Originally Posted by
Commando303
What's "650b"? All I've come across are 26" ad 700c, the latter of which I understand to be "29"." Most of the so-called "commuter-bikes" I've encountered have been shown to come with "700X35" wheels, which, I believe, means they're twenty-nine inches by 1.5 inches, as opposed to the few I've seen in 26", which, too, are said to be 1.5 inches wide.
650b(584mm) tires are fairly uncommon. They're about midway between the size of 700c(622mm) and 26"(559mm).
They are being used by a few bike makers who believe 700c doesn't work well for smaller frames/riders. If your bike store doesn't carry them (some don't) you'd probably have to find them on-line.