Overview
ISO 5775-2:2021 - Bicycle tyres and rims (Part 2: Rims) specifies the geometrical dimensions, profiles and designation/marking rules for bicycle rims used with corresponding tyres. The standard covers straight-side (SS, TSS), hooked bead (HB) and crotchet (C, TC) rim types and provides requirements relevant to tyre fitting, rim profile, rim diameters, valve hole placement and rim base protection. It is part of the ISO 5775 series (ISO 5775‑1 covers tyre designations).
Key topics and technical requirements
- Rim types and profiles: Defines profiles and tolerances for straight-side, tubeless straight-side, hooked bead and crotchet (including tubeless) rims, with figures and tables for dimensioning.
- Rim diameters and measured bead seat: Provides nominal diameter codes and measured rim diameters (with measurement tolerances) used to ensure tyre/rim compatibility.
- Designation and marking: Specifies how rims must be marked and designated (examples in the standard: 400 × 20SS (ISO 5775-2), 622 × 25TSS, HB 422 × 25 (ISO 5775-2)).
- General requirements:
- Smooth rim contour and chamfered or rounded edges to avoid tyre damage.
- Valve hole placement to permit inner-tube use and safe tyre installation/removal.
- Rim base protection requirements for rims with through‑drilled spoke holes (including airtight sealing needs for tubeless applications).
- All dimensions refer to a built wheel with rim base protection in place.
- Symbols, definitions and measurement methods: Includes standardized terms (rim base, tyre side/weather side) and symbols; Annex A gives methods for measuring and gauging rim dimensions and was updated to simplify redundancies and add precision for modern measuring tools.
- Tubeless provisions: New clauses cover tubeless straight-side and tubeless crotchet rims and specify rim profiles and measured diameters for tubeless-ready applications.
Applications and who uses this standard
ISO 5775-2:2021 is used to ensure safe, interoperable and consistent bicycle rim design and tyre fitting. Typical users include:
- Rim and wheel manufacturers (design, production tolerances, tubeless sealing)
- Bicycle designers and OEMs (component compatibility and specification)
- Wheel builders and assembly shops (correct rim/tyre matching, marking verification)
- Test labs and conformity assessors (dimensional checks, tolerance verification)
- Procurement and quality teams (product specification, supplier compliance)
- Aftermarket and tubeless conversion kit providers (seal design, valve placement)
Related standards
- ISO 5775-1 - Bicycle tyres (designation and dimensions) - directly complements ISO 5775-2 by defining tyre sizing and labelling used with the rims specified here.
- The ISO 5775 series provides the authoritative framework for tyre and rim compatibility.
Keywords: ISO 5775-2:2021, bicycle rims, rim dimensions, tubeless rims, hooked bead, crotchet rim, straight-side rim, rim profile, rim marking, rim base protection, measured rim diameter.
