Another new wheel size and spec may come across as a gambit from an industry desperate to sell more gear. We appreciate—and empathize—with consumer frustration about the constantly shifting parade of “standards.” However, after more than a year on nearly a dozen bikes equipped with plus-size rubber, we’re here to say that this is no marketing gimmick.
We haven’t had this much fun riding mountain bikes in a long time (starting with last year’s Bucksaw). And while there are a handful of great new offerings in the size (from Trek, Santa Cruz, Salsa, Scott, and others), the Stumpjumper’s massive tire clearance and innovative frame design won over pretty much every tester who tried it. Said one grudging downhiller with a longstanding aversion to Specialized: “I didn’t want to like this bike. But it’s so capable and so much fun to ride, that you just can’t deny it.”
The Good: The time-tested Stumpy suspension paired with mid-fat tires is as cushy as an air mattress but still stiff when you need to power. The house-brand tires are some of the best plus-size on the market. Tire clearance is ample. And the SWAT frame design, with storage inside the down tube, is pure genius.
The Bad: At this price, we’d expect a carbon rear triangle (not alloy), which would help with weight. Aggressive riders might prefer a more progressive suspension.
The Verdict: Plus-size bikes, with wider tires than your average MTB but less girth and heft than a full fattie, are going to transform the market. They grip like Velcro, roll like wagon wheels (and 29ers), and, thanks to innovation on the rim and tire side, don’t weigh much more than a standard setup. And this mid-fat iteration of the Stumpjumper FSR—one of the longest running and most refined bikes on the market—is our hands-down favorite.
- Price: $8,600
- Components: SRAM XX1 drivetrain, 150mm Fox 34 Plus Factory, Roval Traverse SL rims
- Weight: 28.6 pounds
Mating Specialized’s highest-grade carbon front triangle to an M5 alloy back end, the Stumpy 6Fattie gets 135 millimeters of plush, rear travel. That’s middle-of-the-road for a do-everything trail machine, but this bike rides and feels much bigger courtesy of the three-inch tires. Rims are 27.5 inches around, but the extra rubber pushes the wheel diameter to within a few millimeters of the Stumpjumper FSR 29. (Yes, in addition to the 6Fattie, Specialized is still making Stumpjumpers in both 27.5 and 29—more on that in a bit.)
The comfortably slack 67-degree head angle put us in position to handle big obstacles just fine, but Specialized still kept the chain stays reasonably short (437 millimeters) for quick accelerations and totally solid pedaling manners. And unlike many of the plus-size models being launched, Specialized didn’t scrimp on clearance, with so much space around the back tire that we wondered whether there’s not room to tighten it up. That’s no criticism: we appreciate that the Stumpy will accommodate any plus-size tire on the market, as well as most 29ers.
Built around a custom-tuned Fox Float Factory DPS shock, including Specialized’s Autosag mechanism that allows for quick set-up by equalizing the pressure for you with a single button, the Stumpy is quite a soft ride. A few of the hardest-charging testers said they would have preferred that the leverage rate ramped up a bit more at the bottom of the stroke, but the vast majority of riders appreciated the squishy comfort.
Other than the tire size, what sets the frame apart from past Stumpjumpers is the SWAT storage. A hatch door behind the water bottle cage on the down tube snaps off to allow gear stowage inside the down tube. The space is equipped with two neoprene sleeves, which you can use to wrap tubes, tools, and a pump—all of which can be loaded into the bike. It’s one of those slap-your-head simple ideas—no more strap-on bags on your seat; no more getting caught out without a flat fix—but took some delicate engineering to maintain the bike’s strength and integrity. The design also added just under 200 grams to the overall frame weight, but we’ll happily take that tradeoff for the convenience.
Being the top-level S-Works model, this bike makes no compromises on parts. The SRAM XX1 drivetrain could have been undergeared for this big a bike, but Specialized wisely spec’d a 28-tooth ring. The 150-millimeter Fox 34 Plus Factory fork feels buttery smooth and perfectly suited to the task, with the thicker stanchions providing the needed stiffness. At one point during the test, we threw on a Fox 36 for comparison and enjoyed how aggressive it made the bike feel—but for daily use, the 34 is just right.
We had some initial concerns that the carbon Roval Traverse SL rims, with their 30-millimeter internal width, might be too dainty for these big tires, but we were proven wrong. These rims provided ample contact from the tires, and we appreciated their lightweight as they spun up nearly as fast and easily as a standard 29er, even with all that rubber. Given the newness of plus-size bikes, the industry is still debating over the optimal rim (and tire, for that matter) width for bikes like this one. We don’t know what the answer is, but we were fine with 30s in this application and would argue (as have some other manufacturers) that less is more for the weight saved (Specialized does offer a 38-millimeter-wide version for those who want more.)
The tires were another standout. The meaty Purgatory Control tread up front and lower-profile, faster-rolling Ground Control rear was a perfect combination for our chunky terrain in the Rockies. The casings are quite supple, which allows for a soft trail feel and good spread on the tires. But we were also surprised how durable they were, with zero pinches or sidewall cuts in well over six months, which is pretty rare in rocky testing grounds like Sedona and Phoenix. Alongside the Maxxis Rekon+ and the Bontrager Chupacabra, these are some of the best plus-size tires on the market.
Specialized also debuted its three-stage Command Post IRcc on this bike, which trades a fixed height at the middle setting for a 10-stop, 50-millimeter, micro-adjustable range. The stops make it easier to get into the middle setting, which some riders found difficult with the set height of previous iterations. We also applaud Specialized’s new commitment to spec’ing dropper posts on every one of its trail bikes, even the least expensive models. We agree this should be standard equipment for all riders other than flat-out XC racers.
The Stumpy 6Fattie might have three-inch tires, but it doesn’t ride heavy or slow. Thanks in part to those gossamer carbon rims, this bike felt lighter than its 28.6 pounds suggested—and quicker than bikes that weighed several pounds less. The suspension design is one of the most tried and tested on the market, and together with a careful shock tune, it pedals exceptionally well, with little bob or energy loss. Some testers noted how the low bottom bracket led to frequent pedal strikes, particularly on the larger frames, which have the same BB-drop as the smaller ones. On the other hand, the low geometry added stability and meant the bike tackled drops, chutes, and big obstacles much more handily than we expected from the 135mm rear end.
The geometry and suspension are dialed, for sure, but it’s the wide tires that make the bike so capable. The extra rubber, which we ran between 14 and 17 psi, claws at loose ground and is all but impossible to cut free in turns. The tires skipped through big chunder and rocks, a mainstay in New Mexico and Arizona, and they felt like they had near suction power on slick rock passages. The Stumpy made technical bits so easy and fun that when we went back to 2.4 tires, they felt anemic and a bit scary in the rough. That’s the other thing we liked about this bike: you can throw on 29-inch wheels (provided they have Boost hubs) and the bike gets speedier, making it effectively like two rides in one.
Other than cultural resistance, it sort of makes us wonder why Specialized even sells the Stumpjumper FSR in 29- and 27.5-inch versions. The company says the 27.5 is for playful riders, the 6Fattie is for control, and the 29 is for speed—but honestly the only terrain where the 6Fattie left us wanting a bit was on wide open dirt roads. And given that there’s a women’s version—the Rhyme 6Fattie—even the argument about smaller wheels being better for smaller riders seems to go out the window.
Our advice: Go 6Fattie. And if you really want more versatility, pony up for a set of spare 29-inch hoops. Truthfully, though, we never wanted anything but the plus-size tires, even on smooth, fast, flowing trails. The traction and cush is just that much fun.
The Stumpy 6Fattie won Gear of the Year for 2016 (the Buyer's Guide is on newsstands now), but it was a tight fight with the Santa Cruz Hightower, which is another shape-shifter that can accommodate both 27.5+ and 29-inch wheels. The Stumpy’s added tire clearance and unique SWAT frame design put it over the top, but the Hightower’s stiffer, more progressive suspension definitely appealed to the DH-oriented testers in our ranks.
Beyond those two options, we rode a handful of excellent plus-size bikes this year, including the playful Ibis Mojo (with tighter tire tolerances), the Scott Genius LT 700 Tuned Plus (the most aggressive in the bunch with 160 millimeters of rear travel), the all-around awesome Salsa Pony Rustler (with heavier wheels but a more affordable price tag), and the Rocky Mountain Sherpa (a great working-man’s bike that looks amazing.).
You wouldn’t go wrong with any of these bikes, but testers put the Stumpy 6Fattie above them all. At $8,600, the S-Works Stumpy 6Fattie is even competitive price-wise, with the comparable Hightower checking in for several thousand dollars more. Value aside, that’s still a ton of cash. But Specialized makes the bike in several specs, including an Expert 6Fattie for $6,500 and a Comp 6Fattie for $3,500. Frame geometries and kinematics are the same—it’s only the materials and parts that differ.
Plus-size is a development that may have a hard time quickly catching for the simple reason that bikes already work so well. However, what makes the 6Fattie so successful—and what we believe will eventually sell plus-size on the large scale—is that when you first climb aboard, it doesn’t feel abnormal or strange, but when you switch back to standard-width tires, you miss the added traction and comfort.
And the Stumpy 6Fattie isn’t just a great plus-size bike. It is the ultimate trail bike. It’s big and playful enough for most riders in 90 percent of terrain, but not so heavy and commanding that it feels overbearing. It’s the sort of bike that lets you, for reasons you can’t completely explain, rip a descent faster than you ever have or grind up some move that’s stymied you for years—and then almost forces you to whoop and shout out loud about it. In our book, the highest praise you can heap on a bike is that it lets you rediscover that youthful exuberance of riding again, and the Stumpy 6Fattie had us craving to ride more than we have in years
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