DAY 2, JUNE 16, 2007, 13:24:14 MDT: This is Dave Nice in Columbia Falls.... Good, feel good. Got chased by a bull moose for about a quarter-mile.... Yep, it's all good. Weather's nice, and moving a lot faster than I was last year. So it's all good. Talk to you later.

It's hard to argue that the GDR is not the toughest bike race in the world. Imagine a Tour de France run on the honor system, with no checkpoints, no officials, no drug testing. Now sprinkle the course with grizzly bears, goathead thorns, mosquitoes, and rattlesnakes, not to mention almost 200,000 feet of climbing over fire roads, dirt lanes, singletrack, and a smattering of pavement. "You ride your bike from Canada to Mexico," Curiak says, "you've got integrity."

The rules are simple: Don't take any prearranged support. Stick to the course, accept no lifts, and leave the midway point, Steamboat Springs, Colorado, by noon on Day 12. Cell phones are for emergency use only, in which case you'll be well out of range and can use them to reflect sunlight in Morse code at commercial jets. Get your front wheel to the border by noon on Day 25. That's about it.

The Divide has seen riders before: Solo cyclist Frank Lenz traversed it on his wooden-rimmed Victor in 1892, and five years after that, black buffalo soldiers from the 25th Infantry pedaled their 80-pound loaded Spalding "safety" bicycles 1,900 miles from Fort Missoula, Montana, to St. Louis in a blistering 40 days. But the official Great Divide Mountain Bike Route wasn't mapped until the 1990s, by Michael McCoy, author of Cycling the Great Divide: From Canada to Mexico on America's Premier Long-Distance Mountain Bike Route. In 1999, using the somewhat crude maps produced by the Adventure Cycling Association, endurance legend John Stamstad time-trialed the route, arriving in Antelope Wells in a mere 18 days, 5 hours, and 37 seconds.

The first actual Great Divide Race took place in 2004, when Curiak and Basinger battled for the win and it took even Matthew Lee a month to make Mexico. That year there were seven riders and four finishers. The next year, four made it again, including the GDR's only female finisher to date, Trish Stevenson, and the first single-speeder, Kent Peterson. By then, this turtlesque thriller was attracting fans on the Web, an online fan base few had any idea would metastasize the way it has. Pedalphiles from all over follow the updates: Riders check in from pay phones, using an 800 number to leave a message for logistics man Tom Purvis, 44, who works at Absolute Bikes, in Salida, Colorado, one of only a few shops near the route that can give racers the cyclopedic NASCAR treatment. Purvis is the wizard behind the GDR curtain, transcribing the voice mails and posting them online. Fans can also tune in to MTBCast.com to hear Joe "Polk and Beans" Polk summarize the day's events in his Georgia drawl: "MTBCast is on the air!"

A couple of years ago, while Googling the Tour de France, I became part of the GDR's online congregation. Coffee cup in hand, I quickly grew addicted to the race's hardcore brand of velopornography. I was spellbound. A recreational mountain biker at best, I pictured myself out there in a way I don't when watching a Giants game or the Tour.

The dispatches were nightmarish. In 2006 there was extreme puking, saddle sores, a stolen bicycle, bad hygiene, and swollen feet. I began living vicariously through the only two racers still competing—Matthew Lee, days ahead and waiting out a deluge underneath an abandoned bus in Colorado, and the mysterious Kenny Maldonado, a New Yorker drudging through Wyoming's parched and windy Great Divide Basin, disappearing from the race's radar for four days, leaving his fan base to fear he'd shat the bed in the purple sage. But even two weeks behind, Maldonado would have been the winner had something happened to Lee. What mattered to me was that they were out there, riding deep into fat-tire mythology—Make it me! I sang to my wife.

"What's the big deal—you're gonna have all day with nothing to do but ride your bike," Hilary said. She was right, of course; riding my bike had become my sole task on the planet. But that encompassed so much. I was hell-bent on seeing for myself whether the GDR was indeed the next last great American race. I wanted a genuine-article western. I did not want to ride in circles in a 24-hour race, endurance cycling's tour d'hamster. I wanted a journey. In the GDR, a bike is more than a toy; it's your vessel.

I collected panniers, a microtent, a light system for night riding, the Adventure Cycling Association's route maps, and a sleeping bag that weighed less than a diaper. I ducked into AutoZone for a shiny foil windshield sunshade—the de facto sleeping pad of the GDR. "You go ahead and get this race out of your system," Hilary told me. "But I don't want to get a call from Butte saying your butt's bleeding."