Bendix AIR User Manual

Bendix® ADB 22X™, ADB 225™, SN6™, SN7™, SK7™ Air Disc Brakes

DESCRIPTION

Bendix® Air Disc Brakes 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.
Available in models with or without a combination spring
brake unit, these brakes may also include optional wear
sensors and/or wear diagnostic equipment.

OPERATION

Bendix Air Disc Brakes convert air pressure into braking
force. (See Figure 2.) 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, which pulls the outer brake pad
into the rotor. The clamping action of the brake pads on
the rotor applies braking force to the wheel.

FIGURE 1 - BENDIX® ADB 22X™ AIR DISC BRAKE

Service Brake

Chamber

Lever

Return Spring

Pressure

Plate

Pushrod

SD-23-7541

Supply Port

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 (sum of clearances on both sides of the rotor)
should be between 0.024 to 0.043 in. (0.6 and 1.1 mm).

Diaphragm

Eccentric Bearing

Bridge

Pad

Rotor

Inner Brake Pad

Outer Brake

FIGURE 2 - CROSS-SECTION VIEW SHOWING BRAKE
OPERATION

1

SAFE MAINTENANCE PRACTICES

WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
general precautions should be observed at all times:

1. Park the vehicle on a level surface, apply the parking
brakes, and always block the wheels. Always wear
safety glasses. Where specifically directed, the
parking brakes may have to be released, and/or
spring brakes caged, and this will require that the
vehicle be prevented from moving by other means
for the duration of these tests/procedures.

2. Stop the engine and remove ignition key when
working under or around the vehicle. When working
in the engine compartment, the engine should be
shut off and the ignition key should be removed.
Where circumstances require that the engine be in
operation, EXTREME CAUTION should be used to
prevent personal injury resulting from contact with
moving, rotating, leaking, heated or electrically
charged components.

3. Do not attempt to install, remove, disassemble
or assemble a component until you have read
and thoroughly understand the recommended
procedures. Use only the proper tools and observe
all precautions pertaining to use of those tools.

4. If the work is being performed on the vehicle’s
air brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS
dryer system or a dryer reservoir module, be sure
to drain the purge reservoir.

5. Following the vehicle manufacturer’s recommended
procedures, deactivate the electrical system in a
manner that safely removes all electrical power from
the vehicle.

6. Nev e r ex c e e d manufacturer’s re c o m m e nded
pressures.

7. Ne v er connect or disconnec t a hose or l i ne
containing pressure; it may whip. Never remove a
component or plug unless you are certain all system
pressure has been depleted.

8. Use only genuine Bendix
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.

9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.

10. Prior to returning the vehicle to service, make certain
all components and systems are restored to their
proper operating condition.

®

replacement parts,

®

air

11. For vehicles with Antilock Traction Control (ATC),
the ATC function must be disabled (ATC indicator
lamp should be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.

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.

BRAKE DUST WARNING:

AVOID CREATING DUST WHEN WORKING
WITH BRAKE PADS DUE TO POSSIBLE
CANCER AND LUNG DISEASE HAZARD.

While Bendix Spicer Foundation Brake LLC does
not offer asbestos-containing brake linings or disc
pads, the long-term effects of certain non-asbestos
fibers have not been determined. Current OSHA
Regulations cover exposure levels to some, but not all,
components of non-asbestos linings and pads. The
following precautions should be used when handling
these materials:

• Avoid creating dust. Compressed air or dry
brushing must never be used to clean brake
assemblies or the work area.

• Brake workers must take steps to minimize
their exposure to airborne brake lining particles.
Procedures to reduce exposure include: working
in a well-ventilated area, segregating areas where
brake work is performed, using local filtered
ventilation systems or enclosed cells with filtered
vacuums for all brake work. 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 or drinking,
should not use tobacco products in any form,
shower after working, and not wear work clothes
home. Work clothes should be vacuumed using
a high efficiency particulate filter (HEPA) vacuum
and laundered separately without shaking.

• OSHA Regulations regarding testing, disposal
of waste and methods of reducing exposure
for asbestos are set forth in 29 Code of Federal
Regulations §1910.001. These Regulations provide
valuable information which can be utilized to
reduce exposure to airborne particles.

• Material Safety Data Sheets on Bendix
brake pads, as required by OSHA, are available
from Bendix Spicer Foundation Brake LLC.

®

air disc

2

SERVICE DATA INDEX

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Safe Maintenance Practices. . . . . . . . . . . . . . . . . . . . 2

Air Disc Brake Sectional and Exploded Views

Air Disc Brake Identification . . . . . . . . . . . . . . . . . . . . 6

Rotor Identification

Electronic Wear Indicator Exploded Views. . . . . . . . . 6

Preventive Maintenance Schedule. . . . . . . . . . . . . . . 7

Running Clearance Inspection . . . . . . . . . . . . . . . . . . 7

Mechanical Wear Indicators . . . . . . . . . . . . . . . . . . .8-9

Electronic Wear Indicators, including

Hand Held Diagnostic Equipment . . . . . . . . . . . . . 10

Troubleshooting Flowchart

Brake Pads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Rotors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Caliper Running Clearance . . . . . . . . . . . . . . . . . . . 14

Adjuster Mechanism. . . . . . . . . . . . . . . . . . . . . . . . . 15

Guide Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16-17

. . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Preventive Maintenance

Troubleshooting

. . . . . . . . . . . . . . . . . . . . 11

Inspections

. . . . .4-5

Maintenance Procedures

Pad Replacement. . . . . . . . . . . . . . . . . . . . . . . . .18-19

Electronic Wear Indicator Replacement
Tappet and Boot Assemblies

Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Carrier/Caliper Assembly Replacement
Brake Actuator and Spring

Brake Replacement . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . .20-21

22-24

. . . . . . . . . . 25

26-27

3

1

Caliper

12

Pad

Assembly

58

Ring

9
Inner
Boot

5

Guide

Pin

22

Inner Seal

Caliper Bolt

Brass Bushing

40

7

Top Sectional View

161

Tappet

Bushing

16

Threaded Tube

13

Tappet and Boot

Assembly

45 Washer

26

Spring Clip

44

Pad Retainer Pin

Pad Retainer

10

Cover

Adjuster Cap

11

22

Inner

Seal

24

Turning

Device

Wear Sensor

Adjuster Unit

32
Chain
Wheel

37

30

Chain

33

23

61

Shear Adapter

27 Spring

17

Bridge

Caliper Bolt B

(Uses Solid Rubber Bushing)

161

58

Ring

Tappet

Bushing

Tappet

and Boot

Assembly

Inner
Boot

13

6c Guide Sleeve

9

Guide Pin

16

Threaded Tube

2

Carrier

39c

Caliper Bolt

Side Sectional

View

FIGURE 4 - SECTIONAL VIEW

68a Cap

39b

Caliper Bolt

2

Carrier

4a

Guide

Pin

6a

Rubber

Bushing

39a

Caliper Bolt

One of Three

Alternate
Caliper Bolt
Styles Used

4b

Guide Pin

6b

Rubber

Bushing

Main Diagram shows Caliper Bolt A

Caliper Bolt C

(Has External Metal

Cover)

68c

Cover

4c

12

Pad

Assembly

46

Rotor

Pad Assembly 12

(Uses Flexible Rubber Wear

Indicator Sleeve)

27

Spring

Bridge

19

Lever

17

18/1 Spring Brake or

18/2

Brake Chamber

43

Bolt

20

Eccentric

Bearing

4

One of Three Different
Caliper Bolt Styles are

Used (Designated by

A, B, or C)

39c

Caliper Bolt

68c

Cover

68a Cap

18/1 Spring Brake

Uses White Assembly

Grease

6b

Rubber

Bushing

6c Guide

Sleeve

39b

Caliper

Bolt

39a

Caliper Bolt

18/2

Brake

Chamber

6a

Rubber Bushing

Adjuster Cap

5

Guide

Pin

37

Guide

Shear

Adapter

10

Cover

4c

Pin

61

Bushing

Inner
Boot

7

Brass

58

Ring

9

Pre-Applied

Thread Adhesive

11

Pad Retainer

4a, 4b

Guide Pin

40

Caliper Bolt

44

Pad Retainer Pin

45

Washer

Inner
Boot

Spring Clip

Caliper

9

Ring

1

58

26

12/2

12/1

12

Pad Assembly

13

Tappet and Boot

Assembly

161

Tappet

Bushing

22

Inner Seal

Uses

White

Assembly

Grease

FIGURE 5 - EXPLODED VIEW ­FOR REFERENCE ONLY - MANY OF THE
PARTS SHOWN ARE ONLY FACTORY
SERVICEABLE AT THIS TIME.

Chain . . . . . . . . . . . . . . . . . . . . 30

KEY

Adjuster Cap. . . . . . . . . . . . . . . 37

Adjuster Unit. . . . . . . . . . . . . . . 23

Bolt . . . . . . . . . . . . . . . . . . . . . . 43

Brake Chamber . . . . . . . . . . 18/2

Brass Bushing . . . . . . . . . . . . . . 7

Bridge . . . . . . . . . . . . . . . . . . . . 17

Caliper . . . . . . . . . . . . . . . . . . . . 1

Caliper Bolt. . . . 39a, 39b, 39c, 40

Carrier. . . . . . . . . . . . . . . . . . . . . 2

Chain Wheel. . . . . . . . . . . . . . . 32

Cover . . . . . . . . . . . . . . . . . . . . 10

Eccentric Bearing . . . . . . . . . . . 20

Guide Pins . . . . . . . . 4a, 4b, 4c, 5

Guide Sleeve . . . . . . . . . . . . . . 6c

Inner Boot. . . . . . . . . . . . . . . . . . 9

Inner Seal . . . . . . . . . . . . . . . . . 22

Lever . . . . . . . . . . . . . . . . . . . . 19

Pad . . . . . . . . . . . . . . . . . . . . 12/1

Pad Holder Spring . . . . . . . . 12/2

Pad Assembly

Pad Retainer . . . . . . . . . . . . . . 11

2

Carrier

See Figure 9, on Page 6 for exploded
views of electronic wear indicators

Pad Retainer Pin . . . . . . . . . . . 44

Ring . . . . . . . . . . . . . . . . . . . . . 58

Rubber Bushings . . . . . 6a, 6b, 6c

Shear Adapter . . . . . . . . . . . . .

Spring . . . . . . . . . . . . . . . . . . . . 27

Spring Brake. . . . . . . . . . . . . 18/1

Spring Clip . . . . . . . . . . . . . . . . 26

Tappet and Boot Assembly
Tappet Bushing

Threaded Tube. . . . . . . . . . . . . 16

Turning Device . . . . . . . . . . . . . 24

. . . . . . . . . . . . . . 12

Washer . . . . . . . . . . . . . . . . . . . 45

Wear Sensor

61

. . . . 13

. . . . . . . . . . . . 161

. . . . . . . . . . . . . . . 33

Caliper Bolt A

Caliper Bolt. . . . . . . . 39a

Cap. . . . . . . . . . . . . . 68a

Guide Pin . . . . . . . . . .4a

Rubber Bushing . . . . .6a

Caliper Bolt B

Caliper Bolt. . . . . . . . 39b

Guide Pin . . . . . . . . . .4b

Rubber Bushing . . . . .6b

Caliper Bolt C

Caliper Bolt. . . . . . . . 39c

Guide Pin . . . . . . . . . . 4c

Cover . . . . . . . . . . . . 68c

5

AIR DISC BRAKE IDENTIFICATION

To determine which version of the Bendix air disc brake is
installed, locate the identification label near the guide pin
housing. See below for examples of the different styles of
label you may find.

FIGURE 6 - PART NUMBER LABEL LOCATION

Bendix Part No.

Serial No.

Brake Designation followed
by the Caliper/Carrier part
number

ROTOR IDENTIFICATION

Certain maintenance inspection procedures depend on
the type of rotor installed (See Page 13). See below for
examples of the different styles of rotor in use.

Spline Rotor

Conventional Rotor

Some air disc brakes carry the
Knorr-Bremse label shown below.

Type of
Caliper

Manufacturer's No.

Date of Manufacture

FIGURE 7 - PART NUMBER LABEL FIELDS

104

Type 1

Type 2

Cable Protection

Plate

Sensor

101

Sensor

104

Cable Protection

Plate

101

Sensor

101

Sensor

101

103

101

Sensor

101

Sensor

105

Cable Guide

11 Pad Retainer

Part No.

Axle or Vehicle

105 Cable

Guide

11 Pad

Retainer

FIGURE 8 - ROTOR IDENTIFICATION

104

Cable Protection

Plate

101

Sensor

Type 3

105a
Cable
Guide

Alternative to

103

Cable to Electrical

Supply

Item 105

Pad Retainer . . . . . . . . . . . . . . 11

Sensor . . . . . . . . . . . . . . . . . . 101

Cable to Electrical Supply . . . 103

Cable Protection Plate . . . . . . 104

Cable Guide . . . . . . . . . . . . . . 105

Cable Guide . . . . . . . . . . . . . 105a

101

Sensor

105

Cable Guide

11 Pad

Retainer

FIGURE 9 - ELECTRONIC WEAR INDICATOR COMPONENTS

6

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 e.g.
daily pre-trip inspections, etc.) Also, see the vehicle's
manual for recommendations.

Pad & Rotor Wear,

Vehicle Used for:

(Inspection with the wheel mounted)

Running Clearance

Use the table below for a guide to maintenance interval
planning, however, depending on the vehicle use, more

frequent checks of the components may be necessary.

Keep track of the results of your maintenance inspec­tions to assist you determine the ideal maintenance
interval for the vehicle.

Basic Inspection Program

At Least Once Annually and at

Every Pad Replacement

(Inspection with wheel removed)

Over the Road

e.g. Line haul, RV,
Open Highway Coach.

Higher Duty Use

e.g. Pick-Up & Delivery,
Off-Highway, Construction,
Loggers, Concrete Mixer,
Dump Truck,
City Transit Bus, Refuse,
Urban Region Coach,
School Bus.

• For vehicles with electronic wear indicators,

use the dash indicator(s) and/or the hand-held
diagnostic tool to regularly monitor the pad
wear.

• In all cases, visually inspect the wear indicator
(see Pages 8-9) every four months (or keep
track of the results of maintenance inspections
to schedule checks 4 to 5 times during the
pad lifetime). At the same time, conduct the
Running Clearance Inspection (see below).

• A visual check of the mechanical wear indicator
every time the tire pressures are checked is
recommended. Be alert for any rotor cracks,
etc. visible (See Page 13 for criteria.)

• For vehicles with electronic wear indicators,

use the dash indicator(s) and/or the hand-held
diagnostic tool to regularly monitor the pad
wear.

• In all cases, visually inspect the wear indicator

(see Pages 8-9) every three months (or keep
track of the results of maintenance inspections
to schedule checks 4 to 5 times during the
pad lifetime). At the same time, conduct the
Running Clearance Inspection (see below).

• A visual check of the mechanical wear indicator

every time the tire pressures are checked is
recommended. Be alert for any rotor cracks,
etc. visible (See Page 13 for criteria.)

Inspect:

• The rotor for cracks, etc. (see

Page 13 for criteria)

• The running clearance
and adjuster function (see
Page 15)

• The caliper travel (see Pages
16-17)

• The tappet and boot
assemblies (see Page 14)

• All covers, caps, hoses, and
brake exterior for damage etc.

Air Disc Brake Running Clearance Inspection.

Follow all industry safety guidelines, including those listed on Page 2. On
level ground, with the wheels chocked and the parking brake temporarily
released, check for movement of the brake caliper. This small movement,
less than 0.80" (2 mm) - approximately the thickness of a nickel - in the
inboard/outboard direction indicates that the brake is moving properly
on its guide pins. If the caliper has no movement or appears to move
greater than the distances above, a full wheel-removed inspection will be
necessary. See Page 16.

7

MECHANICAL BRAKE PAD AND ROTOR WEAR INDICATORS

A preliminary visual check of the condition of the brake pad/rotor
wear can be made without removing the wheels. See below
for the inspection to make for each of the three guide pin styles
in use for Bendix air disc brakes.

Style A and B

- Inspect position
of wear indicator

pin

Note: These inspections provide an indication of
when to schedule a full wheel-removed inspection of
the brake pads and rotor. The thicknesses of both the
pad and rotor will affect the wear indicator position at
which maintenance is actually needed.

These inspections do not constitute
“out-of-service” criteria.

Style A: Rolling Boot Style Wear Indicator

Inspect the position of the guide pin
flexible rubber bushing. See Figure

10. When the guide pin has moved
in so that the ribbed section of the
flexible rubber bushing reaches the
point where it folds back in, it is time
to schedule a full wheel-removed
inspection of the pads and rotor. Note:
This is only an indication that the pads
and rotor are ready for inspection,
and does not necessarily mean that
maintenance is required.

FIGURE 10 - ROLLING BOOT-STYLE WEAR INDICATOR INSPECTION

New

Style C and D -

Where the indicator

pin is covered (see
Figure 12), inspect

notches in carrier

and caliper or

backing plate - see

Page 9

Time to Schedule

Inspection of

Pads and Rotor

Style B: Solid Rubber Bushing Style Wear Indicator

Inspect the position of the guide pin
compared to the solid rubber bushing.
See Figure 11. When the guide pin
is aligned with the bushing, it is time
to schedule a full wheel-removed
inspection of the pads and rotor. Note:
This is only an indication that the pads
and rotor are ready for inspection,
and does not necessarily mean that
maintenance is required.

FIGURE 11 - SOLID RUBBER BUSHING-STYLE WEAR INDICATOR INSPECTION

New

Where the Guide Pin is enclosed

by a cover - see next page for

inspection criteria.

Time to Schedule

Inspect ion of

Pads and Rotor

FIGURE 12 - PIN COVER

8

MECHANICAL BRAKE PAD AND ROTOR WEAR INDICATORS (continued)

Style C: Where Both the Carrier and Caliper
Have an Indicator Notch

Compare the relative position of two notches cast into the
Carrier and Caliper. See Figure 13. When the two notches
align, it is time to schedule a full wheel-removed inspection
of the pads and rotor. Note: This is only an indication that
the pads and rotor are ready for inspection, and does not
necessarily mean that maintenance is required.

Location of

Inspection

Grooves

Notch in Caliper

Notch in

Carrier

Style D: Where Only the Caliper has an
Indicator Notch

When the notch in the Carrier aligns with the front edge of
the torque plate, it is time to schedule a full wheel-removed
inspection of the pads and rotor. Note: This is only an
indication that the pads and rotor are ready for inspection,
and does not necessarily mean that maintenance is
required.

Notches

Line Up

Time to Schedule

Inspection of

Pads and Rotor

FIGURE 13 - STYLE C - NOTCHED
CARRIER AND CALIPER

Notch in

Caliper

Backing

Plate

Lines Up

FIGURE 14 - CARRIER WEAR
INDICATOR NOTCH AND BACKING
PLATE ALIGNMENT

Torque

Plate

Time to Schedule

Inspection of

Pads and Rotor

9

11

Pad Retainer

101

Wear Sensor

Cable

Brake Pad Assembly

Example of

a Wear Sensor

(101) Installed into

Slot in Brake Pad

12

46 Rotor

To Vehicle Electronic

Monitoring System

or for use with

Diagnostic Tool

FIGURE 15 - EXAMPLE OF NORMALLY OPEN OR CLOSED
WEAR SENSOR

ELECTRONIC BRAKE PAD WEAR
INDICATORS

The electronic monitoring system uses sensors installed
in a pre-formed slot in the brake pad to allow the status of
the pad wear to be monitored. When the pad wears away
through use, the point is reached when the indicator itself
comes into contact with the rotor.

For in-pad Normally-Closed Indicators, when the point
is reached when the indicator itself is worn through, the
circuit flowing through it is broken and the vehicle operator
is alerted.

For in-pad Normally-Open Indicators, when the point
is reached when the indicator itself is worn through, the
circuit is completed by the rotor touching the contacts and
the vehicle operator is again alerted.

On some vehicles, the electronic system is fully integrated
into the vehicle monitoring system and uses a buzzer
or indicator lamp to alert the driver. Alternate vehicle
arrangements permit a hand-held diagnostic tool to be
used to test individual wheel connectors, or where installed,
attach to a DIN socket in the dash, and allow up to six
brakes to be checked from that location. The system
provides feedback on the pad wear and can also conduct
a test of the Wear Indicator Potentiometer.

Even when using wear indicators, always follow the
standard preventive maintenance schedule outlined on
page 7.

Refer to the vehicle manual and/or the diagnostic tool
manual for specific device operating instructions.

FIGURE 16 - EXAMPLE OF POTENTIOMETER WEAR
SENSOR

13-Pin Plug
(DIN 72570)

to vehicle

Plug for Individual

Wheel Inspection

FIGURE 17 - HAND HELD DIAGNOSTIC TOOL

10

GENERAL TROUBLESHOOTING PROCEDURE FLOWCHART

FIGURE 18 - TROUBLESHOOTING BENDIX AIR DISC BRAKES

11

INSPECTIONS

Follow all standard safety procedures including, but not
limited to, those on page 2 of this service manual.

BRAKE PADS AND ROTORS

Bendix Air Disc Brakes are precision-engineered braking
mechanisms. The “friction couple” braking characteristics
have been carefully optimized and the rotor design and
materials have been matched with special formulation
brake pads for optimal performance.

CAUTION: When replacing brake pads, Bendix
strongly recommends using only replacement pads
and replacement rotors approved by the OEM. Use
of non-approved rotors or non-approved replacement
disc pads can cause excess wear to brake components,
and can increase the risks of rotor cracking, etc. Note
that two thicknesses of backing plate are generally
available, so to maintain the vehicle within spec's
only use brake pads with the type of backing plate
and lining material originally supplied by the vehicle
manufacturer. See the manual supplied with the
vehicle for further information.

INSPECT BRAKE PADS

Regular inspection of the brake pads (even for vehicles
that use a wear indicator) is an important part of vehicle
maintenance.

See Figure 16. If the thickness of the friction material (M2)
is less than 0.079 in. (2 mm) the pads must be replaced.

Bendix® ADB 22X™, ADB 225™, SN6™, SN7™ (and some
SK7™) air disc brakes use 0.35 in. (9 mm) backing plates,
so P2 (the combined pad and backing plate thickness)
must be a minimum of 0.43 in. (11 mm).

®

Note that for some Bendix
(7 mm) backing plate is used, so P2 (the combined pad
and backing plate thickness) must be a minimum of 0.35 in.
(9 mm).

If the pad thickness is within the acceptable range, inspect
the pad surface. Minor damage at the edges is permitted
(see Figure 20), but replace the pads if major damage on
the surface of the pad is found (see Figure 21).

When replacing brake pads, Bendix strongly recommends
that all the brake pads on an axle be replaced at one time.
See pages 18-19 for the pad replacement procedure. Also
see the vehicle manual recommendations.

SK7™ air disc brakes, a 0.28 in.

B (Backing P2 (Pad min.

plate thickness) thickness)

Bendix® ADB 22X™,
ADB 225™, SN6™,
and some SK7™
Air Disc Brake Pads

SK7™ Air Disc Brake
Pads with 0.28 in.
(7 mm) backing plate

FIGURE 19 - PAD AND ROTOR DIMENSIONS

0.35 in. 0.43 in.
(9 mm.) (11 mm.)

0.28 in. 0.35 in.
(7 mm.) (9 mm.)

Small Amount of

Brake Material

Chipped from

Edge

FIGURE 20 - MINOR

PAD DAMAGE IS

ACCEPTABLE

FIGURE 21 - MAJOR

PAD DAMAGE IS

NOT ACCEPTABLE

Section

Damaged or

Missing

12

INSPECT ROTORS

Identify if the rotor is a conventional or a splined assembly
(see Page 6).

Examine the rotor and measure the thickness at thinnest
point. Avoid measuring near the edge of the rotor as minor
burrs may be present.

Replace Bendix rotors when the minimum thickness of

1.46 in. (37 mm) is reached or as instructed by vehicle
manufacturer. When replacing Rotors, please refer to the
instructions of the Vehicle Manufacturer. It is recommended
to install Bendix Brake Rotors, available from your local
Bendix Spicer Foundation Brake parts outlet, and it is
also recommended that the pads should be replaced at
the same time.

Non-Bendix rotors. If a non-Bendix rotor is used,
refer to the vehicle manual and rotor manufacturer’s
recommendations. CAUTION: The use of non-approved

brake rotors may reduce levels of safety and invalidate
warranty.

Rotor Surface Inspection

Inspect the rotor at each change of pads for grooves and
cracks. The action to take depends on the type of rotor,
and also the size, depth and direction of the imperfections,
see Figure 22.

Rotor Turning (Grinding)

Bendix rotors are normally service-free.

Turning of Bendix spline rotors is not permitted.

Conventional rotors may be turned when changing pads,
but is not normally necessary. In the case of severe
grooving of the entire friction surface, however, turning
could be useful, and may increase the load-bearing
surface of the pads. To meet Bendix recommendations,
the minimum rotor thickness after turning must be greater
than 1.53 in. (39 mm).

CAUTION: Always maintain air disc brake pads and rotors
within specifications. Excessive pad or rotor wear will
degrade optimum performance. When replacing Rotors, be
sure to adhere to the vehicle manufacturer’s recommended
bolt tightening torques.

A

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

Rotor
Friction
Surface

Width

“a”

D

Cracks reaching
either edge of the

rotor
are not
acceptable
for either
type of
rotor

a

Area D

Area A

C

C i r c u m f e r e n t i a l
Grooves, as in Area
C, are acceptable
if less than 0.06 in.
(1.5 mm) deep.

Area B

Area C

B

• For standard Bendix rotors, cracks

running in a radial direction, that is,
from the inside to the outside, (see
Area B), less than 0.06 in. (1.5 mm)
deep or wide are acceptable. Cracks
are only acceptable if they are less
than 75% of the width of the rotor
contact area (i.e. 75% of dimension
“a”).

• For spline Bendix rotors, radial

cracks are only acceptable if they
are less than 0.04 in. (1.0 mm) deep
or wide, and if they are less than
75% of the width of the rotor contact
area (i.e. 75% of dimension “a”).

In ad d it io n , f o l lo w t he
recommenda tions of the
vehicle manufacturer. An
axle should only have either
spline or standard rotors.

FIGURE 22 - EXAMPLES OF ACCEPTABLE AND NON-ACCEPTABLE ROTOR CRACKS AND GROOVES

13

2. CALIPER RUNNING CLEARANCE

CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.

CALIPER MOVEMENT TEST

Remove the wheel. With the spring brakes caged, push
the caliper assembly inboard on its guide pins. Using a
suitable tool, press the inboard pad (12) away from the
tappets and check the gap between the tappet and the
inboard pad backplate - it should be between 0.024 in.
(0.6 mm) & 0.043 in. (1.1 mm). If the movement is within

the range there is no need to inspect further.

CAUTION: If the clearance is too wide, there is a danger
of brake failure. If the clearance is too small, there is a
danger of overheating. That may lead to consequential
damage.

FIGURE 23 -
MEASURING
THE RUNNING
CLEARANCE

If there is no movement at all, go to pages 16-17 for
the “Guide Pin Inspection Procedure.”

If inst ead, there is movemen t, but the running
clearance is too small or too large, the adjuster may
not be functioning correctly and should be checked.
See “Inspect Adjuster Mechanism” on Page 15.

CONTACTING BENDIX

www.foundationbrakes.com

Bendix on-line information is available 24/7. In the on-line contacts directory, you can find:
technical support contacts; service engineers; Bendix account managers; international
contacts and more. www.foundationbrakes.com is your complete Bendix resource.

Bendix Technical Assistance Team

For direct personal technical support, call the Bendix technical assistance team at:

1-800-AIR-BRAKE (1-800-247-2725),

Monday through Friday, 8:00 A.M. to 6:00 P.M. EST, and follow the instructions in the
recorded message.

Alternatively, you may e-mail the Bendix technical assistance team at:
[e-mail].

To better serve you, please record the following information before you call the
Bendix Tech Team, or include this information in your e-mail:

• Bendix product model number, part number and configuration.

• Vehicle make and model.

• Vehicle configuration. (Number of axles, tire size, etc.)

• System performance symptoms: When do they occur?

• What troubleshooting/measurements have been performed?

• What Bendix service data literature do you have or need?

14

3. INSPECT ADJUSTER MECHANISM

CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.

Aside from the normal maintenance schedule, this
Adjuster Check is also carried out when the Caliper
Movement Test (see Page 14) finds that the running
clearance is too small or too large.

The adjuster should then be checked as follows:

With the spring brake released (or caged), remove the
adjuster cap (37) using the tab, taking care not to move
the shear adapter (61). Note: One of two styles of adjuster
cover (stamped metal or plastic) may be used.

Although exploded view (Figure 25) shows the adjuster (23)
and shear adapter (61) separated, only turn the adjuster
with the shear adapter installed on the adjuster. Using a
box-end wrench or socket, turn the Shear Adapter (61)
counter-clockwise and listen for the sound of 2 or 3 clicks
as the mechanism increases the running clearance. Note:
Do not use an open-ended wrench as this may damage
the adapter.

CAUTION: Never turn the adjuster (23) without the
shear adapter (61) installed. The shear adapter is a
safety feature and is designed to prevent an excess
of torque being applied to the adjuster. The shear
adapter will fail (by breaking loose) if too much torque
is applied.

If the shear adapter fails, you may attempt a second time
with a new (unused) shear adapter. A second failure of the
shear adapter confirms that the adjustment mechanism is
seized and the caliper must be replaced.

With a box-end wrench (or socket) positioned so that it
can turn freely without coming into contact with parts of
the vehicle (See Figure 27) on the shear adapter, make
five to ten moderate applications of the brakes [at about
30 psi (2 Bar)]. For a normally functioning Bendix air disc
brake, the box-end wrench or socket should turn clockwise
in small increments. NOTE: As the number of applications
increases, the turning movement will decrease (as the
brake reaches its normal calibration point).

If the box-end wrench or socket does not: (a) turn at all,
or (b) turns only with the first application, or (c) turns
forward and backward with every application, the automatic
adjuster has failed and the caliper/carrier assembly must
be replaced.

61

37

12

Inboard

Brake

12

Pad

Outboard

Brake Pad

FIGURE 24 - COVER REMOVAL

37

Cap

23 Adjuster

61 Adapter

37

Cap

Tab

FIGURE 25 - EXPLODED
VIEW OF ADJUSTER
AND ADAPTER

FIGURE 27 - ADJUSTMENT MECHANISM TEST

FIGURE 26 - TAB
POSITION

Tab

Bendix recommends installing a new adjuster cap (lightly
greased using white lithium-based grease) when returning
the air brake to service. Ensure that the tab is in the position
shown in Figure 26.

15

GUIDE PINS

CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.

Note: If the steps below lead the technician to a step where
the wheel needs to be removed, inspect first to see that
there is no contact between the caliper and axle, vehicle,
chassis sections or carrier, etc. that may be impeding the
caliper movement. When removing wheels, refer to the
vehicle manufacturer’s recommendations.

This guide pin inspection should be carried out if the
result of the Caliper Movement Test (see Page 13) is
that the technician cannot move the caliper.

GUIDE PIN BEARING INSPECTION

Use the following procedure to check caliper movement
along the guide pins:

Remove the Pads (see Page 18).

One of the three different styles of guide pin (A, B, or C)
may be present (See Figure 28). The bearings for styles
A and B use a rubber bushing, and style C uses a guide
sleeve. Clean dirt, road grime, etc. from the guide pin or
cover.

Using hand pressure only (no tools), the Caliper (1)
should slide freely along the whole length of the Guide
Pin arrangement. With the pads removed, this movement
should be at least 0.8 inch (20mm). If the movement is less
than this amount, replace the caliper/carrier assembly.

To measure the clearance from the rubber bushing (6a,
6b) or guide sleeve (6c) to the guide pin:

See Figures 29 and 30. Remove the wheel. Remove the
pad retainer (11), but leave the pads (12) in position. Attach
a magnetic dial-gauge holder to the carrier (2) on the short
bearing side of the caliper (1).

Use the measuring point on the caliper (1) - see the arrow
in Figure 28. Press the caliper in the direction of carrier
(2) and set the dial-gauge to zero.

Place a suitable tool (e.g. screwdriver) between Carrier
(2) and Caliper (1) forcing them in opposite directions, and
read the maximum value on the dial-gauge.

For styles A and B guide pins, if the value is greater than

0.079 in. (2.0 mm), or for style C guide pins, if the value
is greater than 0.039 in. (1.0 mm), the caliper/carrier
assembly must be replaced.

13

Tappet and Boot

1

Caliper

FIGURE 28 - GUIDE PINS

Assembly

Caliper

Movement

39c

Caliper Bolt

12 Pad Assembly

5

Guide Pin

6a

39a

4a

4b

6b

6c Guide Sleeve

4c Guide Pin

2

Caliper

Brass Bushing

39b

Cover

1

Carrier

7

10

Cover

BEARING SIDE

23

Adjuster Unit

61

Shear Adapter

37

Adjuster

Cap

SHORT

BEARING SIDE

68a

Cap

(6a): Rubber Bushing

(39a): Caliper Bolt

(4a): Guide Pin

(6b): Rubber Bushing

(39b): Caliper Bolt

(4b): Guide Pin

68c

LONG

16

FIGURE 29 - MAGNETIC DIAL-GAUGE

GUIDE PIN SEAL INSPECTION

Caliper Guide Pin Seals

The long bearing side guide pin (5) is sealed with the cover
(10) and with the inner boot (9). See Figure 28. Note: It
may be necessary to remove the pads to inspect the inner
boots (9) if pad wear is minimal. The guide pin (4a, 4b,
or 4c, depending on the style) is also sealed with an inner
boot (9) and a cover (style C), or a flexible rubber wear
indicator in the case of style A guide pins.

Inspect the above components, and if damage is found,
replace the caliper/carrier assembly. No kits are available
at this time for Guide Pin Seals.

TAPPET AND BOOT ASSEMBLY
INSPECTION

In order to inspect the tappet and boot assembly, it may
be necessary to remove the pads (12) (see Page 18) and
advance the shear adapter (61) clockwise (see Page 15)
until the boots are clearly visible.

13

Extend Less
Than 1.18 in.

(30 mm)

FIGURE 30 - TAPPET EXTENSION LIMIT

CAUTION: NEVER EXTEND THE TAPPET MORE THAN

1.18 in. (30 mm). Over-extending the tappet will result
in the tappet losing engagement with the threads of the
synchronizing mechanism. Since the mechanism can
only be set at the manufacturing plant, the CALIPER/
CARRIER ASSEMBLY MUST BE REPLACED if this
happens.

Inspect the tappet and boot assemblies (13) for evidence
of damage, corrosion, etc. The penetration of dirt and
moisture into the brake can lead to corrosion and impair
the function of the air disc brake. Replace as necessary
(see Pages 22-24).

After re-installing a wheel according to the vehicle
manufacturer’s recommendations, please ensure that there
is sufficient clearance between the tire inflation valve stem,
the caliper and the wheel rim, to avoid damage.

WARNING : Not all whee ls and valve stems are
compatible with Bendix Air Disc Brakes. Use only
wheels and valve stems approved by the vehicle
manufacturer to avoid risk of valve stem shear and
other compatibility issues.

17

MAINTENANCE PROCEDURES

PAD REPLACEMENT

CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.
When installing pads, where appropriate use heavy
duty gloves and always keep fingers away from
potential pinch hazard areas.

As noted earlier, Bendix Air Disc Brakes are precision­engineered braking mechanisms. The “friction couple”
braking characteristics have been carefully optimized and
the rotor design and materials have been matched with
special formulation brake pads for optimal performance.

PAD REMOVAL

Bendix strongly recommends that when replacing brake
pads, pads are replaced as an axle set.

Release or cage spring brakes and remove the wheel (refer
to the vehicle manufacturer’s recommendations).

Note: Before removing the brake pads it is strongly
recommended that the adjuster mechanism be checked
for correct operation (see Page 15).

Remove the clip (26) and washer (45), depress the pad
retainer (11) and remove the pad retainer pin (44). Discard
these four items - replacements are included in the service
kits. As necessary remove any in-pad wear sensor
components and discard.

Pull off the adjuster cap (37) using the tab, taking care to
keep the shear adapter (61) in position on the adjuster
(23).

Using a box-end wrench or socket, fully wind back the
tappet and boot assemblies (13) by rotating the shear
adapter (61) in an counter-clockwise direction (see Page

15). Note: Do not use an open-ended wrench as this may
damage the adapter.

CAUTION: Never turn the adjuster (23) without the
shear adapter (61) installed. The shear adapter is a
safety feature and is designed to prevent an excess
of torque being applied to the adjuster. The shear
adapter will fail (by breaking loose) if too much torque
is applied.

If the shear adapter fails, you may attempt a second time
with a new (unused) shear adapter. A second failure of
the shear adapter confirms that the adjustment mechanism
is seized and the caliper/carrier assembly must be
replaced.

To remove the outboard brake pad (12), slide the caliper

44

Pin

11 Pad Retainer

45 Washer

26 Clip

FIGURE 31 - BRAKE PAD REMOVAL

Inboard

Outboard

Brake Pad

12

FIGURE 32 - BRAKE PAD REMOVAL

(1) fully to the outboard position first. Similarly, to remove
the inboard pad, first move the caliper fully to the inboard
position, and then remove the pad. See Figure 32.

Inspect the rotor.

See Page 13 for full information.

Assembly

23

61

37

Inboard Pad

12

PAD INSTALLATION

CAUTION: When replacing brake pads take care
to always use the correct replacement pads. For
example, note that two thicknesses of backing plate
are generally available - to maintain vehicle within
spec's only use brake pads with the type of backing
plate and lining material originally supplied by the
vehicle manufacturer. See the manual supplied with
the vehicle for further information.

As noted above, Bendix strongly recommends that
when replacing brake pads, pads are replaced as an
axle set. Use only pads which are permitted by the

vehicle manufacturer, axle manufacturer and/or disc
brake manufacturer. Failure to comply with this may
invalidate the vehicle manufacturer’s warranty.

18

Check that the tappet and boot assemblies have been fully
retracted, as outlined above. Clean the brake as needed

- see the vehicle manufacturer’s recommendations.

To install the outboard brake pad (12), slide the caliper
(1) fully to the outboard position before inserting the pad
(with the brake lining material facing the rotor). Similarly,
to install the inboard pad, move the caliper fully to the
inboard position, and then install the brake pad (with the
lining material facing the rotor). See Figure 30.

Install new in-pad wear indicator kit, if appropriate (see
Pages 20-21).

Using a box-end wrench or socket, turn the shear adapter
(61) clockwise until the pads come into contact with the
rotor. Then turn back the shear adapter counter-clockwise
two clicks to set the initial running clearance.

Note: Use only pads with the same backing plate thickness
as originally specified for the vehicle’s brakes.

Note: The Bendix air disc brakes covered by this service
manual use more than one pad retainer design. Be sure
to install the correct part number for the vehicle.

After installing the pad retainer (11) supplied with the kit,
into the groove of the caliper (1), it must be depressed to
enable the insertion of the pad retainer pin (44).

Install the supplied washer (45) and spring clip (26) to
the pad retainer pin (44). It is recommended that the pad
retainer pin (44) be installed pointing downwards (see
Figure 35).

Apply and release the brake and then check that the hub
turns easily by hand.

Lightly grease and install a new adjuster cap (37) using
white lithium-based grease. Note: The tab of the adjuster
cap should be positioned as shown by the arrow in
Figure 34 for ease of access.

Re-install the wheel according to the vehicle manufacturer’s
recommendations. Note: Not all wheels (and or valve

stems) are compatible with Bendix Air Disc Brakes.
Use only wheels and valve stems approved by the
vehicle manufacturer.

CAUTION: Bendix recommends that after every air
brake service, if available, the technician checks the
brake performa nce and the syste m behavior on a
dynamometer.

Outboard

Backplate

of Pad

FIGURE 33 - PAD
INSTALLATION

37 Cap

Tab

44

Pin

Inboard

23

61

12

Inboard

Pad

12
Brake Pad
Assembly

FIGURE 34 - TAB POSITION

11 Pad Retainer

45 Washer

37

26 Clip

FIGURE 35 - BRAKE PAD INSTALLATION

19

ELECTRONIC WEAR INDICATOR
REPLACEMENT

(Normally-Closed or Normally-Open Type) See page 10.

New wear indicators are normally installed whenever brake
pads are replaced. Please see Brake Pad Installation on
Page 18 for cautions and procedures. The wear indicator
is installed after the new brake pads are installed into the
brake, but before the retainer hardware.

Remove and retain the pad holder springs.

See page 6 for typical contents of wear indicator kits.

Installation: The longer branch of the wear indicator cable
(see arrow) must be installed in the outboard pad. Insert
the Wear Indicator Cables (101) into the pre-cut slot in the
pads. The wear indicators snap into place.

1

101

Outboard Pad

Long

Cable

12/1

FIGURE 36 - WEAR INDICATOR CABLE

12/1

2

12/1

2. Insert wear indicator sensors into
the pads.

4

44

11

3

12/2

12/2

101

3. Install the pad holder springs (12/2)
onto the pads (12/1) with the wear
indicator cable (101) as shown.

5

105

20

45

26

101

4. Install the pad retainer (11), pad
retainer pin (44), washer (45) and
spring clip (26) with the wear indicator
cable (101) as shown.

5. Install the cable guide (105) onto
the pad retainer (11). The cable guide
(105) snaps into place when pressing
lightly onto the pad retainer (11).

6

101

short cable end

7

101

105a

6. Press the wear indicator cable
(101) into the locating tabs of the
cable guide (105) (see arrows A). The
short cable end of the wear indicator
cable (101) must not be secured by
locating tabs of the cable guide (105).
According to vehicle type, install
the cable that leads to the electrical
supply of the vehicle, in one of the two
locating tabs (see arrows B).

8

7. Install the indicator cable (101) in
the middle of the pad retainer (11).
Insert the cable guide (105a) at one
side of the pad retainer (11) (see
arrow B). Slightly press in on the
other side of the pad retainer (11) (see
arrows A). The cable guide (105a)
snaps into place.

According to vehicle type, install the
cable that leads to the electric supply
of the vehicle, in one of the wire loop
(see arrows C). The short end of the
wear indicator cable (101) must not
be secured by a wire loop of the cable
guide (105a) (see arrows C).

8. Carefully install the cable protection
plate (104) with attention to the correct
position of the cable protection plate’s
catch (see arrows).

The cable protection plate (104) will
snap into place.

21

TAPPET AND BOOT ASSEMBLIES
REPLACEMENT

CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.
When installing pads, where appropriate use heavy
duty gloves and always keep fingers away from
potential pinch hazard areas. Cage spring brakes
before beginning procedure.

Note: In some cases, the technician may find it easier to
remove the caliper from the vehicle before making the
replacement (see Page 25 for instructions on caliper/carrier
removal).

REMOVAL OF TAPPET AND BOOT
ASSEMBLIES (13)

Follow the procedure for removing brake pads (12) on
Page 18.

CAUTION: Never turn the adjuster (23) without the
shear adapter (61) installed. The shear adapter is a
safety feature and is designed to prevent an excess
of torque being applied to the adjuster. The shear
adapter will fail (by breaking loose) if too much torque
is applied.

CAUTION: NEVER EXTEND THE TAPPET MORE THAN

1.18 in. (30 mm). Over-extending the tappet will result
in the tappet losing engagement with the threads of the
synchronizing mechanism. Since the mechanism can
only be set at the manufacturing plant THE CALIPER/
CARRIER ASSEMBLY MUST BE REPLACED if this
happens.

Removal of the tappet and boot assembly (13) requires
the use of the wedge fork (A). See Figure 39. Extend the
tappets less than 1.18 in. (30 mm) by turning the shear
adapter (61) clockwise until there is sufficient access
to the boots to remove the tappet boot from the caliper
bore. A screwdriver (B) should be used to move the boot
location ring - see Figure 40 and allow the wedge fork (A)
to be inserted. CAUTION: Take care not to damage the
inner sealing face (see arrow “X” in Figure 40). Gouges
or grooves that would prevent a good seal necessitate
caliper replacement.

The tappet and boot assemblies (13) can then be removed
from the threaded tubes (16) by using the wedge fork
(A).

Remove the old tappet bushing(s) (161). Inspect the inner
sealing face (see arrow “X”) for damage. If damage is
found to the inner seal the caliper/carrier assembly must
be replaced.

Inboard

Outboard

23

61

Inboard Pad

12

12

FIGURE 37 - BRAKE PAD REMOVAL

B

13

13

Extend

Less Than

1.18 in.

(30 mm)

FIGURE 38 - TAPPET EXTENSION

Press-in Tool
arrangement for
Tappet and Boot

Assembly (13)

when Caliper

is fitted on the

vehicle.

Ring T24 for SK7

Brakes. Installation device for Tappet and

Boot Assembly (13) when Caliper is removed

™

and 225™ and 22X™ Air Disc

from axle.

Press-in Tool
arrangement for
Tappet and Boot

Assembly (13)

when Caliper is

removed from the

vehicle.

Press-in Tool (Z004190) for Tappet and

Boot Assembly (13) . . . . . . . . . . . . . . . T1, T2 T3, T4

Wedged Fork (II32202) for removal of

Tappet and Boot Assembly (13) . . . . . . . . . . T15

Ring (K004082) for Tappet and

Boot Assembly (13) . . . . . . . . . . . . . . . . . . . T24

FIGURE 39 - TAPPET REMOVAL TOOL

37

22

13

A

2.76 in.

(70 mm)

22

X

FIGURE 40 - WEDGE TOOL USE

A

13

161

16

46

12

16

FIGURE 42 - USE OF A SPACER (OFF VEHICLE USE)

13

161

FIGURE 43 - ON VEHICLE BOOT INSTALLATION

B

E

1

FIGURE 41 - USE OF A NEW BRAKE PAD AS A SPACER

INSPECT THE THREADED TUBES (16)

For the inspection of the threads, the tubes must be
extended, but by less than 1.18 in. (30mm), by turning the
shear adapter (61) clockwise. If working with the caliper
on the vehicle, the technician may place a new brake pad
(12) into the outboard gap to help avoid the loss of thread
engagement of the threaded tubes. If the work is being
carried out at a workbench, the technician may insert a 2.76
in. (70 mm) spacer (E) into the caliper (1) to help avoid the
loss of thread engagement. See CAUTION on Page 22.

Check the threads for rust, corrosion, or damage etc.
If there is evidence of damage to the threads, rust or
corrosion, the caliper/carrier assembly must be replaced
(see Page 25).

If the threads are in good condition, fully wind back the
threaded tubes (16) by turning the shear adapter (61)
counter-clockwise.

INSTALLING THE TAPPET AND BOOT
ASSEMBLIES (13)

Grease threads with white grease (Part No. II14525 or
II32868).

L

16

X

FIGURE 44 - INNER SEAL INSTALLATION

Screw back the threaded tubes (16), by turning the shear
adapter (61) counter-clockwise (see Cautions earlier in
these instructions).

The sealing seat in the caliper for tappet and boot
assemblies (13) must be clean and free of grease. See
Figure 44.

Fit a new tappet bushing (161) onto the center post of each
threaded tube (16).

L

22

23

B

13

FIGURE 45 - ON VEHICLE TAPPET INSTALLATION

Technicians working with the caliper installed on
vehicle:

• Install the boots using the press-in tool (B) with the short
press-in extension (T3) for positioning and pressing
into place - see Figure 43.

• Position a tappet assembly (13) onto each tappet
bushing. Using press-in tool (B) in a reversed
orientation with the press-in extension (T3) towards
the threaded tube, install each tappet onto its tappet
bushing - see Figure 45.

Technicians working with the caliper not installed on
vehicle:

• Install the boots using the press-in tool (B) with the
long press-in extension (T3 + T4) for positioning and
pressing into place - see Figure 43.

• Position a tappet (13) onto each tappet bushing. Using
press-in tool (B) in a reversed orientation with the press­in extension (T3 + T4) towards the threaded tube, install
each tappet onto its tappet bushing - see Figure 45.

After assembly, check that the tappet (13) is free to turn
in both directions.

Note: When installing the tappet for Bendix

®

ADB 22X™,
ADB 225™, and SK7™ disc brakes, use the supplemental
ring (T24), inserted into the tool (T2) - see Figure 48 - to
assist the installation, since the caliper’s back plate is too
thin using only Tool (B) to achieve the correct position.

B

13

FIGURE 46 - OFF VEHICLE BOOT INSTALLATION

13

B

FIGURE 47 - OFF VEHICLE TAPPET INSTALLATION

24

13

B

T24

FIGURE 48 - OFF VEHICLE - USE OF EXTRA TOOL FOR
SOME STYLES

CALIPER/CARRIER ASSEMBLY
REPLACEMENT

CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.

With the caliper/carrier assembly securely supported,
remove and discard the six bolts attaching the carrier to
the axle.

CAUTION: Do not attempt to use the pad retainer (11)
to attach any lifting device to the brake. The pad retainer
is not suitable for this purpose, and damage to the brake
and/or unsafe conditions may result.

Clean and inspect the axle contact area. See axle or
vehicle manual for instructions if damage is found.

CALIPER/CARRIER ASSEMBLY
INSTALLATION

The correct choice of caliper/carrier must be ensured by
using the air disc brake part number on the identification
label when ordering replacement parts. See Page 6.

Replacement caliper/carrier assemblies may be delivered
with a plastic cap, adhesive tape, or a breakthrough
diaphragm in the area of the actuator attachment. Remove
the cap or tape only after installing the replacement
caliper on the vehicle. If the replacement caliper has the
breakthrough diaphragm, it should be left in place.

FIGURE 49 - CALIPER/CARRIER ASSEMBLY
REPLACEMENT

If the replacement caliper/carrier assembly is equipped with
a potentiometer for wear indication, then the connection
must be made using the appropriate mating plug – refer
to the vehicle manufacturer’s recommendations.

CAUTION: See the cautions in this document with regard
to possible pinch hazard, and the restriction against using
the pad retainer (11) as a place to secure lifting devices.

With the replacement carrier/caliper assembly held in
position, install with new bolts. Note: Replacement bolts
are not supplied by Bendix - use only those of a grade and
type specified by the vehicle manufacturer. Consult the
vehicle manual for required torques.

25

BRAKE ACTUATOR AND SPRING BRAKE
REPLACEMENT

CAUTION: Replace actuator and spring brakes only
with the same as originally installed on the vehicle.
Replacement with alternate equipment (without written
authorization from Bendix and the vehicle manufacturer)
could compromise brake performance.

CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.

B

A

18/2

Brake

Chamber

B

or

18/1

Spring

Brake

Brake Chamber Removal

With all air pressure drained from the air brake system,
disconnect the air hose from the brake chamber (18/2).

Remove and discard brake chamber mounting nuts (see
Figure 50, arrows B).

Brake Chamber Installation

Note: New brake chambers (18/2) have drain plugs
installed (see Figure 50, arrows A). After installation,
remove whichever plug is at the lowest position. Be sure
that all other drain holes remain plugged. The drain hole
must be aligned downwards (or within ±30°) when installed
on the vehicle.

Before installing the new brake chamber, the actuator
flange (see Figure 51, arrow C) must be cleaned, and
inspected. Consult the vehicle manual. The spherical
cup in the lever (19) must be greased with white grease
(Part No. II14525 or II32868).

CAUTION: Do not use grease containing molybdenum
disulfate.

See Figure 52. The seal, as well as the pushrod area must
be clean and dry.

CAUTION: Do not use brake chambers with seals with a
thickness less than 0.12 in. (3 mm). Use only actuators
which are recommended by the vehicle manufacturer.

Install the brake chamber using new self-locking nuts (EN
ISO 10513). Tighten alternately both the nuts step by step
up to a final torque of 133 ± 7 ft. lbs (180 ± 10 Nm).

Re-connect the air hose and be sure that the hose is not
twisted or in contact with moving vehicle components. The
air hose routing must allow for full caliper travel. Test for
leakage and check the brake operation and effectiveness
before returning vehicle to service.

FIGURE 50 - ACTUATOR INSTALLATION

19

FIGURE 51 - ACTUATOR FLANGE

Seal

Pushrod area

FIGURE 52 - CAP INSTALLATION

C

0.12 in.

(3 mm)

26

Spring Brake Removal

CAUTION: Follow all standard safety procedures - see note
above. Be familiar with the spring brake manufacturer’s
recommended safety practices.

With all air pressure drained from the air brake system,
disconnect the air hose from the brake chamber (18/1).

Back out the release bolt (Figure 53, arrow D) using a
maximum torque of 26 ft. lbs. (35 Nm) to release spring
force on the pushrod. Refer to the spring brake and vehicle
manufacturer’s recommendations - in some cases it may
be permissible to cage the spring brake while the spring
brake is engaged. While supporting the spring brake in
position, remove and discard brake chamber mounting nuts
(see Figure 53, arrows B). Remove the spring brake.

A

B

A

D

18/1

B

Spring Brake Chamber Installation

Note: New spring brake chambers (18/1) have drain plugs
installed (see Figure 53, arrows A). After installation,
remove whichever plug is at the lowest position. Be sure
that all other drain holes remain plugged. The drain hole
must be aligned downwards (or within ±30°) when installed
on the vehicle.

Before installing the new brake chamber, the actuator
flange (see Figure 51, arrow C) must be cleaned, and
inspected. Consult the vehicle manual. The spherical
cup in the lever (19) must be greased with white grease
(Part No. II14525 or II32868).

CAUTION: Do not use grease containing molybdenum
disulfate.

See Figure 54. The seal, as well as the pushrod area must
be clean and dry.

CAUTION: Do not use brake chambers with seals with a
thickness less than 0.12 in. (3 mm). Use only actuators
which are recommended by the vehicle manufacturer.

Install the brake chamber using new self-locking nuts (EN
ISO 10513). Tighten alternately both the nuts step by step
up to a final torque of 133 ± 7 ft. lbs (180 ± 10 Nm).

Re-connect the air hose and be sure that the hose is not
twisted or in contact with moving vehicle components. The
air hose routing must allow for full caliper travel. Test for
leakage and check the brake operation and effectiveness
before returning vehicle to service.

FIGURE 53 - SPRING BRAKE INSTALLATION

0.12 in.
(3 mm)

Pushrod

area

Seal

FIGURE 54 - CAP INSTALLATION

27

28

BW7308 ©2005 Bendix Spicer Foundation Brake LLC • All rights reserved. • 12/05 • Printed in U.S.A.