日本工業規格
ISO 5775 is an international standard for labeling the size of bicycle tires and rims. The system used was originally developed by the European Tyre and Rim Technical Organisation (ETRTO). It is designed to make tire sizing consistent and clear. It replaces overlapping informal systems that ambiguously distinguished between sizes. For example, at least 6 different "26 inch" sizes exist (just by American notation), and "27 inch" wheels have a larger diameter than American "28 inch" (French "700C") wheels. The Japanese Industrial Standards Committee also cooperates with ISO 5775. The corresponding Japanese standards are JIS D 9112 for tires and JIS D 9421 for rims.