Mutant Approved: The Fatback 29+

Splitting the tire difference

The growth rate of fat bike sales is staggering. It is estimated that out of the 20,000 fat bikes on the trails today, about 80 percent were purchased in the last 18 months. While this segment of mountain biking is still in its infancy, there are already mutations of the original 3.5-inch-wide tire fat bikes. Dubbed 29+, these bikes are designed to straddle the line between 29ers and fat bikes. The American-made Fatback 29+ out of Alaska is one such offering.

A better question is, “Where is it made for?” The Fatback 29+ is definitely a trail bike, but where it will shine is in areas where riders have to contend with ultra-soft trail surfaces (think deep sand, gravel and snow). The Fatback 29+ has the ability to navigate trails that have never been possible on a mountain bike. Think rock crawler.

The aluminum frame and fork are made in the United States. The bike uses a tapered headtube and sports a dropped top tube design to allow for more standover height. The frame accepts a direct-mount front derailleur, although ours skipped the front derailleur in favor of a 1×10 drivetrain. The frame has mounts for a fender or rack, and cable and hose guides are well positioned.

The wheels! The Surly Rabbit Hole rims and Knard tires steal the show on this very basic rigid bike. Mechanical disc brakes keep things simple, and the Race Face cranks with a single ring look very much at home.

The setup: There is not much to adjust except the tire pressure, which is probably too high. These giant-volume tires run single-digit psi levels; 3 or 4 psi is not out of the question.

Ergonomics: We were surprised the bike stayed out of the rider’s way. We expected some leg-to-stay rubbing with tires this wide, but it didn’t happen. Fatback used their fat bike experience (they make the real thing, too) to cleverly tuck everything in tight while still offering plenty of tire clearance (surprisingly more than on many conventional mountain bikes).

Moving out: The surprises continued. We expected lethargic acceleration, but the bike is surprisingly peppy. No, it is not as responsive as a conventional 29er trail bike, but it is not like an anchor either.

Cornering: The geometry lends itself to tight and twisty trails and there is no way these tires are going to let go on the technical stuff. It is so fun to negotiate loose, rocky and sandy corners feeling like you are riding on moist, tacky terrain. The real fun begins on fast corners where, when you allow the tires to get past their limit, the bike drifts with a confidence and control that will have the rider laughing.

Climbing: Again, not as bad as expected. The big rear tire offers so much traction that out-of-the-saddle attacks work if you have the lungs, heart and legs. And, you will need to get out the saddle with the very tall low gear of 6.7-feet per crank rotation.

Descending: The big tires help take some of the sting out of downhills, but you never forget that you are riding a rigid bike. The tires do offer a degree of suspension, but it’s suspension without any rebound control. That means riders need to keep their speed in check or the tires will begin to bounce like basketballs.
The bike really needs nothing. It is ready to roll. One word of warning for riders who plan to use a 29+ in winter conditions: Most groomed snow trails will not welcome 29+ bikes. This is also true for most trails groomed especially for fat bikes. The 29+ tires are well below the minimum width of 3.5 inches.

Remember, 29+ bikes get flat tires, too. Carrying a spare is a bit of a pain. Not so much because of the weight as the size.

Where mountain bikers enjoy great traction and easily negotiated trails (like in Southern California), the 29+ would only make sense as a second bike to play with. For riders who constantly struggle to maintain traction and control on the trails available to them, the 29+ is an answer to their prayers. It can make unridable trails ridable to a degree you could never experience from the saddle of your conventional mountain bike.