"It's kind of an experiment," said Clifford Greer, 30, the lead organizer. "It's really a totally amazing thing, and unlike any other organized ride event."
Naked bike rides, he said, have proliferated around the world in recent years.
The first official Naked Bike Ride started in 2004 when a group of artists in Canada and a group of nude cyclists in Spain organized simultaneous naked rides. Since then, masses of naked riders have pedaled through 87 cities in the Americas, Europe, and Australia. This is the first event in Philadelphia.
The Naked Bike Ride has many aims, said Greer, an audio-visual technician.
Reducing wind resistance isn't one of them.
"Nudity is only a tool of the Naked Bike Ride," he said. "We want to put a spotlight on the vulnerability of cyclists, and put the safety of cyclists into the minds of drivers and other users of the roads."
Secondary goals, Greer said, include bringing attention to fuel consumption and spreading the message of a positive body image.
Karen Skorochod, 37, first heard about the Philadelphia ride on Facebook. She said she planned to drive down from Wind Gap, north of Allentown, to take part.
"I don't make a practice of being naked in public," Skorochod said. "But the part of this that really appeals to me is the body acceptance in all this. People come in all shapes and sizes, and I hope they all come out."
She said she was not concerned about strangers gawking at her as she pedals along the urban route.
"I don't know if it's the fact that I've had three children or not," she said. "But if you want to gawk, gawk. I am what I am."
Riders, who can participate anonymously, won't be required to let it all hang out unless they're comfortable with it, Greer said.
"We're asking people to go as bare as you dare," Greer said. "We want people to be comfortable and confident. If they ride in a bathing suit this year, they might ride in their underwear next year and naked the next."
Body paint will be available to those who want to ride without a stitch but still want a bare minimum of coverage.
City police, who learned of the event only Thursday, are taking a wait-and-see approach.
"If they're a friendly group who just wants to ride, it will probably be fine," said Lt. Frank Vanore, spokesman for the Philadelphia Police Department. "But if a criminal act is observed by police, they'll enforce whatever laws they need to."
Jeff Loyd, 32, said he'd be riding with a group of six from Community College of Philadelphia.
"I like riding my bike, and I like being naked, so it's a match made in heaven," said Loyd, who studies computer networking. "My only concern is the indecency laws. I really don't want to get arrested, though it probably would be funny to have that on my permanent record."
Alex Doty, executive director of the Bicycle Coalition of Greater Philadelphia, said the ride would definitely increase the visibility of city cyclists.
"I don't know what the reaction of bare flesh on a bicycle saddle is, however," said Doty, who won't be participating. "I'll be interested in hearing those reports."
Contact staff writer Sam Wood at 215-854-2796 or email@example.com.