DAY 25, JULY 9, 16:46:23 MDT: Hey, Tom, it's Jon Billman, Silver City. The folks at Gila Bike and Hike are amazing. Came in on spit and prayers with these tires.... They got me some new skins and some new slime tubes and I'm ready to tackle the last section here.... Camp in the Separ area and then head for the border in the morning. All right, bye.

The evening Chihuahuan Desert is magical. The yucca and ocotillo mark horizontal depth, and a monsoon lightning storm plays the sky as I climb for the Divide, crossing it for the 28th time. I haven't developed any sort of powers that resemble a sprint, but I find that by now I can draw from what Matthew Lee calls "inner diesel power." In the last of the twilight, I experience the sensation mountain bikers call flow. My new tires are the perfect tread pattern for the desert. The bike courses over the trail like water through an arroyo after a desert rain. The weather front cools my skin. The water in my CamelBak tastes like fine beer.

The desert is my favorite place to ride. But in full darkness it's the trickiest, because even with the best lights, sand looks flat and even. I lay the bike down three times at 15 miles per hour before I throw my sleeping bag on the sand, crawl in, and close my eyes. It isn't five minutes before the biting ants snuggle in.

I break camp at 3 a.m. Earlier I dropped a Fig Newton and now I watch with my headlamp as a scorpion carries it away—where did he sleep? It's a real time trial now. I could dump my gear, but I want to make the Mexican border in the same way I left the Canadian one—self-supported and overloaded for bear. I'm not gonna be fast, but I can be complete.

Hours pass. I've hit pavement, and the chevroned tires buzz as I stand on the pedals, determined to redline it. The sun is nearing its apex. I have not yet considered that it could be late morning, but, dammit, the sun looks straight overhead. Well, I figure, if I make the cutoff, great. If not, I'll have all winter to bang my head against one wall and drive Hilary up the other.

My lungs are smoked when I hit the green sign with a cartoon pronghorn marking Antelope Wells. I fall off the bike and hobble into U.S. Customs. The air-conditioning is a revelation.

"Did I make it?"

Make what?

"Is it really 11:25? a.m.?" Maybe they haven't adjusted for daylight savings. A customs officer with a gray government-issue mustache checks his watch and nods. Half an hour to spare. Agent Tim Balderston hands me a spoon and a container of astronaut ice cream, the kind that looks like frozen caviar. "Here's your G-D celebration ice cream."

I finish tenth, 35 minutes shy of 25 days. It will take three months for all the feeling to come back to my hand—my body let me finish, but it's gonna punish me for it later. Nathan Bay finishes but misses the cutoff time by a few hours. Jeff Kerby's race ended at the Española hospital. He tells me he left the puke-filled Wal-Mart tent up in the forest, violating every brand of backcountry etiquette. "Some emo kids might want to visit it," he says. "Be close to death."

Both Matthew Lee and Nathan Bay will be back on the line in Roosville in 2008—they're addicted and have unfinished business to tend to. As for Jay Petervary, the GDR winner is back in Jackson Hole, busy as a one-armed drywall hanger, which he sort of is if you consider his numbed left hand. Nah, he tells me—until someone breaks his record, there's no need to tempt the GDR again anytime soon.

But the race dopes your blood, and life off the Divide can seem so banal, so comfortable. "My wife and I have talked about it," Jay says. "We might do it on a tandem."