Dave Byers rides with his dog Kenai along a Jackson, Wyo., trail with the Tetons in the background.

Above, Kathy Evingson tries to ride her bike through the deep snow during the Little-Su 50K at Point Mackenzie near Knik, Alaska. The 31-mile trek across frozen rivers and snowy swamps - open to skiers, snowshoers and runners - is often won by competitors using bicycles.

Greg Matyas, owner of Speedway Cycles bicycle shop in Anchorage, Alaska, works on a fat-tired snow bike for the Iditarod Trail Invitational bike race.

Knik, Alaska ? Adventure racer Michel Villon was pushing his bike through deep snow on a frozen lake when a team of sled dogs swished past.

“I’ll trade you,” Villon yelled to the musher, who shook his head and smiled as the dogs whisked him away.

Villon was competing in the Little Su, a 31-mile trek across frozen rivers and snowy swamps. Open to skiers, snowshoers and runners, the February race is often won by competitors using an unlikely mode of snow travel – the bicycle.

Though classic sports of winter still rule, especially in soft snow, the number of snow bike devotees has grown steadily since fat-tire bikes came on the market three years ago.

The extra-wide treads allow riders to navigate snowy trails that stymie even the burliest mountain bikes. And biking routinely trumps skate skiing, the fastest cross-country ski technique.

“We’ve never really expected it to be a huge thing,” said Peter Redin, general manger of Minneapolis-based company Surly Bikes. “It’s a very small demographic who wants to go do extreme types of races, or get to places they couldn’t access on a different type of bicycle.”

Mountain bikes work fine on packed trails, but in soft snow the skinny tires get stuck and spin out. Even studded tires, designed to bite into ice, are useless on powdery, ungroomed trails.

Options abound

Surly makes the most affordable and popular snow bike, the Pugsley, which first hit bike shops in 2005. The company sells more than 300 each year, Redin said.

Several craftsmen in Alaska and other states make small batches of higher-end snow bikes, geared toward more serious riders, that can cost more than $3,000.

“The bottom line is that there are way more options for a quality snow bike than there were two years ago,” said Dave Byers of Driggs, Idaho. Byers traveled to Alaska in February to compete in the Susitna 100, a two-day companion race to the Little Su.

In both races, nearly all the cyclists used chubby tires for extra traction and flotation on the new, wind-whipped snow. Like when driving a car in sand, riders partially deflated their tires to improve traction in the soft trail conditions.

“Since the rims are twice as wide, you can use wider tires,” said Brij Pontis, an Anchorage endurance biker who finished second in the Little Su cycling division. “When you let the air out, you get a bigger footprint on the snow, which allows you to float.”

Walk, don’t ride

But even fat tires have their limits. Many bikers quit after discovering that recent heavy snows had rendered much of the trail unrideable.

Others, including Villon, pushed their bikes for mile upon mile far into the night as a snowstorm, with 50-mph gusts, blotted out the trail. Skinny wooden trail markers kept many from losing their way.

Faced with such conditions, snow cyclists jokingly refer to their rides as “luggage racks.” Pontis once won the Susitna 100 by pushing his bike 56 miles – just over half the race – across the Alaskan backcountry.

“At a point the physics are against you and you have to accept your fate and march,” said Dave Gray of Surly, who helped design the Pugsley.

As veteran riders know all too well, long snow bike races generally involve some degree of pushing. Of the handful of U.S.-based contests, the most extreme has been held in Alaska for the past two decades.

The Iditarod Trail Invitational gives riders the option of biking 350 miles up the famed sled-dog route, or cycling the entire 1,100-mile course across frozen rivers, tundra and two treacherous mountain ranges all the way to Nome. The race started Sunday.

“I like it when the conditions are tough,” said Pierre Ostor of St. Paul, Minn., who hopes to reach Nome for the first time this year after three failed attempts. “It’s a mental game. I want to see whether I can be stronger than other people who may be faster bikers, but don’t want to get off and push their bikes.”

The 51-year-old Ostor designs bike tools and organizes Minnesota’s premier snow bike race, the Arrowhead 135.

At least two snow bike races made their debuts this year in other states. Byers put on the Togwotee Winter Classic, a 25-miler in the mountains of the Teton National Forest. The TripleD in Iowa covered the 60 miles from Dubuque to Dyersville and back.

Dead season no more

As the sport grows, some bike shop owners in northern climates said they no longer view winter as a dead season. Greg Matyas opened his Anchorage shop, Speedway Cycles, last summer. He said business has remained brisk through the cold months.

“We had studded-tire riding early on,” said Matyas, who helped design a new and much-praised snow bike model called the Fatback. “When we started getting snow, the fat-tire season picked right up.”

The new generation of snow bikes is a huge improvement from the days when die-hard winter riders would fuse rims and sew tires together in their garages in the quest for a powder-friendly ride.

“In the early ’80s we talked about putting skis, belts and all types of different traction devices on the bikes,” longtime Anchorage cyclist Steve Baker said. “People were just floundering around out there on regular bikes.”