If you think vice versa then please tell me why and which of the 39 Melanoma is being broken by biking on Shabbos
Which of the 39 melachos is muktzeh? Which of the 39 melachos is carrying in a place where the eruv is down? Which of the 39 melachos is using an umbrella?
The answer to all of these is none, but there are things which are assur on Shabbos which are not one of the 39 melachos.
I was under the impression that it was well known that riding a bike on Shabbos has been accepted as assur, whether because of uvdin d’chol or a gezeirah, as Mammele said.
I guess I was wrong, and some people really don’t know.
http://hebrewbooks.org/pdfpager.aspx?req=19979&st=&pgnum=290&hilite=