From the Muncie, IN Craigslist: Three wheel bike and Two wheel bikes
Am I missing something? Does "bi" not mean "two?" This seems to have become common usage.

Yeah, bicycle etymologically means "two wheels", but miniature etymologically means "make red", so what can you do.

And don't forget quad bikes!

I wonder if anyone will ever describe a unicycle as a "one-wheeled bike".

Good grief. There are thousands of Google hits.

And one in my home town!

And...more than 2 million on "3-wheeled bicycles."