There’s one key difference between “Race Across the Sky,” last year’s documentary on the Leadville 100, an epic mountain bike race two miles above sea level, and the just-released “Ride the Divide,” which chronicles a lesser-known, 2,700-mile race that follows the Continental Divide from Banff, Alberta, Canada, south to the Mexican border. I’ll get to that difference in a sec.

“Ride the Divide” follows the 2008 race of the same name. It had one of its first showings nationwide Thursday at Carrboro’s Century Center, in part because the film features the race’s winner (who also is its organizer), Chapel Hill’s Matthew Lee. Lee, pictured above, is well-known in Triangle mountain biking circles, in part because of his prowess in the saddle, in part because of his advocacy for local trails. But I’m guessing that even those who thought they knew Lee before seeing “Ride the Divide” learned a thing or two about  him. Thanks to the film, they also learned a thing or two about this obscure race that began, essentially, in 1999. Of Ride the Divide, which is mostly on gravel roads and trails, Outside magazine wrote: “The toughest bike race in the world isn’t in France.”

You get a sense of that early on. On Day One, one racer covers 110 miles of mostly gravel forest roads and logs 8,000 feet of climbing (there’s more than 200,000 feet of climbing overall). “I can’t believe I’m going to do this every day for the next three weeks,” he says outside a convenience store as daylight fades. A day later, the riders encounter a three-mile stretch of trail that’s snowed in; one particularly tricky passage involves traversing a 45-degree slope. And a day after that, two riders have a pair of encounters with grizzly bears. There’s some walking, some hike-a-biking, and lots and lots of riding — more than 100 miles a day for those who hope to finish within a month. And the riders do it all on their.

“There’s no support team,” says racer Mike Dion, who is also the film’s executive producer. “It’s entirely self-supported.”

Some of the film’s more entertaining moments are when it captures these episodes of self-sufficiency. One morning, Dion paws through a baggie of assorted pills. “I’m not really sure what all these are,” he says, “but I’ll take them.” Another racer, eager to hit the road early one morning, has a quick breakfast of coffee grounds sprinkled over a convenience store cherry pie.

The racer’s reliance on roadside convenience stores for much of their nutrition is especially vexing for Dion, a vegan. “I’m determined to find something that’s not processed,” he says while roaming the bright florescent aisles of one store. He emerges with a jar of pimento-stuffed green olives.

There are injuries, from a litany of blisters to Mary Metcalf-Collier’s legs, “swollen up like sausages. I think there’s blood pooling up underneath,” she says in a quick self-diagnosis.

At one point, Dion examines his feet. “This toe is numb,” he says, wiggling his middle piggy. “Has been for five days.” The film’s associate producer, Anthony Cimino, looks on. “What do you need that toe for?” he wants to know. Dion’s ensuing glare is classic.

And the film captures that moment that all of the racers fear. When Dion decides his body has had enough he pulls to the side of a desolate dirt road and calls home to tell his family he’s done. “We love you daddy,” his daughter replies. A lot of guys at the screening avoided eye contact with one another after that exchange.

The racers meet a variety of characters along the way, from a biker (motorized) who’s on his way to the Arctic Ocean, to a bearded Ernest T. Bass type who explains the role his dog plays in his remote logging operation. “I tell him, ‘You bark, and once you hear the click-click’ ” — here he pretends to hold a shotgun in the air — your job is done.”

The film doesn’t catch up with Lee until near the end, in part because Lee, who has won the race four times, is so far in front of the other riders. When the camera crew does catch him, in Colorado, he hardly looks like a guy who has been riding a mountain bike 140 to 160 miles a day for the past two weeks. While others deal with psychological demons and failing bodies, Lee’s biggest challenge seems to be finding the right granola bars. Perhaps he seems that way because he knows that the real challenge of his life awaits back in Chapel Hill: a week after he crosses the finish, his wife, Katie, will give birth to their first child.

As he enters New Mexico, Lee acknowledges as much. Sitting on the porch of a modest, white clapboard church, he reflects, “Maybe I’m passively mellowing as I near the end. When I get back, my life will be more intense. I’m not prepared for that. Certainly, my life will change in ways I can’t predict.” A couple days latter, in the dark of night, there’s one person to congratulate Lee as he crosses the Mexican border. It’s a far cry from cruising down the Champs-Élysées to the cheers of hundreds of thousands of fans.

So, the key difference between “Race Across the Sky” and “Ride the Divide”? When “Race Across the Sky” aired in Raleigh last year, mountain bikers could be heard leaving the theater making plans to be part of the next Leadville 100. At the conclusion of “Ride the Divide” Thursday night, Lee, who was on hand for a Q&A, asked if there were any takers for the race. There was nervous laughter until someone in the back yelled out and confirmed there was only one person in the room crazy enough to race a mountain bike the length of the Continental Divide.

“You!”

“Ride the Divide” is expected to play in local theaters in August.

Come back tomorrow to GetGoingNC.com for highlights from Matthew Lee’s post-screening Q&A.