Fat tires, slim choices

Jan 10, 2017

Mike Pritchard of the Roaring Fork Mountain Bike Association rides the Aspen Fat Bike Loop. Pritchard is working on getting more trails open to bikes in the winter.
Credit Elizabeth Stewart-Severy/Aspen Public Radio News

The Roaring Fork Valley is a biking wonderland in the summer months, rife with world-class singletrack trails and scenic, quiet roads. But in the winter, it’s a different landscape. Local mountain bikers are working to change that.

Aspen’s in-town option for winter biking is about 4.5 miles long, dubbed the Aspen Fat Bike Loop. It includes plowed bike paths and two short stretches of groomed singletrack that Mike Pritchard of the Roaring Fork Mountain Bike Association calls “the holy grail” of fat biking.

Fat bikes, so-called because of the enormously wide tires, are designed for riding on packed snow. The 4 to 5 inch wide tires have more traction on soft snow than regular mountain bike tires. But they aren’t magic.


“You can’t just head out into a field of powder. They’re not like skis,” Pritchard said. “You really need a compacted surface.”

So winter cyclists look for trails that are groomed or see lots of hiker traffic, but perhaps most important in choosing your route is remembering where not to ride.

“There are a lot of great Nordic trails,” Pritchard said. “It’s tempting to get on there, but we’re developing this fat bike loop and other opportunities so that we’ve got our legitimate places to ride.”

Right now, those spots are pretty limited. Nordic trails are off limits because wide tires have a tendency to leave ruts, and most of those routes are designated for skiing — not cycling. The entire White River National Forest is also out of the question because of the forest-wide winter ban on wheeled vehicles, including bikes.

Kay Hopkins, recreation planner for the U.S. Forest Service, said the agency doesn’t see a major problem with fat bikes.


“We never analyzed mountain biking in the winter,” she said. “It’s a relatively new use in the landscape.”

Pritchard is heading up the effort by the International Mountain Bicycling Association (IMBA) to amend the broad ban. He’s drafting a proposal to allow fat bikes on certain trails in the White River National Forest.

“We think we’re going to be successful because we’re really asking permission to ride fat bikes where bikes can go in the summertime, where people are already prevalent in the winter time, and especially where snowmobiles are allowed to go in the wintertime,” Pritchard said.

The focus on trails that already see heavy use is key, especially in protecting wildlife habitat.


“There’s only so much landscape out there, right?” Hopkins said, noting that critical winter range is particularly scarce.  “Those are some of the last pieces of the landscape that those animals have left.”

Those animals include the Canadian lynx, which is listed as a threatened species under the Endangered Species Act. Lynx have an advantage over other predators in the winter because their large, furry paws are well adapted to deep snow. More groomed areas would mean reducing key habitat, so the proposal from IMBA will only consider areas that are already compacted.

Pritchard is working with fat-bike enthusiasts across the White River National Forest. His proposal for local trails will include Maroon Creek Road, which is now technically off-limits to bikes in winter, Independence Pass, more of the summer trails up Smuggler Mountain and some routes to 10th Mountain Division Huts.

And, in the meantime, he’s working on developing rapport with all other users, especially as he prepares to ask snowmobile organizations for access to their trails.

“Just like with any mountain biking actually, you’ve got to act responsibly, otherwise we’re going to lose our access,” Pritchard said.  

This means not biking when it’s too warm because the tires leave big ruts and making sure to yield to everyone else on the trail.

Pritchard aims to have the proposal finished in the next couple of weeks, and the Forest Service will then complete an environmental assessment.

Cyclists interested in trying out the local loop can check out a free fat bike demo during Winterskol activities Saturday, Jan. 14, at Wagner Park.