What sets 27.5+ apart is that it pairs a standard 27.5-inch wheel to a high-volume tire to get the same effective diameters as a 29er, while providing more traction for less weight.
What sets 27.5+ apart is that it pairs a standard 27.5-inch wheel to a high-volume tire to get the same effective diameters as a 29er, while providing more traction for less weight.

27.5+ Complicates the Wheel Debate

Even though we may not want another standard, there’s no denying that mid-fat is good—and it’s here to stay

What sets 27.5+ apart is that it pairs a standard 27.5-inch wheel to a high-volume tire to get the same effective diameters as a 29er, while providing more traction for less weight.

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After all the debate between 26-, 27.5-, and 29-inch wheels in recent years, probably the last thing any mountain biker wants is another wheel standard. But maybe the biggest news at this year’s Sea Otter Classic, the spring bicycle industry gathering and expo, is the emergence of the 27.5+. At least three companies are rolling out bikes with the new wheel size, and based on the proliferation of parts we’ve already seen emerge, including rims, tires, and forks, we expect more bike manufacturers to follow suit in the coming year.

The new size is a spin-off of the 29+ movement, which was launched three years ago by the iconoclastic Minnesota brand Surly with its groundbreaking Krampus. That bike had three-inch tires mounted on 29-inch rims and offered the traction and confidence of a fat bike in a lighter, nimbler package. Other models have followed, including the Niner ROS9+ and this year’s excellent, bikepacking-oriented Jones Plus, but some companies contended that the huge wheel circumference was too unwieldy to accommodate progressive designs.

What sets 27.5+ apart is that it pairs a standard 27.5-inch wheel to a high-volume tire—we’ve seen between 2.8 and 3 inches so far—to get the same effective diameters as a 29er. So why not just ride a 29er? Because the 27.5+, thanks to its large volume, provides tons more traction than a standard 2.4-inch 29er tire without adding as much weight in rubber as a 29+ or fat bike. Specialized, for example, says their testing shows that because the bigger tires can be safely run at lower pressures, they offer as much as a 69 percent increase in contact patch.

Rocky Mountain was the first company to jump into the 27.5+ game when they showed a handmade prototype of a full-suspension, bikepacking model, The Sherpa, at Sea Otter last year. That bike has been on the slow-boil development for a couple of years, and the company finally has a production-ready bike, which will hit stores next month. We have been pleading for someone to make a full-suspension mid-fat bike ever since we rode the Krampus, and from the looks of it Rocky Mountain has nailed the execution. (Lenz Sport produces a full-sus 29+ called the Fat Moth but were unable to provide one for testing as they were still tweaking the geometry.)

The Sherpa Overland will be the first-to-market full-suspension 27.5+ bike, aimed at the adventure riding and bikepacking crowd with 95mm of rear travel and 120mm up front. It was developed in cooperation with WTB, and the latter company’s 2.8-inch Trailblazer tires and 45mm-wide Scraper tubeless rims are appearing here for the first time together on a production bike. We’ve ridden the Scrapers, on the Jones Plus earlier this year, and we like the way the additional rim width lets the tire spread and grip the trail. The bike has a carbon front triangle and alloy rear end, and is equipped to run a front derailleur while still maintaining a standard Q-factor thanks to a custom spindle width. The Sherpa Overland will retail for $4,500. Rocky continues to show the bike with a range of custom packs for bikepacking, though those will be sold separately.

(Courtesy of Rocky Mountain)

Specialized’s new Fuse and Ruse (men’s and women’s) may look reminiscent of the company’s venerable Stumpjumper because of the hard tail design, but the bikes actually borrow a more trail-oriented geometry from the full-suspension Stumpy FSR. All have 67-degree head tubes, 120mm forks (except 100mm in the smallest sizes), and dropper seat posts all around. Specialized is branding its 27.5+ tire line, which it is launching with three-inch Ground Control and Purgatory models, under the name 6Fattie, a suggestions that the company could have more in store. The tires will roll on new, fatter Roval rims, with an inner width of 38mm, which the company says provide the sidewall support needed for the three-inch tires. For the moment, the alloy hard tails will come in three models each for men and women, from the Pro at $3,100 down to the Comp at $1,600.

(Courtesy of Specialized)

Finally, Jamis, which has been making 650B steel hard tails under the Dragon moniker for over a decade, is launching the Dragonslayer. “The Dragon is legend around here,” said mountain bike product manager Sal Crochiola. “We don’t take it lightly when we decide to put the Dragon name on a new bike model.” Like Specialized’s Fuse, this bike is a fairly slack, trail-oriented hard tail with three-inch tires and a 120mm fork. It is 2x compatible and runs Vittoria Bombolino tires on WTB’s Scraper wheels. There’s no word on pricing yet, but, based on the spec and Jamis’ reputation for value, the Dragonslayer is bound to be relatively affordable.

(Courtesy of Jamis)

Naysayers may poo-poo yet still another standard, and ordinarily I’d be sounding the same complaints. But having had the chance to ride some 27.5+ wheels for the past few months (a pair of Specialized 6Fatties mounted with Ground Controls, to be exact), I can say this is not just marketing hype. The semi-fat tires provide incredible traction—akin to our favorite fat bike, the Salsa Bucksaw —but at less of a weight penalty. This width has the potential to reinvigorate the hard tail market as the extra tire girth goes a long way to smoothing out the ride. And on full-suspension designs, the semi-fat tires provide technical prowess and confidence that is miles beyond a bike with standard size rubber.

Admittedly, 27.5+ won’t appeal to everyone and it’s not going to obsolete the other popular standards (at least not quickly). But this new size continues to make the pretty convincing argument, as fat bikes have made as they have matured, that a broad section of the market can benefit from bigger tires. It doesn’t even seem like a stretch to think that one day not too long from now, we may be laughing about “skinny” 2.2-inch tires the way we today chuckle over rim brakes and the original 1.9-inch suspension forks. 

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