Bicyclists will take it all off - well, maybe half off - on a Shanghai ride for World Car-Free Day. They want to call attention to healthy living.

Bicyclist and environmentalist Zhang Linyuan plans to strip down to swimming trunks and shoes and lead a "clothing optional" ride in Shanghai on Saturday to promote biking for the World Car-Free Day.

The variously called "the naked, half-naked and clothing-optional" ride will take place after a fully clothed event in which 37-year-old Zhang leads bicyclists on an official ride to mark the day and the importance of reducing the number of polluting cars.

The World Car-Free Day officially falls next Thursday, but activities to convey the message will take place in Shanghai this weekend.

The stripped-down bike route has not been announced and interested people will just have to tag along after the official bike ride and see what unfolds.

Zhang, founder of Prodigy Mountain Bike Club that organizes this biking event, suggests they gather at 11am on Longteng Ave, dubbed as "Shanghai's Little Bund," in Xuhui District.

"Of course, we will not hide ourselves in the dark. Instead, we will take to busy roads because after all, the event is to promote biking and a low-carbon and eco-lifestyle," Zhang tells Shanghai Daily.

Speaking of the absence of shirt and trousers, he says, "It doesn't involve anything bad at all, as you can see from our photos taken on last year's ride, which was healthy and sunny." Girls wore bikinis.