Ever come across a gang of rowdy bicyclists clogging the streets of Downtown Berkeley, accompanied by an unholy racket blasting from a portable sound system? Out-of-towners may wonder what the hell is going on, but locals have no excuse not to know: It’s Berkeley Critical Mass, a “global nonauthoritarian movement of celebration, street reclamation, and demonstration,” as described by BerkeleyCriticalMass.org. Riders gather every second Friday of the month at the Downtown Berkeley BART station for a 6 p.m. ride that forsakes bike lanes for total takeover of the streets — and often jam up intersections through multiple light cycles along thoroughfares like Shattuck Avenue, Telegraph Avenue, and Dwight Way. Still going strong after fourteen years, Berkeley Critical Mass is a spectacle as much as a statement, not least because of the huge speaker, often pulled on a trailer behind a bike, that blares classic and indie rock while announcing the group’s presence well before and after it comes into view. “Critical Mass is a rolling free-speech stage and playground,” the Web site declares, and what good is free speech without a soundtrack? To keep rolling for this long, protest has gotta be fun.