Fat-tire bikes (or fat bikes, for short) really catch the eye. Their bulbous tires, upwards of 4 inches wide, seem to belong on a very different vehicle—a moon rover, perhaps, but definitely not an otherwise normal-looking mountain bike frame. Yet these bikes have exploded in popularity over the past few years, creating year-round, all-terrain riding opportunities.
The characteristic large tires are inflated to a low pressure, under 10 psi, while a traditional mountain bike tire might be inflated to five times that. This wide, forgiving base allows cyclists to roll over rugged trails and to avoid sinking into soft surfaces such as snow, sand, and mud. “Even if you’re not a very technically skilled mountain biker, the fear factor is taken away with fat biking because you glide over everything,” says Marcy Schwam, an AMC member who rides her fat bike on parts of the Bay Circuit Trail and on beaches north of Boston.
The fat bike phenomenon picked up speed slowly. Tinkerers began adapting mountain bikes to ride on sand and snow in the 1980s, but such bikes weren’t available in stores until 2005, when the Minnesota-based manufacturer Surly released the Pugsley. Although sales have increased between 15 and 45 percent each year since, it took several years for the fat bike to become mainstream enough that even industry insiders stopped asking what the comical-looking bikes were for. “The 2014 trade-show season was the first year I never had to answer the question,” says Tyler Stilwill, marketing manager for Surly.
Many companies have now joined Surly in this niche market, including the major manufacturers Trek and Specialized. Fat bike sales grew 44 percent industry-wide from 2013 to 2014, according to Bicycle Retailer and Industry News. Suddenly fat bikes are a regular sight: crawling through snowy trails, cruising down beaches, even rolling along slushy city streets. Land managers have taken notice and have begun adapting to the demand.
Joseph Hines, a trail builder in Carrabassett Valley, Maine, first noticed fat bikes about three years ago. “The best thing about fat bikes is they allow you to ride year-round,” he says. “There is no off-season and a very short window of mud season. Overall the fat bikes do not damage the trails. They are often easier on them.”
Fat bikes do raise some Leave No Trace (LNT) concerns. They allow access to terrain that other bikes don’t, making it easier for less experienced cyclists to get off-road. But the same rules apply to fat bikes as to traditional mountain bikes: Cyclists should stay on designated mountain bike trails and avoid delicate terrain or potential animal habitats, such as sand dunes.
Tim Tierney, executive director of Kingdom Trails, a mountain biking and Nordic skiing facility in East Burke, Vt., recalls seeing his first fat bike at a winter event the site hosted five years ago. Within two years, he says, the bikes had caught on. Kingdom Trails now maintains separate winter trail networks for skiing and for mountain biking. The staff even grooms the trails differently, using a narrow snowmobile to create single-track for the fat bikes.
“We realized we had to start managing for this and maintaining for it,” Tierney says of this past winter, when Kingdom Trails saw a 50 percent increase in winter cyclists. “We realized, this is here to stay—this isn’t a fad.”