neptronix wrote:erm, isn't it at 700c wheel with a 2in. tire on it?
That is what many bicycle shops have told me.
Bicycle wheel sizes are based off the total diameter of the expected tire plus the rim itself.
So for example, a 20" wheel in bike terms is a 16" wheel in motorcycle terms, because there is usually a gigantic tire on the thing.
Technically the rim is 622mm by whatever the INSIDE rim width is (typically 18-20mm). "29er" is a marketing term, not necessarily reality, but that said, my 622 rim, plus a 2.0" (50mm Schwalbe) tire is very close to 29" in diameter. Here's an article about it:
(29er on left, 26" on right)