User Guide

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Bendix

ADB 22X

™

, ADB 225

™

, SN6

™

, SN7

™

, SK7

™

Air Disc Brakes

SD-23-7541

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.

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).

FIGURE 1 - BENDIX

ADB 22X

™

AIR DISC BRAKE

FIGURE 2 - CROSS-SECTION VIEW SHOWING BRAKE

OPERATION

Supply Port

Return Spring

Pushrod

Lever

Outer Brake

Pad

Inner Brake Pad

Rotor

Eccentric Bearing

Service Brake

Chamber

Bridge

Pressure

Plate

Diaphragm

Summary of content (28 pages)

PAGE 1
SD-23-7541 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.
PAGE 2
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.
PAGE 3
SERVICE DATA INDEX Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Safe Maintenance Practices. . . . . . . . . . . . . . . . . . . . 2 Air Disc Brake Sectional and Exploded Views . . . . .4-5 Air Disc Brake Identiﬁcation . . . . . . . . . . . . . . . . . . . . 6 Rotor Identiﬁcation . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Electronic Wear Indicator Exploded Views. . . . . . . . . 6 Preventive Maintenance Preventive Maintenance Schedule . . . . . . . . . . . . . .
PAGE 4
12 Pad Assembly 58 Ring 1 Caliper 9 Inner Boot 22 5 7 Guide Inner Seal Brass Bushing Pin 40 Caliper Bolt Top Sectional View 10 Cover 23 Adjuster Unit 161 Tappet Bushing 32 Chain Wheel 16 Threaded Tube 13 Tappet and Boot Assembly 61 Shear Adapter 45 Washer 26 Spring Clip 37 Adjuster Cap 44 Pad Retainer Pin 27 Spring 30 Chain 11 Pad Retainer 17 Bridge 22 Inner Seal 33 Wear Sensor Caliper Bolt B (Uses Solid Rubber Bushing) 24 Turning Device 68a Cap 16 Threaded Tube 161 Tappet Bushing 13
PAGE 5
11 Pad Retainer 44 Pad Retainer Pin 26 Spring Clip 45 Washer 18/1 Spring Brake 58 Ring 18/2 Brake Chamber Uses White Assembly Grease 4c Guide Pin 9 Inner Boot 12/2 4a, 4b Guide Pin 12/1 One of Three Different Caliper Bolt Styles are Used (Designated by A, B, or C) 1 Caliper 13 Tappet and Boot Assembly 6b Rubber Bushing 39c Caliper Bolt 68c Cover 12 Pad Assembly 6c Guide Sleeve 61 Shear Adapter 7 Brass 6a Rubber Bushing Bushing 37 Adjuster Cap 39a 5 Caliper Bolt Guide Pin 39b Caliper Bolt 6
PAGE 6
AIR DISC BRAKE IDENTIFICATION ROTOR 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. 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 FIGURE 6 - PART NUMBER LABEL LOCATION Bendix Part No. Serial No.
PAGE 7
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. 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.
PAGE 8
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. Note: These inspections provide an indication of when to schedule a full wheel-removed inspection of the brake pads and rotor.
PAGE 9
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.
PAGE 10
11 Pad Retainer 101 Wear Sensor Cable Example of a Wear Sensor (101) Installed into Slot in Brake Pad To Vehicle Electronic Monitoring System or for use with Diagnostic Tool 12 Brake Pad Assembly 46 Rotor FIGURE 15 - EXAMPLE OF NORMALLY OPEN OR CLOSED WEAR SENSOR FIGURE 16 - EXAMPLE OF POTENTIOMETER 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.
PAGE 11
GENERAL TROUBLESHOOTING PROCEDURE FLOWCHART FIGURE 18 - TROUBLESHOOTING BENDIX AIR DISC BRAKES 11
PAGE 12
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.
PAGE 13
INSPECT ROTORS Rotor Surface Inspection Identify if the rotor is a conventional or a splined assembly (see Page 6). 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. 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.
PAGE 14
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. FIGURE 23 MEASURING THE RUNNING CLEARANCE CALIPER MOVEMENT TEST Remove the wheel.
PAGE 15
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.
PAGE 16
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.
PAGE 17
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.
PAGE 18
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.
PAGE 19
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.
PAGE 20
ELECTRONIC WEAR INDICATOR REPLACEMENT (Normally-Closed or Normally-Open Type) See page 10. 1 101 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. Outboard Pad Remove and retain the pad holder springs. 12/1 See page 6 for typical contents of wear indicator kits.
PAGE 21
7 6 101 101 105a short cable end 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). 7. Install the indicator cable (101) in the middle of the pad retainer (11).
PAGE 22
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.
PAGE 23
2.76 in. (70 mm) 13 A A 22 E 16 X 1 13 FIGURE 42 - USE OF A SPACER (OFF VEHICLE USE) 161 13 B FIGURE 40 - WEDGE TOOL USE 161 12 16 46 FIGURE 43 - ON VEHICLE BOOT INSTALLATION 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.
PAGE 24
13 B 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. FIGURE 46 - OFF VEHICLE BOOT INSTALLATION • Position a tappet assembly (13) onto each tappet bushing.
PAGE 25
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.
PAGE 26
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. B A 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.
PAGE 27
Spring Brake Removal A 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.