SD-23-7541
Bendix® ADB22X®, ADB22X®-V, and ADB22X®- LT Air Disc Brakes
SECTION ONE: AIR DISC BRAKE OVERVIEW
1.0 DESCRIPTION
Bendix® ADB22X®, ADB22X®-V, and ADB22X®-LT Air Disc
Brakes (ADB) use a floating caliper design to provide
foundation braking on all axles of heavy commercial
vehicles, buses, and trailers. Bendix air disc brakes provide
safety and performance as well as ease of service.
The ADB22X and ADB22X-LT for tractor disc brakes mount
to the axle's anchor plate (torque plate) using fasteners
that are installed parallel to the axle, while the anchor-plate
fasteners used for the Bendix ADB22X-V air disc brakes
install at right angles to the axle. The ADB22X-LT ADB is
designed for tractor, truck, and trailer in lighter-duty cycle
applications (e.g., city delivery and line haul) with chamber
sizes up to T18.
Available with or without a combination spring brake unit,
these brakes may also include optional wear sensors and
wear diagnostic equipment.

Section One
Section

1.0
1.1
1.2
1.3
1.4
1.4.1

Page

Description . . . . . . . . . .
Air Disc Brake Identification . . . . .
Rotor Identification . . . . . . . .
Wear Sensor Identification . . . . .
Operation . . . . . . . . . . .
Brake Release and Adjustment . . . .

1
1
4
4
4
5

1.1 Air Disc Brake Identification
Locate the identification label near the guide pin housing.
See below for information about the label fields used.

Label

Figure 2 – Typical Part Number Label Location

Bendix Part Number
Serial Number
Customer Part Number

Figure 3 – Part Number Label Information

Figure 1 – Bendix ® ADB22X® Air Disc Brakes

1

WARNING: Not all wheels and valve stems are
compatible with Bendix® Air Disc Brakes. Use only
wheels and valve stems approved by the vehicle
manufacturer to avoid the risk of valve stem shear
and other compatibility issues.
WARNING: AVOID CREATING
DUST. POSSIBLE CANCER AND LUNG
DISEASE HAZARD.
While Bendix Commercial Vehicle Systems LLC
does not offer asbestos brake linings, the long-term
affects of some non-asbestos fibers have not been
determined. Current Occupational Safety and Health
Administration (OSHA) Regulations cover exposure
levels to some components of non-asbestos linings,
but not all. The following precautions must be used
when handling these materials.
Avoid creating dust. Compressed air or dry brushing
must never be used for cleaning brake assemblies
or the work area.
▲ Bendix recommends that workers doing brake
work must take steps to minimize exposure
to airborne brake lining particles. Proper
procedures to reduce exposure include working
in a well-ventilated area, segregation of areas
where brake work is done, use of local filtered
ventilation systems or use of enclosed cells with
filtered vacuums. Respirators approved by the
Mine Safety and Health Administration (MSHA)
or National Institute for Occupational Safety
and Health (NIOSH) should be worn at all times
during brake servicing.
▲ Workers must wash before eating, drinking, or
smoking; shower after working, and should not
wear work clothes home. Work clothes should
be vacuumed and laundered separately without
shaking.
▲ OSHA & EPA Regulations regarding testing,
disposal of waste, and methods of reducing
exposure for asbestos are set forth in 29 &
40 Code of Federal Regulations §1910.1001 &
61.150, respectively. These Regulations provide
valuable information which can be utilized to
reduce exposure to airborne particles.
▲ Safety Data Sheets on this product, as required
by OSHA, are available from Bendix. Call
1-800-247-2725 and speak to the Tech Team or
email [email protected].

WARNING: Do not install LT brakes on high duty
cycle applications such as city bus, refuse, school bus,
or applications with piston-style park brake chambers.

2

WARNING: If pads or rotors show

ADB22X®LT

ADB22X®Reman

Max.
permissible
Bendix®
actuator
size

ADB22X®

signs of premature wear or failure, verify the
brake chamber is sized appropriately for the
application. An over-sized brake chamber can
result in excessive force being applied to the
brake pads and rotors. Additionally, under-sized
brake chambers can result in too little braking
force being applied to the brake and could
increase the time and distance needed to stop
the vehicle. See the table on the right for brake
chamber guidelines.

Bendix® Air Disc Brake

Service brake
system

T24

T18

T20

Parking brake
system

T24/24
HFL1

T18/24
DDSB

T20/24

TABLE OF CONTENTS
Section One: Air Disc Brake Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Safe Maintenance Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.0 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.1 Air Disc Brake Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 Rotor Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Wear Sensor Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4.1 Brake Release and Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1
2
1
1
4
4
4
5

Section Two: Preventive Maintenance Schedule and Wheel-On Inspections . 8
2.0 Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Brake Pad and Rotor Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Running Clearance Quick Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Section Three: Wheel-Off Maintenance Inspections . . . . . . . . . . . . . . . . . . . . 13
3.0 Wheel-Off Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Running Clearance Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 Adjuster Mechanism Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3 Inspect The Brake Pads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4 Inspect The Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.5 Guide Pin Bearing Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.6 Tappet And Boot Assembly Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Section Four: Maintenance Kits And Procedures . . . . . . . . . . . . . . . . . . . . . .
4.0 Maintenance Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.0.1 General Information About Bendix Air Disc Brake Maintenance . . . . . . . . .
4.1 Air Disc Brake Dust Shield Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Pad Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3 Caliper/Carrier/Actuator Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.4 Spring or Service Brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.5 Tappet and Boot Assemblies and Tappet Inner Seal Replacement . . . . . . .
4.6 Guide Pin and Boot Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.7 Bendix® Splined Disc® Hub Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

20
21
23
23
24
27
30
32
37
43

Section Five: U-Shape Rotor Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Section Six: Troubleshooting Procedure Flowchart . . . . . . . . . . . . . . . . . . . . 11
Contacting Bendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3

1.2 Rotor Identification

1.3 Wear Sensor Identification

See Figure 4 to help you identify which type of rotor is used
on the axle being inspected. Note that the maintenance
inspection procedure will depend on the type of rotor
installed.

See Figure 5 for the electronic wear sensor that may be
present.

1.3.1 Wear Sensor Function and Maintenance
Bendix pad wear sensors clip onto each brake pad and are
intended to wear away as the brake wears away. Bendix
pad wear sensors are a wearable item.

Bendix® Splined
Disc® Rotor

Bendix continuous wear sensing brakes are assembled with
a calibrated continuous wear sensor housed inside of the
adjuster cover. The continuous wear sensor and adjuster
cover are not wearable items and are mated to the caliper
for the entirety of its life. Removal of the adjuster cover
violates any warranty.

Conventional
Rotor

Figure 4 – Rotor Identification
CAUTION: Rotors may not be mixed on a single axle:
axles are only permitted to have all conventional or all
Bendix® Splined Disc® brake rotors.

Continuous Electronic Wear Sensor
(if installed)
Harness
Connector
Harness
Connection

In-pad Version 1

In-pad Version 2

104
Cable
Protection
Plate

101
Sensor

101
Sensor

Built-in
Sensor

106
Mounting Pin

iSense Pro
Adjuster
Cover

104
Cable
Protection
Plate

103
Cable to
Electrical Supply

103
Cable to
Electrical Supply

Consult the instruction sheet included with
wear indicator kits for installation information.

Figure 5 – Electronic Wear Indicator Components

4

Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Cable to Electrical Supply . . . . . . . . . . . . 103
Cable Protection Plate . . . . . . . . . . . . . . . 104
Cable Guide - Not Shown (two designs) . 105
Mounting Pin . . . . . . . . . . . . . . . . . . . . . . 106

1.4 Operation

1.4.1 Brake Release and Adjustment

Bendix® air disc brakes convert air pressure into braking
force. See Figure 6. When the vehicle brakes are applied,
air enters the service brake chamber through the supply
port, applying pressure within the diaphragm. The pressure
expands the diaphragm – applying force to, and moving,
the pressure plate and pushrod forward. The pushrod
acts against a cup in the internal lever – which pivots on
an eccentric bearing – moving the bridge. Moving against
a return spring, the bridge transfers the motion to two
threaded tubes and tappets, which move the inner brake
pad. The inner brake pad (from its normal position of having
a running clearance between it and the rotor) moves into
contact with the brake rotor. Further movement of the
bridge forces the caliper – sliding on two stationary guide
pins – away from the rotor. That, in turn, pulls the outer
brake pad into the rotor. The clamping action of the brake
pads on the rotor applies braking force to the wheel.

When the vehicle brakes are released, the air pressure
in the service brake chamber is exhausted and the return
springs in the chamber and the bridge return the air disc
brake to a neutral, non-braked position. To maintain the
running clearance gap between the rotor and the brake
pads over time, the non-braked position is mechanically
adjusted by a mechanism in the caliper. The adjustment
mechanism operates automatically whenever the brakes
are activated, to compensate for rotor and brake pad
wear and to keep the running clearance constant. During
pad or rotor maintenance, the technician manually sets
the system’s initial non-braked position. The total running
clearance (the sum of clearances on both sides of the rotor)
should be between 0.024 to 0.047 in. (0.6 to 1.2 mm).

Service Brake
Chamber

Inner Brake Pad
Outer Brake
Pad

Lever

Pressure Plate

Supply Port

Pushrod

Return Spring

Diaphragm
Rotor

Bridge
Eccentric Bearing

Figure 6 – Sectional View Showing Brake Operation

5

1
Caliper

12
Pad
Assembly

9
Inner Boot
22
58
Inner Seal
7
5
Ring
Brass Bushing
Guide
Pin
40
Caliper Bolt
10
Cap

161
Tappet
Bushing

Top Sectional View

23
Adjuster Unit

32
Chain Wheel

16
Threaded Tube
13
Tappet and Boot
Assembly

61
Shear Adapter

45 Washer
26
Spring Clip

37
Adjuster Cap
27 Spring

44
Pad Retainer Pin
30
Chain

11
Pad Retainer

17
Bridge

Pad Wear
Sensors
(Optional)

16
Threaded Tube

22
Inner
Seal

33
Continuous
Wear Sensor
(Optional)
24
Turning
Device

161
Tappet
Bushing
13
Tappet and
Boot Assembly

6
Guide Sleeve

2
Carrier

2
Carrier

39
Caliper Bolt

Side Sectional View
12
Pad
Assembly

58
Ring
12
Pad Assembly
18/1 Spring Brake or
18/2 Brake Chamber

46
Rotor

43
Bolt
27
Spring

Figure 7 – Sectional Views
6

68
Cap

17
Bridge

19
Lever

20
Eccentric
Bearing

9
Inner
Boot

4
Guide Pin

Short Caliper Bolt
Sectional View

For Bendix ® Air Disc Brakes,
as a vehicle travels forward,
the wheel always rotates
towards the fixed-pin side of
the caliper first.

Fixed-Pin
(longer pin)