ISO 12046:2025

Synchronous belt drives - Automotive belts - Determination of physical properties

This document specifies test methods for determining the physical properties of synchronous belts used in driving engine parts, such as camshafts, fuel injection pumps, balancing shafts. These test methods are intended to provide a means of characterizing synchronous belt properties for belts which are evaluated and qualified by dynamic laboratory and field testing.

Transmissions synchrones par courroies — Courroies pour la construction automobile — Détermination des caractéristiques physiques

La présente Norme internationale spécifie des méthodes d'essai pour déterminer les caractéristiques physiques des courroies synchrones utilisées pour l'entraînement des pièces de moteurs, telles que les arbres à cames, les pompes à injection et les arbres d'équilibrage de vilebrequin. Ces méthodes d'essai sont destinées à fournir un moyen permettant de déterminer les caractéristiques des courroies synchrones qui sont évaluées et qualifiées par des essais dynamiques en laboratoire et par des essais en conditions réelles.

General Information

• Status: Published
• Publication Date: 08-Jan-2025
• ICS: 21.220.10 - Belt drives and their components
• ICS: 43.060.10 - Engine block and internal components
• Technical Committee: ISO/TC 41/SC 4 - Synchronous belt drives
• Drafting Committee: ISO/TC 41/SC 4 - Synchronous belt drives
• Current Stage: 6060 - International Standard published
• Start Date: 09-Jan-2025
• Due Date: 02-Apr-2025
• Completion Date: 09-Jan-2025

Relations

• Revises: ISO 12046:2012 - Synchronous belt drives - Automotive belts - Determination of physical properties
• Effective Date: 28-Oct-2023

Overview

ISO 12046:2025 - Synchronous belt drives - Automotive belts - Determination of physical properties - specifies standardized test methods to characterize the physical properties of automotive synchronous (timing) belts used to drive engine parts (camshafts, fuel‑injection pumps, balancing shafts). The tests support laboratory and field qualification by providing repeatable measurements independent of tooth profile.

Key topics and technical requirements

• Scope of tests: hardness of rubber core; tensile strength; fabric adhesion; tension‑cord adhesion; tooth shear; resistance to high/low temperature, oil, ozone and water.
• Test environment & specimen conditioning: standard laboratory conditions at 25 ± 5 °C, 65 ± 20 % RH, atmospheric pressure 86–106 kPa; specimens tested ≥16 h after vulcanization and conditioned ≥1 h under standard conditions.
• Specimen sizes and mounting: minimum specimen lengths specified (e.g., 100 mm for hardness/fabric tests; 250 mm for tensile tests); endless belt or cut specimens allowed.
• Tensile test procedure: endless‑belt mounting on two free‑rotating flat pulleys (diameter 100–175 mm); applied extension speed 50 ± 5 mm/min; tensile strength taken as half the measured value for endless specimens (or the smaller of two cut specimens).
• Rounding and reporting: results rounded per Table 2 rules (e.g., tensile strength to nearest 100 N); test report must include tooth count/pitch/profile, materials, production code, environmental conditions, apparatus and reference to ISO 12046:2025.
• Normative references: incorporates ISO 48‑2 (rubber hardness), ISO 1817 (effect of liquids on rubber), and ISO 5288 (synchronous belt vocabulary).

Applications and users

ISO 12046:2025 is intended for:

• Automotive component manufacturers and suppliers performing belt qualification and quality control.
• Test laboratories conducting material characterization and failure analysis.
• OEM engineering teams specifying belt performance for engine timing and accessory drives.
• Certification bodies and procurement teams requiring consistent, comparable test data for supplier evaluation.

Practical uses include comparing belt formulations, verifying adhesion and cord integrity, assessing environmental resistance (oil/ozone/water/temperature) and supplying objective data for dynamic laboratory and field validation.

Related standards

• ISO 48‑2 - Rubber hardness (Shore A, IRHD)
• ISO 1817 - Effect of liquids on rubber
• ISO 5288 - Synchronous belt drives - Vocabulary

Using ISO 12046:2025 ensures repeatable, internationally harmonized measurements of synchronous belt physical properties, improving reliability of belt selection, design validation and supplier qualification in automotive powertrain applications.

Standards Content (Sample)

International
Standard
ISO 12046
Third edition
Synchronous belt drives —
2025-01
Automotive belts — Determination
of physical properties
Transmissions synchrones par courroies — Courroies pour la
construction automobile — Détermination des caractéristiques
physiques
Reference number
© ISO 2025
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
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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Test methods . 1
6 General conditions for testing . 2
6.1 Standard environmental conditions .2
6.2 Standard conditions of test specimens .2
6.3 Rounding off the test results .2
6.4 Test report .2
7 Static property tests . 3
7.1 Test for hardness of rubber core .3
7.1.1 Test specimens .3
7.1.2 Procedure .3
7.1.3 Expression of results .3
7.2 Tensile strength test .3
7.2.1 Test specimens .3
7.2.2 Procedure .3
7.2.3 Expression of results .4
7.3 Fabric adhesion test .4
7.3.1 Test specimens .4
7.3.2 Procedure .4
7.3.3 Expression of results .4
7.4 Tension-cord adhesion test.5
7.4.1 Test specimens .5
7.4.2 Procedure .6
7.4.3 Expression of results .6
7.5 Tooth-shear test . .6
7.5.1 Test specimens .6
7.5.2 Apparatus .6
7.5.3 Tooth-shearing chip .7
7.5.4 Procedure .9
7.5.5 Expression of results .9
7.6 Test for resistance to high temperature .9
7.6.1 Test specimens .9
7.6.2 Procedure .10
7.7 Test for resistance to low temperature .10
7.7.1 Test specimens .10
7.7.2 Procedure .10
7.8 Test for resistance to oil .10
7.8.1 Test specimens .10
7.8.2 Procedure .10
7.9 Test for resistance to ozone .10
7.9.1 Test specimens .10
7.9.2 Procedure .10
7.10 Test for resistance to water .10
7.10.1 Test specimens .10
7.10.2 Procedure .11

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 41, Pulleys and belts (including veebelts),
Subcommittee SC 4, Synchronous belt drives.
This third edition cancels and replaces the second edition (ISO 12046:2012), which has been technically
revised.
The main changes are as follows:
— Clause 2 h
...