Bike Test: Specialized Stumpjumper FSR Comp Carbon 6Fattie

The Stumpjumper name is synonymous with mountain biking. One could even say that the original Stumpy was the first real mountain bike to come off production lines way back in 1981. This newest iteration of the bike, the Stumpjumper 6Fattie, seeks to take the success of previous Stumpys and add some big, fat, fun wheels to the mix.


The Stumpjumper 6Fattie is built for traction, stability and, surprisingly, speed on the trail. The big tires inspire confidence through rough sections and are made to make even the loosest trails feel like hero dirt. Sure, it’s not a super-light cross-country weapon, nor is it a downhill suspension junkie’s sled; instead, it’s a 5-inch-travel trailbike that’s meant to provide confidence in trail conditions that would make lesser bikes quiver.


The Stumpy 6Fattie is built from a combination of carbon, aluminum and a whole lot of rubber. The front triangle is built using Specialized’s FACT carbon fiber, and the rear end is built using Specialized’s highest-end M5 aluminum alloy. The bike uses the patented FSR suspension design, which rides entirely on cartridge bearings. The bike also comes with all the modern amenities for plus-sized bikes, including 135 millimeters of travel, 148-millimeter rear dropout spacing, a PressFit 30 bottom bracket, tapered head tube, and Specialized’s patented Fox Float Autosag shock to make setup easier.

Carbon construction with nice value: The Expert version of the bike uses some hose-branded components to keep the price tag out of the stratosphere. However, the bike still retains the carbon front triangle that can be found on the more expensive versions of the bike.


Specialized uses a smart mix of Shimano and SRAM components to keep the performance as high as the value with this build. The SRAM GX drivetrain, although not as lightweight, provides essentially the same feel as the higher-end X01 and XX1 drivetrains without the high cost. The Shimano Deore brakes provided plenty of stopping power throughout our test and would be welcome on any of our test bikes.

Short and true: Specialized prefers to keep their chainstays short to keep the handling feeling quick and nimble. The Stumpy keeps them as short as possible, but the big tires have to fit somewhere.

Specialized has done its research when it comes to plus-sized tires. The Purgatory and Ground Control combo on this bike is relatively light and hides the plus size as well as can be expected. The tires feel relatively light and snappy and also have a supple carcass that conforms to the ground easily, further improving traction.

Impressive traction: The pre-ride opinions of a full-suspension, plus-sized bike were mixed from our test riders. Some thought they were in for a heavy and clunky ride. After a few laid-over fast corners enjoying the ample traction, those who weren’t on board quickly changed their minds.


Setting sag: This is the easiest part of setting up any Specialized that’s equipped with Autosag; the shock literally sets itself up. All you do is pump the shock’s main air spring way past what you actually need, then sit on the bike and hit the release valve. The shock releases pressure to put you at a perfect 25-per- cent sag. Don’t worry if your riding style or terrain requires something different, because you can always make adjustments after- ward. We matched the fork’s sag to 25 percent and hit the trails.

Classic and proven: The Stumpjumper 6Fattie uses Specialized’s FSR linkage that’s been a wrecking crew favorite for years. It provides very active small-bump compliance that is already great thanks to the big tire volume.

Moving out: The Stumpy’s carbon frame is fairly low-slung and provides plenty of standover. The top tube is on the long side and is designed to be run with a shortish stem. Our large-sized bike easily fit our 6-foot-plus-tall test riders without any modifications. The bike also features a fairly short rear end, considering the big wheels and big tires, which puts the rider in an aggressive but still comfortable position that’s perfect for trail riders.

Climbing: On short and technical “burst” climbs, this bike will claw its way up anything. Be sure your tire pressure is set low, and the traction will send you up the steepest of ascents. Our test riders noted that they cleaned sections they’ve never made before on this bike. This is one of the strongest attributes of the Stumpy 6Fattie.

On longer fire-road or paved climbs, you can expect to feel the weight of the big tires, that’s for sure. The Stumpy 6Fattie isn’t a heavy bike, but it carries the bulk of its weight on the outside of the rims, which makes it difficult to accelerate quickly. That said, however, the shock provides a nice platform to pedal on when set to the firmest setting. The Stumpy 6Fattie won’t be the first to the top of the hill, but it will get there with enough gumption.

Cornering: In the same way that real estate is all about location, location, location, cornering on a mountain bike is all about traction, traction, traction. The Stumpjumper 6Fattie takes the massive footprint of the plus-sized tires and combines it with an active suspension design that’s supple over small bumps. The result is a bike that almost corners too well. The Stumpy 6Fattie will follow you into any corner without hesitation, and the big tires will bite into even the loosest dirt like a fat guy into a Twinkie. We never found a corner that this bike couldn’t handle, and it improved the confidence of nearly every rider coming into turns he or she would typically deem “sketchy.” The bike did oversteer a few times, especially when the tire pressure was set a little too low. There is such a thing as too much traction, and this bike is truly capable of delivering it.

Descending: The Stumpy has long been a confident descender thanks to more than 5 inches of travel and a confidence-inspiring geometry. This new version offers two features that improve the descending prowess. First, the big tires offer tons of traction, allowing riders to shred high-speed sections without fear of sliding out and also to creep down steep chutes knowing that braking efforts will be rewarded with real stopping power. Rather than feeling like you’re on a rock-strewn Slip ’N’ Slide, you feel truly connected to the trails.

And second, the designers kicked the head angle out slightly to provide a slacker and lower feel. Whereas some plus-sized bikes can make you feel as if you’re riding on top of them, the Stumpy makes you feel as if you are “in the bike,” and thus more connected to the trail.

Supple feel: Combining over 5 inches of travel with these huge tires makes for a bike that’s supremely supple. The big tires take the high-frequency small bumps nearly out of the equation, and the real travel kicks in when the trail gets a little rowdy.

Impressive traction: The pre-ride opinions of a full-suspension, plus-sized bike were mixed from our test riders. Some thought they were in for a heavy and clunky ride. After a few laid-over fast corners enjoying the ample traction, those who weren’t on board quickly changed their minds.

Our only issue was when the tires surprised us with too much traction and oversteered us off the trail. This style of trailbike will require a bit of a learning curve, but with some practice, our riders felt the Stumpy could be faster on certain trails, especially those that are “blown out” and loose.

Nice combo: The FSR pivot, pictured here, keeps the suspension active under hard braking efforts, which improves the traction, even on loose or steep terrain.

Braking: The brakes are incredible, especially considering they’re mid-tier in Shimano’s line. The FSR design does a nice job keeping the rear suspension active under braking efforts, and the big tires allow the bike to track the trail with ease. Go ahead; jack the brakes. The Stumpy 6Fattie won’t complain.


The Specialized SWAT system is a novel idea. The bike comes equipped with a special door in the downtube that covers a storage space for spares and other things. The system is well-engineered, with a nice feel that’s easy to operate. If you use the compartment, be sure to wrap the contents in something soft to prevent rattling. Otherwise, it seems like a good idea, especially for those who prefer to ride without a pack.

Call the SWAT: Specialized’s SWAT (Storage, Water And Tools) system includes a hidden compartment on the downtube. The space is enough to fit a spare tube, a multi-tool and some small spare parts. It’s a gimmick to some, but is a great solution for those who prefer to ride without a pack.


A full-suspension, plus-sized bike may not have been the first purchase in the quiver for most riders just a year ago. Now, however, advancements in tire, wheel and suspension technology have made this bike a real contender for many, especially those who frequently ride trails that are loose and soft. The bike brings Specialized’s proven FSR feel to the plus-sized world and provides a little more cushion and traction when pushing the envelope on the trail. It also comes with a relatively lightweight package that has geometry to match the needs of real trail riders. It may not be the first choice for many riders, but on the right terrain, this is the right tool for the job.


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