(BIKERS UNITE) The last Friday of every month, bikers meet at Westlake Center for a big ride through the city. What's special about this Friday is that it's the first Critical Mass ride since two CM riders, Zack Treisman and Jace Brien, were roughed up by undercover King County Sheriff's detectives in an apparent fit of "law enforcement." (Westlake Center, Fourth Ave and Pine St, www.seattlecriticalmass.org. 5:30 pm, free.)