ISO 4251-2:2019 農業用トラクター、トレーラー、機械用のコード指定斜めタイヤ（プライ定格マーク付きシリーズ）—パート2：タイヤ定格荷重 | ページ 2

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 ).

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This document was prepared by ISO/TC 31, Tyres, rims and valves, SC 5, Agricultural tyres and rims.

This eighth edition cancels and replaces the seventh edition (ISO 4251-2:2017) which has been technically revised. The main changes compared to the previous edition are as follows:

• information already contained in other International Standards was removed and replaced with normative references to those standards;
• radial tyres marked with ply rating and with reference speed of 10 km/h were deleted since obsolete and this document was restricted to code designated diagonal tyres (marked with PR) for agricultural tractors trailers and machines;
• the title of this document was revised accordingly;
• the document was aligned with other International Standards developed by SC 5 and with existing regulations;
• equivalence of tyre load carrying capacities in case of tyre marked with speed symbol A6 (corresponding to previous load carr y ing capacities of tyres marked with PR only) and that of tyres marked with speed symbol A8 was introduced, together with the possibility of a double marking (supplementary service description);
• load variations with speed and for specific applications were added;
• s ome additional PR versions were added with the corresponding markings of the service description.

1 Scope

This document establishes the load ratings of the diagonal code designated (ply rating marked series) tyres for agricultural tractors, trailers and machines.

Tyre designation and dimensions, and approved rim contours are given in ISO 4251-1.

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.

3 Terms and definitions

For the purposes of this document the terms and definitions given in ISO 4223-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

Bibliography