Overview
ISO 5751-2:2010 - "Motorcycle tyres and rims (metric series) - Part 2: Tyre dimensions and load-carrying capacities" - is an international standard that specifies tyre size designation, dimensional data and standardized load-carrying capacities for metric-series motorcycle tyres. It applies to tyres with a height-to-width ratio of 100% and below and provides the technical basis vehicle and tyre manufacturers, testing laboratories and regulators use to ensure compatibility and safe operation.
Key topics and technical requirements
- Tyre designation and marking
- Specifies the tyre size format including service description (load index and speed symbol). Example marking formats:
100/90 – 18 M/C 56 P (diagonal), 100/90 R 18M/C 56 P (radial).
- Tyre dimensions
- Tabulated design and in‑service dimensions (section width, overall diameter) for multiple size series. Tables 1–14 list design and maximum in‑service widths/diameters for different tread configurations.
- Measuring procedure
- Defines mounting and inflation procedures for measurement (measuring rims per ISO 5751-3), required inflation pressures for normal/extra/light-load tyres, and a 24 h conditioning period prior to taking measurements. Example inflation guidelines include 225 kPa, 280 kPa, 330 kPa depending on load and speed symbol.
- Tread configurations
- Classification of tread types (A–D) with common service attributions (highway, off‑road, mixed).
- Load ratings and load indices
- Tables 15–29 provide standardized maximum load‑carrying capacities per tyre size; Annex A contains harmonized load indices. Provisions allow adjustment of load capacities at reduced speeds (see Table 30).
- Inflation pressure guidance
- Recommended inflation pressures tied to rim diameter codes, tyre versions (light/normal/extra‑load) and speed symbols. These are guideline values to be agreed between tyre and vehicle manufacturers.
Applications and who uses it
- Tyre manufacturers - design, mark and certify metric-series motorcycle tyres for consistent dimensions, load ratings and compatibility with approved rims.
- Motorcycle and vehicle manufacturers - select tyres and specify clearances, load capacities and inflation recommendations during vehicle design.
- Test laboratories and certification bodies - verify tyre dimensions, perform load/pressure testing and confirm compliance with ISO requirements.
- Regulatory agencies and fleet operators - reference for safety, type-approval and maintenance guidance in procurement and inspection.
- Aftermarket retailers and mechanics - use dimensions, load indices and inflation guidance to recommend correct tyre fitment and pressures.
Related standards
- ISO 5751-1 - Motorcycle tyres and rims (metric series) - Part 1: Design guides
- ISO 5751-3 - Part 3: Range of approved rim contours (measuring rims)
- ISO 4223-1 - Definitions of tyre industry terms
ISO 5751-2:2010 is essential for ensuring safe, interoperable tyre and rim combinations in the metric motorcycle tyre sector and supports consistent specification of tyre dimensions, load‑carrying capacity and measurement practice.
Open preview (PDF)Motorcycle tyres and rims (metric series) — Part 2: Tyre dimensions and load-carrying capacities