uuuuuggghhh i am realizing that the euros (michelin, schwalbe, etc) like marking their tires as 650x25A, where:
- “650” is the historical-french-approximate-outer-diameter-in-mm
- “25” is the actual tire width in mm (never mind that a 650A would historically be a ~35-37mm tire, so a 650A-sized, 25mm wide tire will be noticeably less than 650mm in diameter)
- and “A” indicating that it fits on a 650A-sized rim, AKA 590mm bead seat diameter
If the letter at the end is supposed to be part of the rim size indication (rather than a historical curiosity from the 1970s indicating the need for a hooked rim), then “650x47C” - like everyone sells nowadays - implies that it’s for a 650C/571mm BSD rim, not a 650B/584mm BSD rim. This is clearly not the case, and yet…
TL;DR everything sucks, even the tire makers don’t understand why they put the markings on the sides of their tires, we should all use ETRTO like St. Sheldon evangelized.