The Biker Who Took Big Air to the Big Time

If you associate “Jackass” with outrageous, over-the-top feats, know that the guys behind that hit MTV stunt show appreciate athleticism, too. In his new documentary “The Birth of Big Air,” Jeff Tremaine, the “Jackass” co-creator and director, pays tribute to Mat Hoffman, the freestyle BMX biker who ushered the sport from backyard ramps in the 1980s to the two-story-tall half-pipes of the modern-day X Games. The eerily mature film is also a grown-up endeavor for the “Jackass” star Johnny Knoxville, who is one of its producers.

“The Birth of Big Air” made its debut at the Tribeca Film Festival on Saturday, and will also be shown on ESPN as part of its “30 For 30″ documentary series. At the festival, Mr. Hoffman, Mr. Tremaine and Mr. Knoxville spoke with ArtsBeat about the film and their friendship, and shared some of the gory, possibly illicit tales of Mr. Hoffman they couldn’t get into the movies. These are excerpts from that conversation.