Quote Originally Posted by zia View Post
OK -- I've found tubes that will work. As for the tire: if I currently have a 26 x 7/8 (aka 22.2 mm), would 26 x 23 work? I'm not finding any 26 x 22.
The 23s will be fine; most rims take a range of tyre widths, within limits, and you can sometimes find those limits on the rim manufacturer's website. You might find they will take something like 20mm width to 25mm width. I have 650s and I'd happily use that sort of range without even checking, but most 650c roadie tyres will be 23mm, or slightly narrower for some tri tyres.

Just check that you're getting 650c tyres (ETRTO size 571mm) for a 650c rim rather than 26in (ETRTO size of 559mm, which is the garden variety mtb size).

And a huge +1 for Sheldon on tyre sizing.