ISO 789-2:2018

Agricultural tractors - Test procedures - Part 2: Rear three-point linkage lifting capacity

ISO 789-2:2018 specifies test procedures for determining the lifting capacity of rear-mounted three-point linkage systems: a) the maximum vertical force which can be exerted by the hydraulic lift at the lower hitch points throughout their full range of movement; b) the maximum vertical force which can be exerted by the hydraulic lift, at a point 610 mm to the rear of the hitch points on a frame attached to the three-point linkage, throughout its full range of movement. NOTE 1 A static test provides an adequate comparison between tractors. The test results are used only as a means of comparing tractors and not as a way of recommending the size of an implement which can be carried by the tractor. NOTE 2 This test procedure can be used to determine the lifting capacity of front-mounted three-point hitch systems.

Tracteurs agricoles — Méthodes d'essai — Partie 2: Capacité de relevage de l'attelage trois points arrière

General Information

• Status: Published
• Publication Date: 21-Feb-2018
• ICS: 65.060.10 - Agricultural tractors and trailed vehicles
• Technical Committee: ISO/TC 23/SC 2 - Common tests
• Drafting Committee: ISO/TC 23/SC 2 - Common tests
• Current Stage: 9093 - International Standard confirmed
• Start Date: 29-Jul-2024
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 789-2:1993 - Agricultural tractors - Test procedures - Part 2: Rear three-point linkage lifting capacity
• Effective Date: 28-Feb-2009

Overview

ISO 789-2:2018 specifies standardized test procedures to determine the lifting capacity of rear-mounted three-point linkage systems on agricultural tractors. It defines how to measure the maximum vertical force the tractor’s hydraulic lift can exert at the lower hitch points and at a point 610 mm behind the hitch on a coupled frame. The standard is intended for comparative, static testing of tractors (and can also be applied to front-mounted three‑point hitches), not for sizing implements.

Key topics and technical requirements

• Scope of measurement
  • Maximum vertical force at the lower hitch points throughout the full range of movement.
  • Maximum vertical force at a point 610 mm to the rear of the hitch on a frame attached to the linkage.
• Test method
  • Apply a vertical, measurable external load and record lifting force and hydraulic pressure at a minimum of six points (including both extremes) across the lift range.
  • Correct measured forces to a hydraulic pressure equal to 90% of the relief valve pressure; the lowest corrected value is reported as the maximum vertical force for the full range.
• Setup and adjustments
  • Secure the unballasted tractor horizontally so tyres/suspension are not deflected.
  • Adjust linkage according to ISO 730 power range and lower hitch point height; upper link length set so mast is vertical when lower links are horizontal.
  • Throttle lever set fully open during tests.
• Environmental and hydraulic conditions
  • Hydraulic fluid as recommended by manufacturer; temperature at test start 65 °C ± 5 °C (or state measured temperature if not achievable).
  • Ambient temperature 23 °C ± 7 °C; atmospheric pressure should not be less than 96.6 kPa.
• Measurement units and tolerances
  • Force, pressure, distance, rotational speed and other tolerances are specified (e.g., force ±1%, pressure ±2%).
• Reporting
  • Test report must include tractor selection, running‑in, adjustments, measured values, any repairs and deviations.

Applications and who uses it

ISO 789-2 is used by:

• Tractor manufacturers for product development and performance validation.
• Independent test laboratories and certification bodies conducting comparative lifting-capacity tests.
• Agricultural OEMs and implement designers evaluating compatibility and comparative performance.
• Procurement teams and technical specifiers comparing tractor hydraulic lift performance.

Practical benefits include consistent, repeatable comparison of three-point linkage lifting capacity, improved product transparency, and harmonized testing across markets.

Related standards

• ISO 730 - Rear-mounted three‑point linkage categories (used for linkage setup).
• ISO 789-13 - Vocabulary and specimen test report (reporting format).
• ISO 3448 - Viscosity classification (hydraulic fluid identification).

Keywords: ISO 789-2, three-point linkage, lifting capacity, agricultural tractors, test procedures, rear three-point hitch, hydraulic lift, lifting force, tractor testing.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 789-2
Fourth edition
2018-02
Agricultural tractors — Test
procedures —
Part 2:
Rear three-point linkage lifting
capacity
Tracteurs agricoles — Méthodes d'essai —
Partie 2: Capacité de relevage de l'attelage trois points arrière
Reference number
©
ISO 2018
© ISO 2018
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Measurement units and tolerances . 2
5 General requirements . 2
5.1 Selection. 2
5.2 Running-in and preliminary adjustments . 2
5.3 Manufacturer's instructions . 2
5.4 Repairs . 2
5.5 Preliminary information . 2
5.6 Hydraulic fluid . 3
5.7 Ambient conditions . 3
6 Test procedures . 3
6.1 Common procedures . 3
6.1.1 Secure . 3
6.1.2 Adjustment . . . 3
6.1.3 Throttle lever . 4
6.1.4 Measured maximum performance . 4
6.2 Lift at lower hitch points . 5
6.3 Lift on coupled frame . 6
7 Test report . 6
Bibliography . 7
Foreword
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electrotechnical standardization.
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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
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URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 23, Tractors and machinery for agriculture
and forestry, Subcommittee SC 2, Common tests.
This fourth edition cancels and replaces the third edition (ISO 789-2:1993), which has been technically
revised for the technical harmonization with OECD Code 2: February 2017.
A list of all the parts in the ISO 789 series can be found on the ISO website.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 789-2:2018(E)
Agricultural tractors — Test procedures —
Part 2:
Rear three-point linkage lifting capacity
1 Scope
This document specifies test procedures for determining the lifting capacity of rear-mounted three-
point linkage systems:
a) the maximum vertical force which can be exerted by the hydraulic lift at the lower hitch points
throughout their full range of movement;
b) the maximum vertical force which can be exerted by the hydraulic lift, at a point 610 mm to the
rear of the hitch points on a frame attached to the three-point linkage, throughout its full range of
movement.
NOTE 1 A static test provides an adequate comparison between tractors. The test results are used only as a
means of comparing tractors and not as a way of recommending the size of an implement which can be carried by
the tractor.
NOTE 2 This test procedure can be used to determine the lifting capacity of front-mounted three-point hitch
systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 730:2009, Agricultural wheeled tractors — Rear-mounted three-point linkage — Categories 1N, 1, 2N,
2, 3N, 3, 4N and 4
ISO 730:2009/Amd 1:2014, Agricultural wheeled tractors — Rear mounted three-point linkage – Categories
1N, 1, 2N, 2, 3N, 3, 4N and 4 — Amendment 1
ISO 789-13:2018, Agricultural tractors — Test procedures — Part 13: Vocabulary and specimen test report
ISO 3448:1992, Industrial liquid lubricants — ISO viscosity classification
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 789-13 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
4 Measurement units and tolerances
The following units and tolerances apply to the maximum value measured:
— rotational frequency, in revolutions per minute (r/min): ± 0,5 %;
— time, in seconds (s): ± 0,2 s;
— distance, in metres or millimetres (m or mm): ± 0,5 %;
— force, in newtons (N): ± 1 %;
— mass, in kilograms (kg): ± 0,5
...