It was a frozen day in 2006 when I first swung a leg over the frame of a fat bike. The venue was the debut edition of the Arrowhead 135 Ultra, a race that traveled its namesake 135 miles through the snow in northern Minnesota. Back then, the large-tire bikes were freaks, and they were made only by custom frame-builders who liked to pedal in snow and a single Minnesota brand, Surly Bikes, which mass-produced the first notable bike in the “fat” genre with its Pugsley frame.
Wide rims, extra-large tires, and weirdly-dimensioned frames to make it all fit together define a fat bike, a cycling subcategory that’s garnered a serious following now in 2012. Bike shops report selling out of fat-bike stock. Brand managers at Surly and Salsa Cycles, another fat-bike maker owned by Minnesota’s QBP, have told me demand this year has overwhelmed supply.
What is the appeal? From improved traction on dirt to flotation when riding through snow, the obese tires let a bike roll where it has not rolled before. The wide rubber — some fatty tires are 4+ inches across, or twice as wide as most mountain-bike tire tread — adds notable grip on the ground, and the extra surface area does not allow the wheel to sink as much into soft surfaces like snow or sand.
Another distinction: You can ride with significantly lower tire pressure. Think 15 or 10 psi, or even lower still. This gives the tire some significant squish, and that play translates to more rubber conforming onto the trail for serious grip.
On snow, the wide tires have more surface area touching down and simply “float” a bit more rather than digging in like skinnier tires can. Finally, with all that squishy rubber under you, suspension is not necessary for most fat bikes. (Though Salsa recently revealed a not-for-sale dual-suspension fatty it is contemplating bringing to market soon.)
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