Overview
ISO 15222:2025 - Truck and bus tyres - Method for measuring relative wet grip performance - Loaded new tyres defines a standardized test procedure for measuring the relative wet grip braking performance of new commercial vehicle tyres on a wet‑paved surface. The standard specifies methods to reduce test variability by using a reference tyre and applies to truck and bus tyres used on commercial vehicles. It excludes tyres with traction devices (e.g., studded tyres) and professional off‑road tyres. This is the third edition and replaces ISO 15222:2021 with updated reference tyres and revised track characterisation.
Key topics and technical requirements
- Test scope and definitions: Key terms such as candidate tyre, reference tyre, control tyre, braking force, braking force coefficient (BFC), dynamic tyre braking force coefficient and peak braking force coefficient are defined.
- Measurement approaches:
- Standard vehicle method - measuring braking‑related deceleration and calculating BFC.
- Trailer / tyre test vehicle method - real‑time measurement of vertical and longitudinal forces to derive dynamic and peak coefficients.
- Test environment and instrumentation:
- Track characteristics and macrotexture measurement requirements.
- Wetting and atmospheric condition controls to ensure repeatability.
- Precise instrumentation and data acquisition requirements for longitudinal and vertical force measurements.
- Tyre preparation:
- Tyre mounting, rim specifications, break‑in procedures, specified tyre load and inflation pressure for “loaded new tyres.”
- Data processing and validation:
- Calculation of braking force coefficients, adjusted reference tyre coefficients, and the relative wet grip index.
- Validation rules, result processing and example test report templates (Annex A).
- Control tyre concept: Use of control tyre sets when direct comparison on the same vehicle is not possible; storage, replacement and preservation rules.
Practical applications and users
ISO 15222:2025 is intended for:
- Tyre manufacturers conducting wet‑grip development and quality control.
- Independent test laboratories and homologation bodies performing performance verification.
- Vehicle manufacturers (OEMs) validating tyre choices for commercial fleets.
- Regulatory agencies and standards committees defining tyre performance labeling or procurement specifications.
- Fleet operators and procurement teams comparing wet‑braking performance for safety decisions.
Benefits include improved comparability of wet‑grip results, better repeatability across test facilities, and a clear basis for performance claims.
Related standards
- ISO 23671 - Passenger car tyres - Method for measuring relative wet grip performance (related methodology).
- ISO 4223-1, ISO 4209-1 - Terminology and tyre/rim specifications referenced.
- ASTM E965 - Pavement macrotexture measurement referenced for track characterisation.
Keywords: ISO 15222:2025, truck and bus tyres, wet grip, relative wet grip index, loaded new tyres, reference tyre, braking force coefficient, tyre test vehicle.