Average difference inboard to outboard should be
no greater than 0.138 in. (3.5 mm).

4.3.3

See Figure 24.

4.3.3

D

Surface
damage

E

Tears & cuts

Inspect for minor chips near the
edge and cracks on the face
(permitted) vs. major sections
damaged or missing.

Inspect the tappet and guide pin
Any damage must be repaired.
boots for cuts, cracks, and tears.

Melting

Inspect as Item E above,
but also check the running
clearance before removing the
brake pads.

G

Binding

With the pads removed, the
caliper should move freely by
hand. Re-torque the carrier to
anchor plate bolts per the OE
spec and procedure, if binding.

See Figure 26 (slide) and Table 4 (torque).

H

Excessive
play

Feel for excessive play between
the caliper and the carrier.

See Figure 27.

F

Worn

Rotors

I

Measure the rotor thickness
with a long jaw caliper.

Any damage must be repaired.

4.5.4 &
4.6.2
2.2 &
4.6.1

4.5.1 &
5.3

4.5.2

Thickness must be greater than 1.46 in.
(37 mm).
4.4

J

Surface
damage

Minor cracks and grooves are
acceptable, but check for cracks
See Figure 25 for surface details.
over the inside and outside
edges.

Replace the pads on both
sides of the worn axle.

Replace the pads on both
sides of the worn axle and
replace the guide pins as
needed.

Replace the pads on both
sides of the worn axle.

Replace the damaged
boots and replace the
resultant internal corroded
guide pins as needed.
Replace the worn guide pins
as needed and replace the
anchor plate if the re-torque
procedure does not resolve
the issue.
Replace the worn guide
pins as needed.
Refer to the OEM
recommendations for nonBendix® rotors. For Bendix
rotors, replace the rotors on
both sides of the axle.
Refer to the OEM
recommendations for nonBendix rotors. For Bendix
rotors only, replace the
rotor that is damaged.

Non-Serviceable: These are non-serviceable items and pending warranty terms; these issues may be covered under
warranty.
Adjuster
not rotating

L

Adjuster
too tight,
dragging
brake

With the brakes released, check
the running clearance between
the tappet and the inboard pad.

Calipers

K

If the second shear adapter
breaks while turning the
10 mm box-end wrench
counterclockwise, the adjuster
is seized.

12

Adjuster must turn in both directions with a hand
wrench.

The gap should be between
0.024 in. (0.6 mm) and 0.043 in. (1.1 mm).

4.2

Caliper only must
be replaced with
malfunctioning adjuster.

4.1

Install and torque the
replacement caliper
per section 5.3.7.

SECTION FOUR: WHEEL-OFF MAINTENANCE INSPECTIONS
Section Four
Section

4.0
4.1
4.2
4.3-4.4
4.3
4.4
4.4.3
4.5
4.6

Page

Wheel-Off Inspections . . . . . . 13
Running Clearance Test . . . . . . 13
Adjuster Mechanism Inspection . . . 14
Brake Pads and Rotors . . . . . 15-17
Inspect the Brake Pads . . . . . . 16
Inspect the Rotor . . . . . . . . 17
Machining (Grinding or Turning) Rotors
18
Guide Pin Bearing Inspection . . . 18-19
Tappet & Boot Assembly Inspection . . 19

two long-blade feeler gauges to measure – over the whole
tappet surface – the gap between them and the inboard pad
backplate. (See Figure 16.) The gap should be between
0.024 in. (0.6 mm) and 0.043 in. (1.1 mm). If the gap is
within the range given, the test is complete.

4.0 WHEEL-OFF INSPECTIONS
CAUTION: During these inspections, follow all safe
maintenance practices, including those on page 2 of this
service manual. Also, follow 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.

Pull
Caliper
Inboard

Figure 15 – Pull Caliper Inboard

4.0.1 Wheel Removal and Re-Installation
Refer to the vehicle manufacturer’s recommendations for
removing the wheel.
Note: When removing the wheel, 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
free movement of the caliper.

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

4.1 RUNNING CLEARANCE TEST
CAUTION: Follow all safe maintenance practices.

Check the clearance at
both tappets simultaneously:
0.024 in. to 0.043 in.
(0.6 mm to 1.1 mm)
Figure 16 – Running Clearance Check
CAUTION: If the clearance is too wide, there is a
danger of brake failure. If the clearance is too small,
or if there is no gap at all, there is a danger of the brake
overheating. These conditions must be corrected
before returning the vehicle to service.
For further investigation, where there is some gap, go to
Section 4.2 and check the adjuster mechanism. Where
there is no movement at all (and no gap to measure), go
to Section 4.5 “Guide Pin Inspection.”

Remove the wheel. With the spring brakes released or
caged, push the caliper assembly inboard on its guide
pins. Note: To fully release the spring brakes, ensure that
the air system pressure is at least 90 psi. Using a suitable
tool (for example a large flat-blade screwdriver), press the
inboard pad (12) away from the tappets. Check that there
is no dirt, etc. in the gap, and clean if necessary. Then use
13

4.2 ADJUSTER MECHANISM INSPECTION
CAUTION: Follow all safe maintenance practices.
Aside from the normal maintenance schedule, the
adjuster mechanism inspection that follows is also
carried out when the Running Clearance Test (4.1) finds
that the running clearance is too small or too large.
4.2.1 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 cap (stamped metal or plastic
adjuster cap) may be used.

Figure 20 – Backing-Off (Increasing) the Running
Clearance
If the shear adapter fails, you may attempt a second time
with a new (unused) shear adapter.
Note: Always double-check that the spring brake is released
(where applicable) if a shear adapter fails; if this step was
missed, the shear adapter will break off, and it may appear
that the caliper is seized.
In cases where a second failure of the shear adapter
confirms that the adjustment mechanism is seized, the
caliper must be replaced.

Adjuster Cap
Location

Figure 17 – Adjuster Cap Location
37
Cap

23 Adjuster
61 Sheer
Adapter
Tab

37
Cap

Figure 18 – Exploded
View of Adjuster and
Adapter

Tab

Figure 19 – Cap Installed:
Tab Location

For illustration purposes, the exploded view (Figure 18)
shows the adjuster (23) and shear adapter (61) separated.
When using the adjuster mechanism, always have the
shear adapter installed on the adjuster.
4.2.2 Using a 10 mm six-point box-end wrench, turn the
Shear Adapter (61) counterclockwise and listen
for the sound of 3 clicks as the mechanism backsoff (increases) the running clearance. Note: Do not
use an open-ended wrench as this may damage the
adapter. See Figure 20.
CAUTION:
Never turn the adjuster (23) without the shear adapter
(61) installed. The shear adapter is a safety feature and
is designed to prevent excessive torque from being
applied to the adjuster. The shear adapter will fail (by
breaking) if too much torque is applied.
14

Figure 21 – Applying Moderate Applications of the
Brakes: The Wrench Moves Clockwise as the Running
Clearance is Diminished

4.2.3 Where the adjuster mechanism is able to be backed
off normally, position a box-end wrench on the shear
adapter so that it can turn freely clockwise without
coming into contact with parts of the vehicle (See
Figure 21). Make five to ten moderate applications
of the brakes [at about 30 psi (2 Bar)], and observe
that the box-end wrench or socket should turn
clockwise in small increments.

Flat Style Backing Plate “Stamped”
Bendix® BX283™/BA236™
A

B

D

C

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 does not: (a) turn at all; (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.
After completing these wheel-off tests, Bendix recommends
installing a new adjuster cap (lightly grease the outer
sealing edge using white, lithium-based grease to improve
sealing of air in future cap removal) when returning the
brake to service. Ensure that the tab is in the position
shown in Figure 19.

A

New pad thickness (1.181 in.) (30 mm).
BX276: Refer to diagram below for measurement
locations BX275/BX283+: Measure anywhere on
the backing plate surface.

B

New rotor thickness (1.77 in.) (45 mm).
Minimum rotor thickness (1.46 in.) (37 mm).

4.3- 4.4 BRAKE PADS AND ROTORS
CAUTION: Follow all safe maintenance practices.
If electronic wear sensors are present, see Section 5.2.
If dust covers are present, see Section 5.1.
See Figure 23. While pressing down against the pad
retaining bar (11), remove and retain the clip (26),
washer (45), and pin (44). Remove the pad retainer bar
(11). Bendix recommends that these items be replaced with
new (See available kits and parts, Section 5.0).
Follow the steps in Section 4.2 for backing-off the adjuster
mechanism. Slide the caliper inboard then outboard to
permit easy removal of the brake pads.

C Minimum friction material thickness (0.080 in.)
(2 mm) - approximately the thickness of a nickel.
D Minimum thickness of a worn pad (0.43 in.) (11 mm).
Non-Flat Style Backing Plate
“Cast” Bendix® BX276™
Minimum thickness of BX276 Backing Plate is 7 mm (.276 in.)
therefore the overall minimum thickness is 9 mm (.354 in.).
0% Remaining Life

Measurement locations for BX276 brake pads.
Do not measure on raised surfaces.
New
Friction
100% Life

23 mm
30 mm
32 mm

2 mm
9 mm
11 mm

Figure 22 – Pad and Rotor Dimensions
15

See Figure 22 for initial brake pad and rotor dimensions,
as well as minimum acceptable dimensions.
Minor Damage Is Acceptable

Where
a small
amount
of brake
material is
chipped from
the edge

44
Pin
11 Pad Retainer Bar
45 Washer
26 Spring Clip

Figure 23 – Retainer Bar Removal

4.3 INSPECT THE BRAKE PADS
Regular inspection of the brake pads (even for vehicles
that use an electronic wear indicator) is an important part
of vehicle maintenance.
4.3.1 See Figure 22. If the thickness of the friction
material – dimension “C” – is less than 0.080 in.
(2 mm), the pads must be replaced.
Bendix® ADB22X®, ADB22X®-V, and ADB22X®-LT air disc
brakes use 0.35 in. (9 mm) backing plates, so dimension
“D” (the combined pad and backing plate thickness) must
be a minimum of 0.43 in. (11 mm). The minimum thickness
of the ADB22X-LT backing plate is 7 mm (.276 in) where
Bendix requires the measurements be taken from (See
Figure 22). Pad replacement customers are replacing
with BX276.
4.3.2 Check for uneven end-to-end pad wear. If the
difference in wear is greater than 0.080 in. (2 mm),
replace the brake pads and also inspect the guide
pins. (See Section 4.5.)
4.3.3 Compare the thickness of the inboard and outboard
pads of each set. If the difference between the
inboard and outboard pad thickness is greater than
0.138 in. (3.5 mm), replace the brake pads and
inspect the guide pins (See Section 4.5).
If the results of the pad inspections are within the acceptable
range, inspect the pad surface. (See Figure 24.)

16

Major Damage Is Not Acceptable

Section
damaged or
missing

Figure 24 – Brake Pad Surface Inspection
Minor damage at the edges is permitted, but replace the
pads if major damage on the surface of the pad is found.
When replacing brake pads, Bendix strongly
recommends that all the brake pads on an axle
be replaced at one time. See Section 5.1 for the
pad replacement procedure. Also, see the vehicle
manufacturer’s recommendations found in the operator’s
manual.
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. In all cases, use
brake pads with the type of backing plate and lining material
originally supplied by the vehicle manufacturer.
CAUTION: When replacing brake pads and rotors,
use only Bendix® brand replacement pads and rotors
and/or those approved by the OEM. Non-approved
replacement disc pads or rotors can cause excessive
wear on brake components; can increase the risk of rotor
cracking; may reduce levels of safety; and invalidate the
brake warranty.

4.4 INSPECT THE ROTOR
CAUTION: Follow all safe maintenance practices.
Identify if the rotor is a Bendix® Splined Disc®, or Bendix®
brand conventional rotor (See Section 1.03). Rotors should
be inspected regularly (See Section 2.0 for recommended
inspection schedule) and at each pad change.
4.4.1 Measure the thickness of the brake rotor at the
thinnest point (Dimension “B” in Figure 22). Avoid
measuring near the edge of the rotor as minor burrs
may result in an inaccurate measurement. For
Bendix brand rotors, replace the rotor when
the minimum thickness of 1.46 in. (37 mm) is
reached. For other brands of rotors, refer to the
rotor manufacturer’s guidelines.

4.4.2 Inspect the rotor surface. See Figure 25. The type
of rotor, and also the size, depth, and direction of
the imperfections, must all be considered.

NOTE: If surface wear conditions F through J are
in the permitted range, the rotor is still usable until
it reaches the minimum acceptable thickness for the
rotor manufacturer’s guidelines.

H

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

Rotor
Friction
Surface
Width “f”

Area
F

Area
H

f

Area G
G
Cracks reaching
either edge of the
rotor
are not
acceptable
for either
type of
rotor

• For standard Bendix® brand rotors,
cracks running in a radial direction – like
spokes of a wheel (see Area H) – less
than 0.06 in. (1.5 mm) deep or wide are
acceptable if they do not reach either
edge (see Area G). Cracks are only
acceptable if the length of the crack is
less than 75% of dimension “f” (the width
of the rotor contact area).

Area J

• For Bendix® Splined Disc® rotors,
radial cracks are only acceptable if they
are less than 0.04 in. (1.0 mm) deep
or wide and if they do not reach either
edge (see Area G). Crack lengths must
be less than 75% of dimension “f” (the
width of the rotor contact area).

J
Circumferential
grooves, as in Area
J, are acceptable
if less than 0.06 in.
(1.5 mm) deep.

In addition, follow the
recommendations of
the vehicle and rotor
manufacturer.