rhm

As for the Trek 720, the '82 being a unique beast designed for 700c wheels anyway (they went to 27" in '83 ff), I don't see it as a great 650b candidate. You can do it, of course, but I don't see much benefit.

As for touring with 650b, as has been stated, you can do it. You can carry a spare tire anyway, and probably should. Depending how far you're going, and how much time you have for your tour, there may or may not be a down side to 650b. Most likely, wherever you are, you can call a bike shop and have them FedEx a tire to you while you wait a day or two. If you're out on a week long tour, that may not be an option; but if you're out on a leisurely cross country trek and a day or two delay doesn't bother you, then what the heck.

On my last tour, a comparatively new 650b tire blew out for no apparent reason. I had a spare; no problem. Had I needed to get a replacement 650x38b tire, even in Saratoga Springs NY, it would have been a major hassle that I didn't have time for. 700c would have been easy.

adventurepdx

Hmm, interesting. I didn't know about that. Do you remember which bikes they were?

I had a mid 80's Schwinn Collegiate three speed, which was a Taiwanese model (probably made by Giant.) And to my frustration, it used the 597 size wheel/tire.

djb

all this weird rim size touches on the whole 700x38"B" 635mm rim size (vs 700 "C" 622mm rim size)-- "B" are postal bikes in some countries and some older bikes too----don't make this mistake ("B" vs "C")