TP-15140
Issued 11-15

Cable Strain Relief Guidelines for
Meritor WABCO Trailer ABS/RSS

Technical Bulletin
How to Obtain Additional Maintenance,
Service and Product Information
Issued
1TP-15140
Technical
11-15
Bulletin

If you have any questions about the material covered in this
technical bulletin, contact the Meritor OnTrac™ Customer Call
Center at 866-OnTrac1 (668-7221), or visit our website:
meritorwabco.com.

Introduction
This technical bulletin provides correct cable strain relief guidelines
for Meritor WABCO trailer ABS/RSS cables. It is important that
cabling follow good strain relief practices to ensure maximum
performance and durability. Failure to provide adequate strain relief
on the cables can result in future maintenance that is not covered
under warranty.
Strain relief is defined as a small amount of slack in the cable at the
area of connection. This lack of cable tension allows for slight
movement of the cable during times when components of the
suspension and air system may be in motion. A small amount of
slack also eases access to other system components.
A taut cable can affect the lifespan of the cable. Cables without
adequate strain relief can potentially stress a cable connection
enough that moisture could intrude. Unnecessary wear at bend
points can be the result of a cable under tension.
Cable strain relief is a universal practice. It applies to all Meritor
WABCO product lines from Anti-Lock Brake (ABS) systems to Roll
Stability Systems (RSS).

Cable Strain Relief Guidelines
Excess Cable Length
In cases where the length of cable exceeds what is required, the
excess must be bundled in an efficient manner. It should not be
draped or wrapped around components or left unsecured. Any slack
remaining in the cable once the connections are made can be
gathered up in a Z-shaped loop. Do not coil the cable and pinch into
a bowtie or dog-bone shape. All cable zip ties should be tightened in
a manner only to the extent that the cable is held sufficiently in
place. Fasten the excess cable to an area that is free of sharp edges
and moving components.

Meritor WABCO has many lengths of cables available so it is a best
practice to obtain a length that best suits the requirements of the
installation.

Strain Relief at the ECU — Bracket Mounting
Meritor WABCO recommends that cable connections to a
component, such as an ECU valve assembly, display a visible
amount of slack in the cable up to the first tie or clip that secures
the cable to trailer structure or air line. This first anchor point should
be a minimum 6-inches (152 mm) of cable length from the cable/
component connection and maximum of 12-inches (305 mm). This
applies to all sensor, power, valve and GIO cables.
Regardless of whether zip ties or cable clips are used, cables should
be secured at intervals not greater than 18-inches (457 mm) to
avoid cable vibration.
Ideally, cables should be affixed to the rigid structure of the trailer. A
good rule of thumb is to have the bend of the cable, also known as
bend radius, be greater than or equal to ten times the diameter of
the cable. If the cable is 1/4-inch (6.35 mm) in diameter, then the
bend should be a minimum of 2-1/2-inches (64 mm). Refer to
Figure 1 for RSS 2M, Figure 2 for 4S/2M ABS and Figure 3 for
2S/1M ABS.

Figure 1

Z

Z = ZIP TIE

R
Z
R

D
D

R 욷 10 X D
2.2

Bend radius (R) equal to or greater than
10 times cable diameter (D).
First fastener must be a minimum
6-inches (152 mm) and a maximum of 12-inches
(305 mm) from connector.

2.2

Z

1

R

R 욷 10 X D

4011413a

RSS 2M
Figure 1

Figure 2

Z = ZIP TIE

R

R
Z

Z
D

D
R 욷 10 X D

R 욷 10 X D

Bend radius (R) equal to or greater than
10 times cable diameter (D).
First fastener must be a minimum 6-inches
(152 mm) and a maximum of 12-inches (305 mm) from connector.

4011414a

ABS 4S/2M
Figure 2

TP-15140
Issued 11-15
Page 2

Copyright Meritor, Inc., 2015

(16579)
Printed in USA

Figure 3

Z = ZIP TIE

R
Z
D

YE 2/6

YE 1/4

R 욷 10 X D

Bend radius (R) equal to or greater than
10 times cable diameter (D).
First fastener must be a minimum 6-inches
(152 mm) and a maximum of 12-inches (305 mm)
from connector.
4011441a

ABS 2S/1M
Figure 3

Strain Relief at the ECU — Tank Mounting
It is necessary that cable connections to a component, such as an
ECU valve assembly, display a visible amount of slack in the cable
up to the first tie or clip that secures the cable to trailer structure or
air line. This first anchor point should be a minimum 6-inches
(152 mm) of cable length from the cable/component connection and
a maximum of 12-inches (305 mm). This applies to all sensor,
power, valve and GIO cables. Regardless of whether zip ties or cable
clips are used, cables should be secured at intervals not greater
than 18-inches (457 mm) to avoid cable vibration.

Ideally, cables should be affixed to the rigid structure of the trailer.
However, structure is not always available on tank-mounted
installations. In these cases, securing the cable may be
accomplished by fastening the cable to nearby air lines. It is
important to note that cables should be secured only to the extent
that the cable is held sufficiently in place. Refer to Figure 4 for
4S/2M ABS, Figure 5 for 2S/1M ABS, and Figure 6 for RSS 1M.

Figure 4

4011414b

CORRECT POWER AND GIO/MODULATOR CABLE STRAIN RELIEF FOR ABS 4S/2M
Figure 4

(16579)
Printed in USA

Copyright Meritor, Inc., 2015

TP-15140
Issued 11-15
Page 3

Figure 5

YE 2/6

YE 1/4

4011441c

CORRECT POWER CABLE STRAIN RELIEF FOR ABS 2S/1M
Figure 5

Figure 6

4011894a

CORRECT CABLE STRAIN RELIEF FOR RSS 1M
Figure 6

Sensor Extension Cables at the ECU
On valves that are tank mounted with no trailer structure nearby, or
have remote-mounted cables, the sensor extension cables are
attached to the air lines. Cable clips are preferred to zip ties. It is
important to remember that cables should be fastened in a manner
where the cable is secured enough where the cable will not move or
chafe against what it is mounted to. A small amount of slack should
be present to ensure that the cables do not become taut after
installation or the servicing of components. Figure 7 and Figure 8
illustrate correct amount of slack in the sensor extension cables and
correct attachment to the air delivery lines for ABS ECUs.

TP-15140
Issued 11-15
Page 4

Copyright Meritor, Inc., 2015

(16579)
Printed in USA

Figure 7

Figure 9

SENSOR CABLE STRAIN
RELIEF FOR ABS 2S/1M
4012335a
Figure 7

4011892a
Figure 8

ZIP TIE PLACEMENT
Figure 9

Once anchored to the ECU assembly, secure the cables to the air
delivery lines using zip ties or cable clamps. Figure 10.
Figure 10

SENSOR CABLE STRAIN RELIEF
FOR ABS 4S2M

4005457d

Figure 8

On RSS 1M valves that are tank mounted, there are small channels
on the valve assembly that are specifically for securing the power
and sensor extension cables. Once the cables have been installed
on the ECU and the securing clips pushed into the locked position,
use zip ties to anchor the cables to the valve. Slide the zip tie
through the valve assembly’s channel and then secure the cable.
Figure 9.

4011894c

ZIP TIE PLACEMENT
Figure 10

RSS 2M ECU valve assemblies have a zip tie channel on the valve
assembly to secure the power cable. Slide the zip tie through the
valve assembly’s channel and then secure the power cable. When
installing a RSS 2M ECU valve assembly, secure the sensor
extension cables by fastening them to nearby air lines. It is
important to note that an appropriate amount of slack is left in the
cables and that cables are secured only to the extent that the cable
is held sufficiently in place. Figure 11.

(16579)
Printed in USA

Copyright Meritor, Inc., 2015

TP-15140
Issued 11-15
Page 5

Placement of Cables on Air Lines — Cable-to-Cable
Connections

Figure 11

It is important to ensure all cable-to-cable connections maintain
good strain relief. Cable restraints must be placed between two- and
four-inches (51-102 mm) from the cable connector to ensure
correct strain relief. Regardless of whether zip ties or cable clips are
used, cables should be secured at intervals not greater than
18-inches (457 mm) to avoid cable vibration. Refer to Figure 13 for
air line attachment and Figure 14 for axle attachment.
Figure 13

3"
(76 MM)

3"
(76 MM)

ZIP TIES ON AIR LINES
4012336a

4011893a

Figure 13

RSS 2M ZIP TIE PLACEMENT
Figure 11

Figure 14

SENSOR
CABLE

Placement of Cables and Fittings at the ECU

3"
(76 MM)

Routing of air lines near the ECU assembly requires careful
consideration. Selection of the optimum fitting also has an impact
on strain relief. It can affect the integrity of the connection’s sealing
capability and, as shown in Figure 12, the style of fitting can
adversely impact strain relief. Correct positioning of the cables is
shown in Figure 8.
Figure 12

ZIP TIES ON AXLE

4011417a

Figure 14

INCORRECT ROUTING

4012365a

Figure 12

Meritor WABCO Vehicle Control Systems
2135 West Maple Road
Troy, MI 48084-7121 USA
866-OnTrac1 (668-7221)
meritorwabco.com

Information contained in this publication was in effect at the time the publication was approved for printing and is subject to
change without notice or liability. Meritor WABCO reserves the right to revise the information presented or to discontinue the
production of parts described at any time.
Copyright 2015
Meritor, Inc.
All Rights Reserved

Printed in USA

TP-15140
Issued 11-15
(16579)