ISO 11749:2023

Belt drives — V-ribbed belts for the automotive industry — Fatigue test

This document specifies a dynamic test method for the quality control of V-ribbed belts (PK profile) which are used predominantly for accessory drive applications in the automotive industry. The dimensional characteristics of the belts and of corresponding pulleys are the subject of ISO 9981.

Transmissions par courroies — Courroies striées pour la construction automobile — Essai de fatigue

General Information

• Status: Published
• Publication Date: 01-Nov-2023
• ICS: 21.220.10 - Belt drives and their components
• ICS: 43.060.10 - Engine block and internal components
• Technical Committee: ISO/TC 41/SC 1 - Friction
• Drafting Committee: ISO/TC 41/SC 1 - Friction
• Current Stage: 6060 - International Standard published
• Start Date: 02-Nov-2023
• Due Date: 15-Nov-2023
• Completion Date: 02-Nov-2023

Relations

• Revises: ISO 11749:2014 - Belt drive — V-ribbed belts for the automotive industry — Fatigue test
• Effective Date: 06-Jun-2022

Overview - ISO 11749:2023 (V-ribbed belts fatigue test)

ISO 11749:2023 specifies a dynamic fatigue test method for quality control of V-ribbed belts (PK profile) used mainly in automotive accessory drives. The standard defines test machine layouts (two-, three- and four-pulley configurations), test conditions, measurement requirements and reporting details to determine belt life under specified load, speed and tensioning conditions. Dimensional characteristics of belts and pulleys are covered separately by ISO 9981.

Key topics and technical requirements

• Test principle: Dynamic endurance testing on robust test machines to determine when a belt fails to meet agreed performance criteria (power transmission, slip, retensioning cycles).
• Machine layouts: Acceptable configurations for two-, three- and four-pulley test rigs, with alignment tolerances and guidance on which belt lengths fit each layout.
• Tensioning methods: Procedures for tests with fixed belt tensioning force and with constant belt tensioning force (newly clarified in the 2023 edition).
• Pulley specifications:
  • Test pulleys made of steel with surface hardness ~55 HRC.
  • Pulley groove surface roughness R < 3.2 µm.
  • Groove geometry examples: groove pitch 3.56 mm and groove angle 40° (Table 2 provides detailed dimensions and tolerances).
• Measurement accuracy: Means to determine belt slip to ±0.1% and limits for radial/axial runout (≤ 0.25 mm TIR).
• Environmental control: Specified test-room temperature range and requirement to record mean temperature during testing.
• Documentation: Required test report items (test conditions, tensioning, slip, retensioning, life in hours, etc.).

Practical applications and users

Who uses ISO 11749:2023:

• Automotive belt manufacturers - to validate product durability and maintain quality control for accessory drive belts.
• OEMs and Tier‑1 suppliers - to specify belt acceptance criteria and ensure compatibility with vehicle accessory systems.
• Test laboratories and R&D centers - to conduct standardized fatigue tests, compare designs and certify belts to customer requirements.
• Component designers and quality engineers - to evaluate belt/pulley interactions and inform maintenance/service-life expectations.

Practical benefits:

• Consistent, repeatable method to assess V-ribbed belt fatigue life.
• Basis for supplier agreements on minimum acceptable life, retensioning cycles and transmitted power.
• Facilitates comparability between belt designs and material/process changes.

Related standards

• ISO 9981 - Dimensional characteristics of V-ribbed belts and corresponding pulleys (referenced for groove profiles and dimensional design).
• ISO 254 - Surface roughness definitions and measurement methods (used for pulley surface roughness guidance).

Keywords: ISO 11749:2023, V-ribbed belts, fatigue test, PK profile, belt drives, automotive accessory drive, pulley dimensions, ISO 9981.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 11749
Third edition
2023-11
Belt drives — V-ribbed belts for the
automotive industry — Fatigue test
Transmissions par courroies — Courroies striées pour la construction
automobile — Essai de fatigue
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 1
5 Principle . 2
6 Apparatus . 7
7 Test room conditions . .9
8 Test method .10
8.1 Test conditions . 10
8.1.1 Test with fixed belt tensioning force . 10
8.1.2 Test with constant belt tensioning force . 10
8.2 Procedure . 11
8.2.1 Preparation . 11
8.2.2 Test . . . 11
8.2.3 Retensioning .12
9 Test report .12
Bibliography .14
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 41, Pulleys and belts (including veebelts),
Subcommittee SC 1, Friction.
This third edition cancels and replaces the second edition (ISO 11749:2014), which has been technically
revised.
The main changes are as follows:
— addition of Table 1 with symbols;
— addition of the test condition with constant belt tensioning force in 8.1.2 and 8.2.1.3;
— change in pulley surface roughness R to < 3,2 μm;
a
— revision of test pulley dimensions (Table 2).
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
INTERNATIONAL STANDARD ISO 11749:2023(E)
Belt drives — V-ribbed belts for the automotive industry —
Fatigue test
1 Scope
This document specifies a dynamic test method for the quality control of V-ribbed belts (PK profile)
which are used predominantly for accessory drive applications in the automotive industry.
The dimensional characteristics of the belts and of corresponding pulleys are the subject of ISO 9981.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
For the purpose of this document, the symbols given in Table 1 apply.
Table 1 — Symbols
Symbols Designation Unit
b effective line differential mm
e
d checking ball or rod diameter mm
B
d effective diameter mm
e
d effective diameter of driving and driven pulleys mm
e1
d effective diameter of idler pulley mm
e2
d pitch diameter mm
p
d outside diameter of reverse bending idler pulley mm
r3
e groove pitch mm
f lateral distance mm
F belt tensioning force N
g additional slip %
i rotational frequency ratio at measurement of the additional slip —
f
i rotational frequency ratio at the initial —
o
k standard value to calculate belt tensioning force N/kW
K diameter over balls or rods mm
M torque load Nm
a
Rotations per minute.
TTabablele 1 1 ((ccoonnttiinnueuedd))
Symbols Designation Unit
n number of grooves —
a
n final rotational speed of the driven shaft r/min
f
a
n initial rotational speed of the driven shaft r/min
o
a
N driver speed r/min
a
N final rotational speed of the driving shaft r/min
f
a
N initial rotational speed of the driving shaft r/min
o
P specified power kW
s
r radius at the groove root mm
b
r radius at the groove tip mm
t
R surface roughness µm
a
2x position of the ball or rod to groove tip mm
α groove angle °
a
Rotations per minute.
5 Principle
Determination of the performance of a belt under specified conditions on a two-, three-, or four-pulley
test machine is as described in Clause 6.
The shortest V-ribbed belt which can be tested on the four-pulley test machine (see Figures 1 and 2) is
approximately 1 000 mm. Belts with lengths between 800 mm and 1 000 mm inclusive can be tested
on the three-pulley test machine (see Figure 3). Shorter belts should be tested on the two-pulley test
machine (see Figure 4) as described in 8.2.1.2.
A number of conditions with fixed belt tensioning force shall be agreed between the manufacturer and
user, including the power to be transmitted and the number of times the belt can be retensioned.
The minimum acceptable life, in hours, shall be agreed between the manufacturer and users.
Belt failure occurs when the belt no longer satisfies the agreed conditions.
Key
1 driving pulley
2 driven pulley (power-absorption unit)
3 idler pulley, set in slide
4 reverse bending idler pulley
5 direction of adjustment of driving and driven pulley
6 direction of rotation with fixed belt tensioning force
7 belt tensioning force applied to the idler pulley
8 direction of adjustment of idler pulley assembly and its support
a Equal (=), the angle as shown by Figure 1 is specified for the initial test layout and may change slightly with
retensioning during the course of the test.
Figure 1 — Four-pulley test machine layout (fixed belt tensioning force)
Key
1 driving pulley
2 driven pulley (power-absorption unit)
3 idler pulley, set in slide
4 reverse bending idler pulley
5 direction of adjustment of driving and driven pulley
6 direction of rotation with constant belt tensioning force
7 belt tensioning force applied to the idler pulley
8 direction of adjustment of idler pulley assembly and its support
a Equal (=), the angle as shown by Figure 2 is specified for the initial test layout and may change slightly with
retensioning during the course of the test.
Figure 2 — Four-pulley test machine layout (constant belt tensioning force)
Key
1 driving pulley
2 driven pulley (power-absorption unit)
3 idler pulley, set in slide
4 direction of adjustment of driving and driven pulley
5 direction of rotation
6 belt tensioning force applied to the idler pulley
7 direction of adjustment of idler pulley assembly and its support
The belt, mounted on the test pulleys shall be aligned to within ±0,25° in relation to the plane through the centre of
each pulley.
a
45° is specified for the initial test layout and may change slightly with retensioning during the course of the test.
Figure 3 — Three-pulley test machine layout
Key
1 driving pulley
2 driven pulley (power-absorption unit)
3 direction of adjustment of the movable pulley (method of locking in place)
4 belt tensioning force applied to the movable pulley
The belt, mounted on the test pulleys, can be aligned to within ±0,25° in relation to the plane through the centre of
each pulley.
Figure 4 — Two-pulley test machine layout
The actual configuration of the tip profile can lie anywhere between the maximum and minimum indicated. Any
configuration shall have a transitional radius, r , corresponding to a 30° minimum arc tangent to the groove side
t
wall (in accordance with ISO 9981).
Figure 5 — Cross-section of pulley grooves
Radial an
...