I hadn't really thought about it, but a friend of mine recently got a Bacchetta recumbent that's 700-size, but she mentioned a lot of the older Bachettas were 650- they were just now going to 700s across the line. The significance around here is that most of the 650's you'd see here aren't on upright bikes. Which also means tire availability should be a little better than you'd imagine.
Similarly, I saw a kid-size racing bike the other day, and it's hard to imagine that thing would be in production if the wheel size wasn't being used on some recumbent somewhere. Or maybe it's the mini-velo fad, but either way, it gets some odd sizes in production.
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"be careful this rando stuff is addictive and dan's the 'pusher'."