For hard-core biking, try one gear, no brakes

Jack Curry's bicycle is missing a few pieces, but he likes it that way.

It's a gorgeous vintage Poglioghi, matte gray, outfitted with handcrafted parts imported from Italy and painstakingly pieced together by Mr. Curry himself. The cost: a whopping $1,500.

But he saved money by leaving out a few key components. Like brakes - there aren't any. And gears - there's just one. And there's no free wheel, either, so he can't coast - as long as the bike is moving, he has to keep pedaling.

"It's chopped down, super sleek, and fast," says Curry, a junior at Colby College in Maine, who's been riding it every day since July.

Curry's bike is one of a fleet of practically weightless, difficult to stop, extremely speedy rolling bullets that make up the newest trend in the two-wheeled world: highly specialized velodrome sprint bicycles being ridden on city streets. Designed for Olympic-style banked oval racing, they're called "track" or "fixed-gear" bikes, and almost overnight they've rolled out of their niche and into America's rush-hour traffic, generally ridden by people who have far more tattoos than you.

"These things are a lawsuit just waiting to happen," says Sky Yaeger, vice president of product development and marketing at bicyclemaker Bianchi USA, in Hayward, Calif. "But, you know, there's just nothing more beautiful than a fixed-gear bike."

She should know: she designed the Bianchi Pista, a $550 eye-catching, all-chrome track bike that has played a big role in bringing fixed-gear into the mainstream. Although Bianchi had been selling entry-level track bikes for several years (competition-quality ones can cost thousands), the first chrome model, in 2004, sold like gangbusters. Bianchi is expected to roll out its third chrome Pista at a trade show in Las Vegas next weekend.

Now more than a dozen bicycle manufacturers are making track bikes for the general public. The industry is close-lipped about sales figures, but insiders estimate that close to 10,000 track bikes will be sold this year - a tiny fraction of the 18 million total bicycles sold in the US every year. But, they say, the segment is rapidly growing - sales have tripled in the past few years, according to industry observers.

"Three years ago, there were almost no new track bikes. Now it seems like everyone in the world is making one," says Brad Baker, co-owner of New York's Trackstar NYC, the first shop in the country completely devoted to fixed-gear bicycles. His store, which opened in June last year, carries both restored vintage racing frames and shiny new bikes by Bianchi, Fuji, Surly, and Soma. Prices start at around $400 and can break two grand for a top-of-the-line Italian model.

Riders swear by the bare-bones feel of a "fixie," which, thanks to its pared-down drivetrain (think of a unicycle with two wheels) is extremely responsive and efficient. Fitness buffs argue that because there's no coasting, track bikes make for a great workout. And thanks to their simplicity, there's practically nothing to break - or steal. That minimalism has made them a favorite with messengers, who have been using them for years (see Kevin Bacon's 1986 courier classic, "Quicksilver"). Indeed, some say, it's the messengers and their gritty image that turned civilians on to track bikes. "A track bike reeks of messenger heaven," says Dmitri Laddis, a New York pediatrician who dropped $800 on a fixed-gear bike this spring.

Critics, however, say that track bikes are just a fad that, considering the risks and difficulty of using them, will soon disappear.

"It's very hard to stop. It's hard on the knees. It's tiring. I tried riding on bike paths and I almost killed a woman," says John P. Smith of Alameda, Calif. The experienced road rider bought a fixie in the spring. Now he's selling it. "I only rode it 24 miles," he laments. "This trend won't last."

Then there's the legal element. Most cities require bikes to have brakes, and even though experienced fixie fanatics swear they can stop on a dime - braking occurs by pedaling slower and applying back pressure on the pedals - reports of police handing out tickets are growing.

Still, for the most hard-core fixed-gear faithful, it's an addiction. Less than four months after mounting a track bike for the first time, college student Curry sold his two conventional, geared bikes; bought a second track bike; and is eyeing a third. And he's converted two friends. "Fixed-gear riding is spreading," he says.