WINTHROP — Anything this obscenely fat is bound to draw stares, especially in Washington's Methow Valley, where it sometimes seems as though everything from the people (ultra active) to the skis (Nordic) are skinny.

WINTHROP — Anything this obscenely fat is bound to draw stares, especially in Washington's Methow Valley, where it sometimes seems as though everything from the people (ultra active) to the skis (Nordic) are skinny.

I could feel the stares as soon as we unloaded our bikes at the Big Valley trailhead about seven miles west of town.

We were heading out on the Methow Valley Sport Trails Association trails on fat bikes, the latest fad in cycling and snow sports.

Fat bikes are essentially mountain bikes with low-pressure, motorcycle-size tires that allow riders to pedal over compacted snow.

"Remember when you were a kid and you got a Big Wheel and you felt like you were invincible, like you could go anywhere?" said James DeSalvo, the association's executive director. "That's what you feel like when you are on a fat bike. You just bounce over curbs and pot holes and keep going."

I understood what DeSalvo meant as soon as the 4-inch-wide tires on my rented orange Salsa Mukluk hit the snow. I'd never consider this on my mountain bike, but now I felt like I was floating over the snow.

Clearly we looked as interesting as I felt, because less than a mile down the groomed trail I felt the looks again. Two couples from Seattle out for a hike couldn't believe what they were seeing.

"Want to give it a try?" said Kristen Smith, the association's marketing director. At first they politely declined, but wanted to know more about the bikes. After awhile, Smith offered again. This time the husbands hopped on while their wives took pictures.

When they pedaled back a few minutes later, all four posed for pictures with the funny-looking bikes.

"One of the guys at the bike shop says riding a fat bike right now is almost like getting your 15 minutes of fame," DeSalvo said. "Heads are turning. People stop you to ask questions. For those few minutes, you get to be a hero."

"Hero" might be a little strong. You might look a little different, but the truth is this sport is quite easy.

"Whether you're athletic or unathletic, if you can ride a bike, you can ride a fat bike," DeSalvo said.

My riding partners on this unseasonably warm (about 30 degrees) morning should definitely be classified as athletic. Smith, Ed Stockard and Joe Brown all enjoy logging miles on their fat bikes.

Brown, co-owner of Methow Valley Cycle and Sport worked with the trails group to get the trail system open to fat bikes on a trial basis this winter.

He rents four bikes from his shop and says he's ordering more because he's having trouble keeping up with demand. The bikes sell for $1,700 or more.

When the bikes are returned, he says almost every customer raves about the experience.

"Your brain tells you it's going to be one thing, then you realize you're floating on top of the trail," Brown said. "It's pretty cool."

He added, "One thing I hear a lot from people who ski is that it's really fun to have a different experience on the same medium."

Brown compares the fat tires to "those big, squishy, go-anywhere tires you see on tundra trucks in National Geographic," and says they work well on almost any surface. Snow is most popular, but they travel over sand and rocky surfaces too.

The low tire pressure (10 pounds or less per square inch compared with about 60 psi on a mountain bike or 100 or more on a road bike) negates the need for a suspension system. Riders recommend playing with the tire pressure a bit until you find the best ride.

"If in doubt, let air out," said Steven Mitchell, perhaps the valley's most experienced snow rider.

Mitchell has been riding on snow for 25 years. In 1987, while he worked at a Seattle bike shop, he read an article about the Iditabike, an Alaskan bike race that followed a portion of the famous route used for the Iditarod dog sled race.

The next year he showed up with a standard mountain bike rigged with a ski. He needed 55 hours to cover the 200-mile course.

"But the fire was lit," said Mitchell, who owns Winthrop's Rocking Horse Bakery. "It was my first experience in the true wilderness without a soul around. I saw the northern lights. It wasn't like a race. It was a real adventure."

Mitchell ended up moving to Alaska and even organized the race in 1990 while continuing to participate.

Each year he and the riders got more and more innovative with their bikes, trying to make them travel better over the snow.

Mounting skis on the bike didn't seem to work. Huge knobby tires didn't work as well as ones with shallower tread.

Some started welding rims together to use wider tires only to learn the tires would come loose when the air pressure was super low. So, they started gluing the tires to the rims.

In 1991, Mitchell dropped his time to 26 hours by using a bike that had two rims welded together in the front and three in the back.

"We all learned from trial and error," he said. "We all thought we were pioneers, but really, everybody who lived in northern climates was probably doing the same thing if they wanted to ride on the snow."

Mitchell doesn't expect the sport to become as popular as mountain biking (although you could argue that it's a form of that sport), but he expects it to carve out its niche in the cycling and snow sports industries. "This fad may be less fad and more reality."