NHTSA ID Number: 10200752
Manufacturer Communication Number: SD-23-7541
TSB/Document Date: 2021-09-01
Summary
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.
SD-23-7541
®
Bendix® ADB22X®, ADB22X®-V & 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 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 air disc brake is designed for
trailer applications.
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 No.
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 techteam@bendix.com.
2
Bendix® Air Disc Brake
Max.
permissible
Bendix®
cylinder
size
ADB22X®-LT
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.
ADB22X®
WARNING: If pads or rotors show
Service
brake
system
T24
T18
Parking
brake
system
T24/24
HFL1
T18/24
DDSB
SERVICE DATA INDEX
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: Troubleshooting Procedure Flowchart . . . . . . . . . . . . . . . . . 11
Section Four: Wheel-Off Maintenance Inspections . . . . . . . . . . . . . . . . . . . . . 13
4.0 Wheel-Off Inspections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1 Running Clearance Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.2 Adjuster Mechanism Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.3 Inspect The Brake Pads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.4 Inspect The Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.5 Guide Pin Bearing Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.6 Tappet And Boot Assembly Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Section Five: Maintenance Kits And Procedures . . . . . . . . . . . . . . . . . . . . . . .
5.0 Maintenance Kits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.0.1 General Information About Bendix Air Disc Brake Maintenance . . . . . . . . .
5.1 Air Disc Brake Dust Shield Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.2 Pad Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.3 Caliper/Carrier/Actuator Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.4 Spring or Service Brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.5 Tappet & Boot Assemblies and Tappet Inner Seal Replacement . . . . . . . . .
5.6 Guide Pin and Boot Assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.7 Bendix® Splined Disc® Hub Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
21
23
23
24
27
30
32
37
43
Section Six: U-Shape Rotor Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
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.
1.4 Operation
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.
Bendix® Splined
Disc® Rotor
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.
Electronic
Wear Sensor
(if installed)
104
Cable Protection Plate
Version 1
101
Sensor
101
Sensor
106
Mounting Pin
103
Cable to Electrical
Supply
Consult the instruction sheet included with wear
indicator kits for installation information.
Figure 5 – Electronic Wear Indicator Components
4
Version 2
104
Cable
Protection Plate
103
Cable to Electrical
Supply
Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Cable to Electrical Supply . . . . . . . . . . . . 103
Cable Protection Plate . . . . . . . . . . . . . . . 104
Cable Guide - Not Shown (two designs) . 105
Mounting Pin . . . . . . . . . . . . . . . . . . . . . . 106
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
1.4.1 Brake Release and Adjustment
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 0.043 in. (0.6 to 1.2 mm).
5
1
Caliper
12
Pad
Assembly
9
58 Inner Boot
Ring
5
22
Inner Seal
Guide Pin
7
Brass Bushing
Top Sectional View
40
Caliper Bolt
10
Cap
161
Tappet
Bushing
23
Adjuster Unit
32
Chain Wheel
61
Shear Adapter
16
Threaded Tube
13
Tappet and Boot
Assembly
45 Washer
26
Spring Clip
37
Adjuster Cap
27 Spring
44
Pad Retainer Pin
30
Chain
11
Pad Retainer
17
Bridge
22
Inner
Seal
16
Threaded Tube
161
Tappet
Bushing
13
Tappet
and Boot
Assembly
33
Wear Sensor
24
Turning
Device
2
Carrier
39
Caliper Bolt
Side Sectional View
12
Pad
Assembly
18/1 Spring Brake
or
18/2
Brake Chamber
46
Rotor
43
Bolt
27
Spring
6
68
Cap
58
Ring
12
Pad Assembly
Figure 7 – Sectional Views
6
Guide Sleeve
2
Carrier
19
17 Lever
Bridge
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 fixedpin side of the caliper first.
Fixed-Pin
(longer pin)
Floating
Pin
‘A’ or ‘B”
cast here
Type ‘A’
44
Pad Retainer
Pin
Type ‘B’
35 Double-Diaphragm-Style
Spring Brake Chamber
11 Pad Retainer
18/1 Spring Brake
Actuator
18/2
Service
Actuator
26 Spring Clip
12/2 Pad Holder Spring
(Note: Pad Assembly
consists of 12/1 plus 12/2)
45
Washer
Wheel
Rotation
Wheel
Rotation
On most vehicles, Type A calipers
are used on the passenger side of the
vehicle. (There are some rare driver
side applications.)
On most vehicles, Type B calipers are
used on the driver side of the vehicle.
(There are some rare passenger side
applications.)
12/1 Pad
7
Brass
Bushing
22
Inner Seal
Shield
Kit
(Drive or
Steer)
161
Tappet Bushing
13 Tappet
and Boot
Assembly
U-shaped Rotor
Actuator
Hardware
10
40 Cap
5 Caliper
Guide Bolt
Pin
61 37*
Shear
Adapter
68
Cap
39 Caliper Bolt
4 Guide Pin
6 Guide Sleeve
*37 Adjuster
- Mixes well with conventional fluids
- Low-moisture formula provides excellent vapor lock...
- Ideal for hydraulic and disc brakes
- Provides an extra margin of safety in extreme braking...
- Mix of polyglycol ethers ensures hot brake-system operation...
- Excellent for ABS, disc and drum brake systems
- Delivers braking power when needed by avoiding a spongy...
- Both wet and dry boiling points exceed the minimum...
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TSB/Document ID: SD-23-7541
Replacement Service Bulletin Number:
MFR Communication Date: 2021-08-30
MFR Internal Campaign ID/Software Version:
Communication Type: Service Bulletin/Repair Instructions
NHTSA Components: SERVICE BRAKES, AIR
MFR Component System:
MFR Component Subsystem:
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