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

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

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

Caliper

Pad

Assembly

Ring

9 Inner Boot

Guide

Inner Seal

Caliper Bolt

Brass Bushing

Top Sectional View

161

Tappet

Bushing

Threaded Tube

Tappet and Boot

Assembly

45 Washer

Spring Clip

Pad Retainer Pin

Pad Retainer

Cover

Adjuster Cap

Inner

Seal

Turning

Device

Wear Sensor

Adjuster Unit

32 Chain Wheel

Chain

Shear Adapter

27 Spring

Bridge

Caliper Bolt B

(Uses Solid Rubber Bushing)

161

Ring

Tappet

Bushing

Tappet

and Boot

Assembly

Inner Boot

6c Guide Sleeve

Guide Pin

Threaded Tube

Carrier

39c

Caliper Bolt

Side Sectional

View

FIGURE 4 - SECTIONAL VIEW

68a Cap

39b

Caliper Bolt

Carrier

Guide

Rubber

Bushing

39a

Caliper Bolt

One of Three

Alternate Caliper Bolt Styles Used

Guide Pin

Rubber

Bushing

Main Diagram shows Caliper Bolt A

Caliper Bolt C

(Has External Metal

Cover)

68c

Cover

Pad

Assembly

Rotor

Pad Assembly 12

(Uses Flexible Rubber Wear

Indicator Sleeve)

Spring

Bridge

Lever

18/1 Spring Brake or

18/2

Brake Chamber

Bolt

Eccentric

Bearing

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

Rubber

Bushing

6c Guide

Sleeve

39b

Caliper

Bolt

39a

Caliper Bolt

18/2

Brake

Chamber

Rubber Bushing

Adjuster Cap

Guide

Shear

Adapter

Cover

Bushing

Inner Boot

Brass

Ring

Pre-Applied

Thread Adhesive

Pad Retainer

4a, 4b

Guide Pin

Caliper Bolt

Pad Retainer Pin

Washer

Inner Boot

Spring Clip

Caliper

Ring

12/2

12/1

Pad Assembly

Tappet and Boot

Assembly

161

Tappet

Bushing

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

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

. . . . 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

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

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.

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

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

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

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