A MAN IN A BORAT UNITARD RIDES past me like some sort of gravity-defying, sexually perverted superhero, easily climbing the rocky Northern California incline up which I'm struggling to push my bike. I paw at my dusty water bottle and watch his bethonged ass shrinking in the distance. In about an hour he'll be named the 2008 Single Speed World Champion. All I want to do is survive.

What the hell am I doing here anyway? Well, it all started years ago, when my mountain bike's rear derailleur decided to disassemble itself during a ride. Naturally, this occurred when I was as far from the trailhead as possible and, shrewdly, had packed none of the tools I'd need in order to make the thing rideable again. Even if I had, the various pulleys and bolts had scattered themselves along the trail like so much gorp. So as I hiked through the woods, back to the relative civilization of suburban New Jersey, walking my bike up climbs and then coasting down, I resolved to convert it to a single-speed.

A single-speed, if you don't already know, is a bike with a single gear ratio: one chainring up front, one cog in back. Like a BMX. No shifters or derailleurs to fail on you, no granny gear to bail you out, and nothing to think about while you're riding except riding. Instead of hunting for the right gear on hills, you attack them at speed so your momentum carries you to the top, and on all but the steepest and most technical climbs you get up there faster and more effectively. Basically, single-speeding is both totalitarian and meritocratic, in that it offers you neither choices nor a safety net.

Over the years, the single-speed "movement" has attracted a large number of mountain-biking devotees, whose intricate facial-hair patterns and tattoos counterbalance the simplicity of their bicycles and whose disdain for things like officially sanctioned races, spandex, and sobriety runs as deep as their aversion to gears.

It's in this spirit that the Single Speed World Championships were born, best anyone can guess, in 1995. Despite the name, the SSWC is sanctioned by no organization except for a consensus of dedicated single-speeders, and every year it bounces from international locale to international locale like the fugitive from decency and legitimacy that it is. This time around, it's in Napa, at Skyline Wilderness Park.

When you win the SSWC, you don't get a jersey, a trophy, or cash. You get a tattoo. It's mandatory; you pick the spot. And while the SSWC is a party, it's also very hard and, believe it or not, highly competitive. The 2007 winner was national cross-country-mountain-biking champ Adam Craig, who's in Beijing competing in the Olympics while we're here in Napa. It's tempting to think a race like this isn't as difficult as a "real" race, but the fact is it's even more difficult. An epic-length mountain-bike contest is going to hurt, even if, like some kind of Lycra-clad Mormon, you've been watching your diet, going to bed early, and tapering according to Chris Carmichael's instructions in Bicycling magazine. But doing one hungover and ill-prepared, as SSWC custom dictates, is absolutely excruciating.

Especially when there's nothing between you and your torturous race saddle but a pair of cotton briefs. Ridiculous costumes are an SSWC tradition. Accoutrements like frilly dresses, neon unitards, Helga wigs, fishnets, feather boas, and faux fur almost outnumber traditional cycling kits—and that's just on the men.