ISO 4000-1:2024

Overview

ISO 4000-1:2024 - "Passenger car tyres and rims - Part 1: Tyres (metric series)" is the thirteenth edition of the International Standard that defines how metric-series passenger car tyres are designated, dimensioned and rated for load and speed. The standard establishes consistent rules for tyre size notation, construction codes, rim diameter coding, marking and key performance indicators (load index, speed symbol), plus procedures for dimension measurement and inflation guidance. This edition updates the 2021 version and adds provisions for high load capacity tyres and new harmonized load indices.

Key topics and requirements

• Designation and size format: Specifies the structure of tyre markings (e.g., nominal section width / aspect ratio / construction code / nominal rim diameter) and rules for section width and aspect ratio values.
• Construction codes: Standardized codes for tyre construction such as B (bias-belted), D (diagonal), R (radial), RF (radial run-flat) and the ZR/ZRF variants for high-speed tyres.
• Rim diameter coding: Nominal rim diameter codes and guidance for new-concept rims to avoid mis-mounting.
• Service description and markings: Rules for indicating load index, speed symbol (and speed category), and additional markings (TUBELESS, XL/REINFORCED/EXTRA LOAD, HL for high‑load tyres, LL for light‑load, T for temporary spare, P for passenger car designation).
• Dimensions and measurement: Methods to calculate design tyre section width, height, overall diameter, and maximum/minimum grown dimensions when mounted on measuring rims; rounding rules and measuring rim codes.
• Performance parameters: Load-carrying capacities (see Annex B load indices), minimum inflation pressure guidance (Annex C), and inflation pressure procedures.
• Supporting material: Informative and normative annexes with guideline values, load index tables, and other size-marking systems.

Applications and users

ISO 4000-1:2024 is essential for:

• Tyre manufacturers - to mark products correctly, define dimensions and certify load/speed ratings.
• Rim and wheel designers - to match tyre/rim interfaces and avoid mounting errors.
• Vehicle OEMs and aftermarket installers - for correct tyre selection, replacement and spare tyre specification.
• Testing laboratories and certification bodies - to measure tyre dimensions, validate load indices and verify conformity.
• Regulators and marketers - to harmonize labelling, safety information and technical documentation.

Using ISO 4000-1 helps ensure interchangeability, safety, global compliance and clearer tyre sizing information across markets.

Related standards

• ISO 3877-1 - Tyre terminology (equivalent terms)
• ISO 4223-1 - Definitions of tyre industry terms
• ISO 16992 - Spare unit substitutive equipment (SUSE) and run-flat definitions

Keywords: ISO 4000-1:2024, passenger car tyres, metric series, tyre dimensions, load index, speed symbol, tyre marking, rim diameter, tyre standards.