The swelling popularity of fat-tire biking in the wintertime has the U.S. Forest Service working with local mountain-bike groups on a potential proposal for new routes where they would be allowed.

Mike Pritchard, executive director of the Roaring Fork Mountain Bike Association, said he expects slow progress to continue this winter on the study of new paths that may be acceptable for fat-tire bikes.

He said fans of the bikes would love to use them on the road to Independence Pass and up toward the Maroon Bells. His group has been studying such places in particular because they see a great deal of use from snowmobilers and pedestrians. Both groups play key roles in grooming and compacting the snow that fat bikers need.

“Fat bikes are not powder machines,” Pritchard said.

But no new groomed routes are being proposed in the White River forest, as that would take additional study of impacts on lynx and other environmental concerns.

With bike shops and the Aspen Nordic Center offering fat-tire bikes for rental, one proponent, Erik Skarvan of Aspen, said it’s past time local governments addressed where the bikes can be used. He runs a guide business that instructs people on fat-tire bikes in the winter, and said where they are allowed is somewhat of a gray area.

Currently, fatties are limited to plowed routes that are open to wheeled vehicles or designated routes that are open by a special order, says a Forest Service press release.

“All trails are closed to fat-tire bikes in the winter in accordance with the White River National Forest 2011 Travel Management Plan,” says the release issued Tuesday.

But many county roads that are plowed cross wilderness areas in the massive national forest, Skarvan noted.

And the sheer scale of the 2.3-million-acre White River forest is “what’s taking time here,” Pritchard said.

His group has been reaching out to stakeholders for input. Another issue is confusion over what entity is responsible for certain routes. Maroon Creek Road, for instance, is managed by Pitkin County, but the Forest Service closes it during the winter, while T Lazy 7 employees actually groom it beyond the closure gate.

Each potential route is “a custom negotiation,” Pritchard said.

Such jurisdictional issues also exist closer to town, with the bikes being banned from trails that cross easements on which mechanized vehicles are prohibited.

The Aspen Snowmass Nordic Council has banned the bikes from all nordic trails, save for a loop between the Aspen Golf Course, Marolt Open Space and the Aspen Recreation Center. Skarvan said that’s understandable: Nordic skiers don’t want to be tripped up by the deep ruts the bikes can leave.

Pritchard agreed, saying fat bikers need to use the right equipment and learn when the time is right to go.

“If you’re leaving a rut, it’s time to get off, you’re ruining it for everybody,” he said.

But places such as Crested Butte and Park City do allow fat tires on their nordic systems — to the point where officials are beginning to market that availability, Skarvan said.

The city of Aspen, when conditions warrant it, creates the 3-foot-wide loop using a specialized groomer. Skarvan, however, said the snow can only stand up to the tires for two or three months in the winter.

His business employs the multi-use Rio Grande Trail for fat-tire bikes, mostly from Stein Park to the Woody Creek Tavern.

Pritchard said he believes that anywhere snowmobiles can go, fat bikes “can probably go there and get along.” He predicted the local acceptance of the bikes will grow — he noted no tickets have been issued for people riding fat bikes in prohibited places — though that’s likely still a few years away. In the meantime, the Roaring Fork Mountain Bike Association wants to establish GIS coordinates for possible routes to give the public a better sense of locations.

“We think there’s a reasonable change in the rules to be considered to allow for winter fat biking,” Pritchard said.

Chad is a Contributing Editor for Aspen Daily News. He can be reached at or on Twitter @chad_the_scribe.

Contibuting Editor