STORY AND PHOTOS BY KAREN BOSSICK

When Roger Mankus and Muffy Ritz took part in Island Park’s inaugural 60-kilometer fat bike race earlier this year, they found themselves trying to pedal through deep soft snow that was like trying to bicycle through quicksand.

The course had been groomed by snowmobiles, but a storm had dumped fresh snow on the course. Ritz toppled over a couple dozen times in the deep snow and Mankus did the same.

Ritz—a former American Birkebeiner champion--crossed the finish line only by sheer will, finishing the course in about seven hours versus what she says she would have done in three hours on skis. And Mankus finished behind her, as the short December day was turning dark.

The grueling race didn’t diminish their enthusiasm for fat biking, though. You’ll probably see the two out at the Sun Valley Nordic Center on Saturday competing in the second annual Snowball Special Fat Bike Race, which drew 75 riders last year with two weeks’ notice.

The event kicks off with a Fat Bike Expo and a chance to test the course for a $10 trail fee from 2 to 5 p.m. today—Friday, Jan. 29. The 20k, 40k and 40k relay races will run from 10 a.m. to 3 p.m. Saturday, Jan. 30, on a specially created course that includes the White Clouds and Boundary Creek trails.

“Fat biking is the biggest fastest growing segment of the bike industry,” said Mankus, who works at The Elephant’s Perch in Ketchum. “Sales have doubled every year for the last three years.”

Fat biking in the Wood River Valley started a few years ago with a few bikers riding four- and five-inch tires up and down the Wood River bike trail as they commuted between Hailey and Ketchum. The Blaine County Recreation District responded to the growing interest last year by creating a new Durrance Loop for bikers and skiers near SNRA headquarters.

Sun Valley Nordic Center opened its Dog and Boundary loops to fat bikers this winter. And national mountain bike champion Rebecca Rusch teamed up with Bigwood Golf Course to offer six miles of single-track loops around the greens.

“When it all started, we basically had mountain bikes with bigger tires,” said Bob Rosso, owner of The Elephant’s Perch. “As the tires became bigger, they did less damage on the trail, so there wasn’t as much contention between skiers and bikers.”

Ketchum firefighter Tory Canfield says the Fat Bike Advocacy Group of the Wood River Valley Bicycle Coalition is trying to get more terrain opened up. Proceeds from this weekend’s race will go to the group.

“It’s an awesome alternative sport. I love riding around town in winter and I like to get out and explore, too. Adding snow to the trails completely changes the biking experience,” she said.

“You have solitude and quietude,” added Mankus. “Everything looks totally different. And it’s a way to extend the biking season since it lets you bike year round. I just find it nice to be out there in nature in winter on a bike.”

EJ Harpham, another winner of the legendary 55-kilometer American Birkebeiner Nordic ski race in Wisconsin, was among the first in the Wood River Valley to try fat bikes.

She says snow biking is less intimidating than mountain biking with all its rocks and stumps because everything is covered in snow.

“It’s like powder skiing. Instead of 120 pounds of pressure in your tires, you’re riding with eight or nine pounds of pressure—sometimes even less than that. And it gives you a spongy, springy feel as you cruise along,” she said. “It’s great for those days when the snow is so cold that skis don’t want to glide on the snow. It’s a good workout. And it’s so much fun. I’ve gone over the handlebars and gone poof. But landing in the snow is so soft you just laugh.”

Rosso said the first batch of Specialized fat bikes he ordered this winter sold immediately. And it was difficult to keep the rental bikes, which rent for $55 and $45 a day, in stock during the Christmas holidays.

Summer bikers often question how you can keep warm riding a bicycle during winter, Harpham said. You’re riding slower so you don’t get the wind chill you would at summer speeds, she said. There are special clothes for winter biking, as well.

Mankus, for instance, uses Cobrafist mitts that go over his handlebars to protect against the cold. He also wears 45NRTH cold-weather cycling boots made of Primaloft that are outfitted with liners and a carbon midsole that can withstand temperatures down to minus 31.

“You want to dress a little warmer for fat biking than you do for Nordic skiing,” he said.

The bikes themselves cost between a few hundred dollars and $9,000, with the more expensive bikes featuring lightweight all-carbon frames.

The basics of riding are much the same as for mountain biking, said Jennifer Biondi, a bicycle instructor at Galena Lodge.

“Keep equal weight on your tires. Look where you want to go. Switch gears. When you climb a hill, lean forward to get more traction on your front tire. You may feel a little squirrely or like you’re slipping a big if the snow’s real soft. But get your weight right and it’s fun,” she said.

Do remember, however: The snow is constantly changing so you have to adapt, said Rusch.

Fat bikes work best on trails that have been packed down by snow groomers, snowmobiles, cars or other bikers. If you’re leaving a rut deeper than an inch, the snow is too soft and you shouldn’t be riding.

Fat bikes should yield to skiers.

“Don’t poach the trials,” Rosso urged. “If everybody works together, the more we’ll see happen and the bigger the smiles we’ll see on everyone’s faces.”