MELBOURNE'S $5.5 million bike share scheme isn't attracting many users, and Mike Rubbo reckons he knows why: the helmets.

Fewer than 70 trips are being made a day on Melbourne's 600-bike system, a tiny number of journeys compared with the take-up rate seen in bigger schemes introduced in 135 cities around the world.

Mr Rubbo, a Sydney filmmaker and bicycle blogger, will try to underscore his argument on Saturday morning by leading a protest ride from Melbourne University without a helmet, risking a fine of $146. He wants Roads Minister Tim Pallas to follow Mexico City's lead and waive compulsory helmet laws for the bike-share scheme.

Melbourne is the only city in the world to have introduced a bike-share scheme and retain its compulsory helmet laws.