuator . . 18/1
Spring Brake Chamber (DoubleDiaphragm-Style) . . . . . . . 35

Spring Clip . . . . . . . . . . . . 26
Tappet and Boot
Assembly . . . . . . . . . . . . 13
Tappet Bushing . . . . . . . 161
Threaded Tube . . . . . . . . 16
Turning Device . . . . . . . . 24
Washer . . . . . . . . . . . . . . 45
Continuous Wear Sensor
(Optional) . . . . . . . . . . . . . 33

7

SECTION TWO: PREVENTIVE MAINTENANCE SCHEDULE AND WHEEL-ON INSPECTIONS
2.0 PREVENTIVE MAINTENANCE
Regular inspection and maintenance of air disc brake
components is an important part of vehicle maintenance.
The maintenance practices outlined here are recommended
in addition to all standard industry practices (including
daily pre-trip inspections.) Also, see the vehicle's manual
for recommendations. Keep track of the results of your
maintenance inspections to assist you in determining the
ideal maintenance intervals for the vehicle.

* For vehicles with
electronic wear
indicators, use the dash
indicator(s) and/or the
hand‑held diagnostic tool
to regularly monitor the pad
wear. See Section 4.2.
** Ensure hoses are properly
routed without kinks or
abrasion.

Use the table below for a guide to maintenance interval
planning, however, depending on the particular vehicle's
use, more frequent checks of the components may be
necessary.

Section Two
Section

2.0
2.1
2.2

Table 1: Inspection Period
(4 to 5 times during the pad lifetime)

When
you
check
the tire
pressure

About every four (4)
months for over-theroad applications:

About every three (3) months
for higher-duty applications:

e.g. line haul, RV,
open-highway
coaches, etc.

e.g. pick-up and delivery, offhighway, construction, logger,
concrete mixer, dump truck,
city transit bus, refuse, school
buses, etc.

Inspections with the wheel mounted (Sections 2.1 - 2.2)
Inspect the pad thickness by
checking the mechanical wear
indicators*. See Section 2.1.
Inspect the running clearances using
the quick inspection technique.
See Section 2.2.
Inspect the visible part of the rotors
for cracks, etc. See Section 2.1.3.

Inspections with wheel removed (Section 3)
Inspect the pads and entire rotor
surfaces for cracks, etc. (Bendix®
Splined Disc® rotors: Inspect
retaining hardware and check
torques) See Section 2.1.3 and 3.4.
Inspect the running clearances and
adjuster operation.
See Sections 2.2 and 3.2.
Inspect the caliper running
clearance. See Section 3.1.
Inspect the tappet and boot
assemblies. See Section 3.6.
Inspect all caps, hoses, and brake
exterior for damage etc.**

Table 1 – Preventive Maintenance Schedule
8

Page

Preventive Maintenance . . . . . . 8
Brake Pad and Rotor Inspections . . 9-10
Running Clearance Quick Inspection . . 10

At the
very
least,
every
four (4)
months

At least
once
every
year
(and at
every
pad
replacement)

2.1 BRAKE PAD AND ROTOR INSPECTIONS
Visual checks of the condition of the brake pad/rotor wear
can be made without removing the wheels. Where dust
guards are not used, the top of the pads and part of the
rotor are visible through the opening at the top of the brake.
Other visible portions of the rotor can be inspected at the
same time.
Unless a vehicle has been stored for some time, the main
rotor surfaces that contact the pads will always have a shiny
appearance. Surface rust on these surfaces indicates a
malfunctioning brake that should be inspected immediately.

Wear Indicator Style A:
Where both the carrier and caliper have an
indicator notch.
Compare the relative position of two notches cast into
the carrier and caliper. When the two notches align, it
is time to schedule a full, wheel-removed inspection
of the pads and rotor.

Notch in the
caliper

Pads are 1.181 in. (30 mm) thick when new (backing plate
and friction material) and must be replaced when the friction
material reaches 0.125 in. (3.2 mm) regardless of the
backing plate thickness. Bendix rotors are 1.77 in.
(45 mm) thick when new and must be replaced when
they reach 1.46 in. (37 mm). See Section 3.3 for further
inspection criteria.

2.1.1 Electronic Wear Indicators
Use the dash indicator(s) and/or a hand-held diagnostic
tool to regularly monitor the pad wear. See Section 4.2.

Notch in
the carrier

When the notches
line up, it is time
to schedule an
inspection of the
pads and rotor

2.1.2 Mechanical Wear Indicators
See Figure 9 for the location of the mechanical wear
indicators. There are two types (See Figure 10 for Style
A and Figure 11 for Style B).
Quick Visual
Inspection of Pad
Thickness and
Rotor

Location of Wear
Indicator Notches
(Both sides of
brake)

Figure 10 – Style A - Both Carrier and Caliper have a
Cast Notch

Wear Indicator Style B:
Where only the caliper has an indicator
notch.
When the notch in the caliper aligns with the front
edge of the torque plate, it is time to schedule a full
wheel-removed inspection of the pads and rotor.

Figure 9 – Location of Wear Indicators
NOTE: These mechanical wear indicators do
not constitute “out‑of‑service” criteria. These
inspections only show when to schedule a full wheelremoved inspection of the brake pads and rotor.
The thicknesses of the pad and rotor will both affect
the wear indicator position at which maintenance is
actually needed.

Notch in
the caliper

No notch
in the
carrier
When the
torque plate
edge lines up
with the notch,
it is time to
schedule an
inspection of
the pads and
rotor

Torque
plate

Figure 11 – Carrier Wear Indicator Notch and
Backing Plate Alignment
9

H

F
No action is needed
for small cracks
spread over the
surface (e.g. Area F).

Rotor
Friction
Surface
Width “f”

Area
F

• For standard Bendix® rotors, cracks
running in a radial direction — like
spokes of a wheel (see Area H) — less
than 0.06 in. (1.5 mm) deep or wide are
acceptable if they do not reach either
edge (see Area G). Cracks are only
acceptable if the length of the crack is
less than 75% of dimension “f” (the width
of the rotor contact area).

Area
H

f

Area G
G
Cracks reaching
either edge of the
rotor
are not
acceptable
for either
type of
rotor.

Area J

J
Circumferential
grooves, as in Area
J, are acceptable
if less than 0.06 in.
(1.5 mm) deep.

• For Bendix® Splined Disc® rotors,
radial cracks are only acceptable if they
are less than 0.04 in. (1.0 mm) deep
or wide and if they do not reach either
edge (see Area G). Crack lengths must
be less than 75% of dimension “f” (the
width of the rotor contact area).

In addition, follow the recommendations
of the vehicle manufacturer.
NOTE: Axles should have either
all Bendix splined discs (or all
conventional) rotors. A mirror or
boroscope camera can be used to
assist with inspections. Inspect for
spongiosis and rotor cheek separation
in the cooling vanes. When addressing
splined disc rotors, look for tooth
shearing and damage.

Figure 12 – Examples of Acceptable and Non-acceptable Rotor Cracks and Grooves

2.1.3 Rotor Quick Inspection
See Figure 12. See the various potential rotor conditions
that you may find. See the criteria below for whether the
rotor needs to be replaced and/or scheduled for a full
inspection.

clearance range is 0.024 - 0.047 in. (0.6 - 1.2 mm).
If the caliper movement or running clearance are unable
to be confirmed, complete a wheels-off inspection. See
Section 3.1.

2.2 RUNNING CLEARANCE QUICK
INSPECTION
CAUTION: Follow all safe maintenance practices.
On level ground, when the brake is at ambient temperature,
with the wheels chocked, and the parking brake
temporarily released, verify there is sufficient running
clearance between the pads. Using hand pressure
only (no tools) check for inboard/outboard movement
of the brake caliper. The small movement is less than
0.08 in. (2 mm) – approximately the thickness of
a nickel – indicates that there is sufficient running
clearance and the caliper is sliding freely. For a more
accurate reading, a dial indicator may be used to
measure running clearance. Recommended running
10

Push/Pull
By Hand
to Check
the
Running
Clearance

Figure 13 – Caliper Running Clearance (Wheel Not
Shown)

SECTION THREE: WHEEL-OFF MAINTENANCE INSPECTIONS
Section Four
Section

3.0
3.1
3.2
3.3-3.4
3.3
3.4
3.4.3
3.5
3.6

Page

Wheel-Off Inspections . . . . . . 13
Running Clearance Test . . . . . . 13
Adjuster Mechanism Inspection . . . 14
Brake Pads and Rotors . . . . . 15-17
Inspect the Brake Pads . . . . . . 16
Inspect the Rotor . . . . . . . . 17
Machining (Grinding or Turning) Rotors
18
Guide Pin Bearing Inspection . . . 18-19