In Reply to: Re: motorcycle tire on 8N posted by Gaspump on July 23, 2018 at 13:38:21:
Metric tire section size designations on inch rims was an industry initiative not a government mandate. Started in the mid 70's with passenger car tires and has expanded from there.
A small number of European manufacturers (e.g. BMW, Ferrari) experimented briefly with metric rim diameters but that never caught on. Tires for those old wheels are exceedingly hard to come by.