(Photo: Jen Judge)

6-Month Review: Specialized S-Works Fatboy

Behold the epitome of the new fat bike: fast, fun, and astonishingly light


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Five years ago, when I wrote my first review of the Surly Pugsley, which is still an excellent but very different bike, I never would have imagined that anyone could build a fattie as light, responsive, or ridiculous as this Fatboy. It truly is a work of engineering mastery.

The Takeaway

(Jen Judge)

​The Good: At 23 pounds and change, this carbon race machine is lighter than many skinny-wheeled hardtails and redefines how we think about fat bikes. The HED Big Deal carbon wheels spin up as quickly as XC rims, and the 4.6-inch Ground Control tires easily set up tubeless, feel surprisingly light, and shed mud and snow admirably. The 28-tooth chainring is the smart spec for 1×11 on a bike built for snow.

The Bad: ​We had an issue with the rear SRAM Guide brake constantly getting air in the lines. We’re hoping that’s an anomaly. Mostly, though, there’s nothing to dislike other than the astronomical $7,500 price, and even that is mitigated by two lower-spec models, which get you the same frame for less. (Expert, $5,400; Comp, $2,900.)

The Verdict: The S-Works Fatboy is a study in possibility, pairing cross-country race manners and characteristics to fat bike dimensions. We can’t think of any bike we’d rather race over snow. Even on tight singletrack and rocky, techie trail, the bike holds its own alongside pretty much any XC machine. It’s crazy expensive, yes, but for the aficionado living in very snowy climes who rides snow bikes every day or the racer looking at events like the Arrowhead or Iditarod Trail Invitational, you’d be hard-pressed to find a better rig.


  • Price: $7,500 
  • ​Weight: 23.1 pounds
  • ​Build: SRAM XX1 drivetrain, Race Face Next SL crank and seatpost, Specialized carbon bars, and HED Big Deal rims laced to DT Swiss Big Ride 350 hubs

The Frame

(Jen Judge)

Specialized has been building carbon frames for well over a decade and has perfected the process. With a huge, chunky bottom bracket and vertically oriented rectangular chainstays cut thick, the bottom of the frame transfers power incredibly well. Meanwhile, the top tube and seatstays are minimal and flattened for ride compliance. There are hex-driven thru-axles front and rear, three sets of bottle bosses (including a triple configuration on the down tube). and a mount for a chain guide if you care to run one. The cabling is all internally routed through beautifully sculpted stops. Mud and snow clearance is enormous, especially on the front carbon fork, with spacing that dwarfs the 4.6-inch tires.

(Jen Judge)

The geometry is decidedly race-oriented, including a short, steep (70.5-degree) headtube and a low bottom bracket with plenty of drop. In fact, there’s not much difference on paper between the Fatboy and Specialized’s full-fledged racer, the Stumpjumper HT, other than longer seatstays to accommodate those big tires and a slightly bigger footprint (the wheelbase is 35 millimeters longer in the size medium). The two bikes aren’t far off in weight, either, with about 200 grams separating the two. Even with that longer rear end, somehow the Fatboy still feels plenty quick to accelerate and nimble in tight spots.

The Build

Every part on the Fatboy is premium, from the SRAM XX1 drivetrain to the Race Face Next SL Crank, seatpost, and Specialized carbon bars. Even the saddle, a Body Geometry Carbon Phenom Pro, is top shelf: it weighs 193 grams and retails for $200, and yes, it’s pretty damn comfortable to boot. There’s even a SWAT bottle cage, meaning you’re never without a small multitool to remove the wheels.

(Jen Judge)

Though I have misgivings about single-ring drivetrains, mostly surrounding the decreased gear ratios, they’re ideal for fat bikes, in part because you can gear low and get away with it since the speeds and torques aren’t as demanding. And because of the likelihood of running into mud and snow that can pack out and freeze up the gears, the lack of a front derailleur means one less part that could potentially fail. We did notice that in heavy muck, the chain had a tendency to hop off the front ring, so a chain guide like an MRP 1x could be a good idea.

The wheelset—85-millimeter-wide HED Big Deal rims laced to DT Swiss Big Ride 350 hubs—is the standout performer of the entire package. Lighter than most comparable tubed aluminum setups by 1.5 to 2 pounds per wheel, they are probably the biggest single factor in making the bike feel quick and light. The added stiffness you get from the carbon also helps with tracking and line choice, especially since fat tires already have so much inherent flex and give. Also, kudos to Specialized for the Ground Control tires, which have large, grabby knobs that work well for both techie trails and snow but also slough off mud and slop.

The only slight misfire we had was with the SRAM Guide RS brakes, which until now seemed like the recovery the company has needed from its disastrously unreliable line of brakes. Indeed, stopping power and modulation are excellent. However, our rear brake repeatedly lost pressure and needed multiple bleeds during the test period. Hopefully, it’s a one-off problem, but we’ll keep a closer eye on the Guides on all our test bikes moving forward given the company’s history.

The Ride

We spent the first months aboard the Fatboy on dry trails around Santa Fe and Albuquerque. Fatties generally thrive on the loose and rocky singletrack here, but this one did especially well. It was a treat even on trails with some of our steepest climbs: the big tires gripped the loose, rocky stretches without adding the usual fat bike heft. On one of the techiest climbs in Santa Fe—a three-mile, 1,800-foot ascent littered with boulders, step-ups, roots, and very steeps—I floated through sections that are normally difficult or impossible, thanks to the extra grip. Descending the other side wasn’t as casual, but even with no dropper and a fairly steep head angle, the bike made pretty easy work of some sketchy drops and roll-ins.

(Jen Judge)

As well as it did on the trail, the Fatboy was even more composed and at home on snow. Whereas many fat bikes seem ponderous and excessive, which the rolling resistance of snow can exacerbate, this bike feels sprightly and almost impatient—even with six or eight inches of fresh. It’s like the peppiest of XC race bikes, only with major tires and traction. I piloted it to near the 12,000-foot summit of Ski Santa Fe in not much longer than it takes me on a standard hardtail on dry trails, and then savored the long descent. Yes, it was a bit twitchy on the steep descents and snowshoe-pocked trails, but that’s to be expected of a race bike.

That’s the thing to remember: the Fatboy, especially in its S-Works form, is definitely made for going fast and hard. Other bikes out there are slacker and more comfortable and might plow along better than this one, but if you want to crush snowy trails—and even some dirt and tech—the Fatboy is a great option. In fact, we wonder whether it wouldn’t double as an amazing XC race bike if you laced up a second pair of wide hubs with carbon rims—perhaps the perfect impetus to downsize and chuck out the hardtail in the fleet.

The Competition

(Jen Judge)

The array of fat bikes is huge and still ballooning—even in the race bike realm. Probably the best comparison is the Trek Farley 9.8, which is a spitting image of the Fatboy (same design cues and all) and, though a touch heavier, costs a couple grand less. The Salsa Beargrease is another excellent option: again, it’s heavier and maybe not quite the epitome of what’s possible design-wise, but it’s also half the price and, with a slacker front end, a bit more playful and all-around oriented. There is no shortage of excellent niche companies that can keep up, including Fatback with its race-proven Corvus, 9:Zero:7 with the Whiteout, and several solid models from Borealis. The Specialized, however, is surely the epitome of the genre for those who demand the finest.

Buying Advice

(Jen Judge)

You will not find a better race bike than the S-Works Fatboy. It is astonishingly light, surprisingly nimble, and one hell of a conversation piece. Just as important, it’s an exemplar of the growth and development in the fat bike industry. Having said that, for most of the population (myself included), a $7,500 fat bike is not in the budget, even if it doubles as a summer hardtail. The good news is that the two lower-tier Fatboy models get the same awesome frame and are just as worthy of purchase—for between $2,900 and $4,600 less. At $5,400, the Fatboy Expert Carbon in particular is an incredible buy because it comes with the same HED wheels and only very slightly lower spec. In either case, you won’t get the whizbang tech and outrageously light weight—but you will get one hell of a fun ride when the white stuff starts piling up.

Lead Photo: Jen Judge

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