I get enough emails asking about bike rentals that it makes sense to post this to save everyone some time.  I do not offer bike rentals.  As a one-man operation, I don’t have time or space to provide a top-notch rental service.  There are several shops in Marin County who do offer rentals of various style of bikes.  Your best bet is to google search “marin county bike rentals” and contact the ones who seem to have what you’re looking for – road bikes or mountain bikes.