Overview
ISO 4249-3:2010, "Motorcycle tyres and rims (code-designated series) - Part 3: Rims," defines the essential rim dimensions and contours required for correct tyre mounting and fitting. The standard focuses on the rim features that affect tyre compatibility and safety - such as rim contours, valve-hole details, bead seat geometry (cylindrical and tapered MT types), nominal diameters and circumferences, and permitted rim widths.
Key topics and technical requirements
- Rim contours and finish: Rims must be smoothly contoured and free of sharp edges to avoid tyre or valve damage.
- Rim valve hole: Specifies a standard valve-hole diameter of 8.3 mm, with rounded/chamfered tyre-side edges and burr-free hub-side edges. For snap-in tubeless valves the rim is counter-bored to reduce thickness to a maximum of 4 mm; an 11.3 mm hole is optionally permitted for some manufacturer requests.
- Bead seat types: Defines two primary bead-seat families:
- Cylindrical bead seat - contours, diameters and circumferences given in tables for code-designated rim sizes.
- Tapered bead seat (MT type) - 5° tapered contours, alternative well contours for wider rims, bead-seat contours for rims without humps (tube-type only), and hump circumference specifications.
- Rim diameters and hump circumference: Tables list specified rim diameters and measuring circumferences for both cylindrical and MT rims; Annex A gives a method for measuring MT rim circumference using an 8 mm ball tape.
- Designation and permitted widths: Rims are designated by nominal rim diameter code and nominal rim width (e.g., 18 × 1.85 or 17 M/C × MT 3.50). Permitted rim widths for each tyre section are provided (for example, tyre section 3.00 → permitted rim widths 1.60, 1.85, 2.15).
Practical applications and users
ISO 4249-3:2010 is used to ensure tyre–rim compatibility, interchangeability and safe mounting in the motorcycle industry. Typical users:
- Rim and wheel manufacturers (design and production tolerances)
- Tyre manufacturers (matching tyre bead profiles to rim contours)
- Motorcycle OEMs (wheel specification and procurement)
- Testing laboratories and quality assurance teams (dimensional checks and compliance)
- Service and repair workshops (correct rim/tyre pairing and valve fitment)
- Regulatory and standards professionals (type approval and certification)
Related standards
Keywords: ISO 4249-3:2010, motorcycle rims, rim dimensions, bead seat, MT rims, cylindrical bead seat, rim valve hole, hump circumference, permitted rim widths, tyre mounting.
