Swapping 27.5+ Wheels for 29ers
It's a Jekyll/Hyde thing. With plus sized tires, the 6Fattie is laidback, imprecise, smash-through-anything fun on the downhill. But it's also sluggish on the flats and smoother climbs. The 29er build feels faster and much more efficient, especially climbing up less technical terrain, but reduced traction takes away from the flat-out fun factor. We call it a style based tie.
We tested the 27.5+ version on the left in the spring of 2017 and the 29er on the right, in the fall. Two rode them both back to back in the summer. When it comes to choosing between the two versions, our testers, both aggressive descenders who like long rides, disagree. One prefers the original 27.5+ version, stating that much of the bike's personality disappears when rolling around on the 29er wheelset. To him, the 29er Stumpjumper's handling feels remarkably average. It's capable, but standard, cornering like a 29er and not coming close to touching the excellent traction of the aggressive feel of the Yeti SB5.5 or the poise of the Ibis Ripley. It's hard for him to love. In contrast, with the 3-inch tires, the 6Fattie version puts a smile on his face despite how much he hates climbing on the Ohlins rear shock with its lack of a lockout.
The other tester appreciated the reduced traction of the 29er, feeling like it's cornering is excellent, faster than the 6Fattie. The lighter tires are also easier for him to throw around. He sees it as a playful and efficient rocketship, charging efficiently, descending confidently and launching jumps.
The Stumpjumer is also available in a women's version called the Rhyme. The female version is available in 27/27.5+ only. There is no 29-inch option. The Rhyme shares the same frame as the Stumpjumper but has a lighter shock tune, shorter cranks, and female-friendly contact points.
6Fattie Analysis and Test Results
We don't appreciate the Stumpjumper 6Fattie for a long day of grinding uphill, but it's game for pretty much anything else. When you get it over the hump and head downhill it just spills over the edge, like an avalanche, a really, really fun one. A blast on the descents and good for glossing over tech on the climbs, it'll slow you down on the flat and mellow hardpack. As long as you aren't racing or trying to keep up with your quad-zilla buddies, you won't be bummed about this bike. That being said, none of us would want it for our only ride.
Floating in the air and catching you like a cloud on the landing all we have to say about popping the Stumpjumper 6Fattie off the lip is "wheeee!"
We have one question: Why didn't someone figure this out sooner? Everyone agreed that bouncing downhill on 3-inch of tire is an insanely fun way to spend a day. One tester climbed off the bike raving: "This is this my favorite test bike to ride downhill, ever!" In the same breath, he wondered if plus bikes were just a fad. But we say when a bike is this fun today, who cares about tomorrow?
The Stumpjumper is a riot, so fun it made our faces hurt. You have the confidence to roll into anything, knowing you'll come right back out, allowing you to approach abrupt technical transitions with reckless abandon. The margin for error is enormous. This bike's got your back. The 6Fattie lends itself to unorthodox adventures, like night rides, when you don't want to have to work hard just to stay upright. As long as you have the strength to pedal it is going to charge. This bike even makes rocky uphill singletrack fun, because it makes it easy.
The Stumpie is also fun to jump. You'll want to hit every side jump, lobbing through the air so slowly and caught by the tires so gently that you won't be certain you ever left the ground. "What just happened?" It will give you a lot of pop if you load the tires, or just let you bounce house around.
It does, however, sanitize the trail, and nothing is more murderous to the great outdoors than the nose withering stench of bleach. On smooth singletrack, you're just dragging those massive tires around, not having such a good time. You'll enjoy it more if you primarily ride down more technical terrain.
The suspension and tire combo keeps the bike feeling smooth on the descents but can suck up pedal power on the flats.
It takes a minute to get used to most bikes. When you jump on the Stumpjumper 6Fattie for the first time, it feels like you've been riding it your whole life. It's stable, smooth, predictable and forgiving, tracking nicely through chunky sections. But its vague feel isn't for everyone.
In the way that driving a monster truck in rush hour traffic makes you feel pretty confident that you'll get to your destination on time, the Stumpjumper 6Fattie guarantees that you'll make it down the trail just fine. It feels secure. Never threatening to pinball through the rocky stuff. The 6Fattie has technical skills all its own. You have to struggle to do anything wrong on this bike.
If you do blow a line, you can choose to recover or just let it ride. If there is a bike to step up your game by trying that bigger, burlier line, this is it. The handling is fairly responsive for our bigger riders, if on the slow side. One of our 5'7", 140lb testers had a tough time wrangling the 6Fattie around. Luckily, its tires more or less eliminate the need for bike handling skills. It's almost less effective to pick a line than to just bulldoze through. This bike widens trails.
It's easy to get where you need to go with a cockpit this comfortable.
The 6Fattie sets you up in a very neutral position, centered over the cranks, and it wants you to stay there. It starts to lose it if you move too far forward or back. There's not that much to do, and it's hard to change this bike's laid-back mood. Only our most aggressive rider considered it playful on the descents. When you're moving slowly, it can feel pretty clunky and sluggish.
This bothered some of our test riders more than others. A big part of what these pros like about mountain biking is using the precise handling skills they've spent years perfecting. The Stumpjumper 6Fattie doesn't require all that hard mental work and physical finesse. Since it will roll over your line choice anyway, it often doesn't seem worth the effort. One tester found the outside of his forearm worked from wrenching around the handlebars after a long descent on this bike.
The Stumpjumper simply erases the more jarring aspects of mountain biking. Ghostly quiet and incredibly plush, the 6Fattie's suspension, added by those 3-inch tires, feels like it belongs on a downhill bike. The boosted 150mm RockShox Pike RC 29/27.5+ Solo Air fork feels excellent, though its action is hard to isolate from the cushy tires. On smoother tracks, it feels like we're in the middle of the travel the whole time.
The Custom Öhlins STX rear shock is an oddly complicated spec for a plus bike. The tire volume hides much of its function. And we can't discern a difference when adjusting compression and rebound settings on this shock. The autosag adjustment didn't work for our riders either. The shock always feels wide open, twist some dials, move the levers and… nothing. It's fine for the descents. Otherwise, it's just annoying. Still, the plus size tires maintain tons of traction and send small bump compliance soaring off the charts.
The Stumpjumper 6Fattie offers unstoppable confidence levels and backs it up at every turn.
One complication in the tire/suspension system is the undampened rebound you get out of the tires. There is just no way to control all that rubber. Sometimes they work together and sometimes they're fighting, and you're the one getting punched. Occasionally the tire just skips along the ground where the suspension should be keeping it in firm contact. They work together great on big hits but can get disheveled on smaller, consistent impacts. For that reason, it's super important to dial in the fork and rear shock rebound settings to reduce this effect to the extent possible. As we've mentioned, it's a difficult feat on the vague feeling Öhlins.
Still, the traction is superb. The only time we lose it is when we move around on the bike and unweight the tires. Out of the saddle climbing and poorly set up turns that make it hard to press the tires into the corner are the main culprits. Either of these situations can give you a momentary spin out. When the tires are on the ground they conform and grip, their pliability creates impressive traction. We'd like to ride this bike with a rear shock that offered some actual adjustability.
A blast on the descents, the Stumpjumper 6Fattie opens up your options on the trail with it's unflappable stability and forgiving tires.
The 6Fattie has good traction in the corners, as long as you are forcing weight evenly into the tires, but it feels slow. If you keep your weight on the rubber, it excels at slower speeds. It takes flat and loose corners cleanly and maintains traction where there would normally be none, feeling much more stable than any other bike in those situations. It's also fun in the berms where it's easy to press the tire into the wall.
Overall, the Stumpjumper 6Fattie is a vague feeling bike, and cornering is a precise skill. It suffers most from a slow and sloppy sensation and wresting it over gives your arms a real workout. As one would expect, it takes a while to traverse the three inches separating the "edges" of these tires, so you've got to be aggressive. While you have insane traction one minute because there is so much tire, when it slides out (which isn't often) it just goes, no warning.
The flip side is, for newbies not yet comfortable with laying a bike over to rely on those cornering knobs, the consistent traction around the tire feels more secure. If more experienced riders aren't riding for speed and can let go of expectations, it can be silly good fun. You can bounce it through the turns, pumping the tires and weight it in funky ways.
It's a stable bike with direct but slow steering.
Fine. The Specialized climbs just fine. Those fat tires make climbing up smooth or technical trails freakishly similar. Just give the 6Fattie some vague inclination of where to go and pedal. What's also universal is how much work that pedaling will be. The spinning pays off more on the technical trails than on the packed dirt tracks. Thus the fine. It's an average of awesome and awful.
The Stumpjumper is impressive when hauling its bulk over the rock juggernaut of our technical uphill climb. You trade out the snappy feel of the Ripley and the Mach 429 Trail for the Stumpie's vague tractor pull. As long as you can stay neutral and keep putting the power down, you're golden. Due to the monstrous tire volume, there are times when tire deflection can make the 6Fattie go haywire. Miss your mark when wheeling into a steep rock step and it kicks back. You'll find yourself spending heavily to rescue the bike. Other than that, you don't need many handling skills or mental input to clean technical lines.
It also corners well on the climbs, not giving us problems getting it around the stairstep switchbacks, which are surprisingly easy on this bike. Again this offends the hard-won skills of some of our testers.
It's harder to appreciate its performance on smooth trails. "I didn't know modern bikes could climb that bad," said one of our climbing testers after one mellow trail. "It's like trying to get a lazy boy up the hill." The bike has a lethargic pedaling feel, lugging those big wheels around comes at a cost. On the less technical climbs, there's the feeling of levitation. You're working hard to pedal up the hill, but the Specialized's suspension is just floating over everything. You don't feel a firm top or bottom. Between everything going on with the fork, shock, and tires you never really know whether you're in the travel or not.
It's a struggle to get the Stumpjumper 6Fattie up a hill, but it rock crawls way faster than we would have guessed.
As such, it's not the most efficient-feeling platform for pedaling. The Öhlins STX shock doesn't seem to have more than one setting, open. You can watch and feel your energy draining down into the fork stanchions and can run through half of the rear shock travel on smooth climbs. The tires suck up even more power. It's not energizing. When it's sandy and loose, you don't notice the slower pedaling as much, the float and grip of the 3-inch tires offset their weight, and their traction works in your favor. You notice it on good, tacky hardpack though, and the pedaling drags on the paved climb. What it lacks in acceleration it makes up for in steamroller smoothness and its lightweight feel.
The suspension can be borderline unacceptable when the rear shock sags far into its travel on a sudden steep uphill section, such as a slab. It drops the seat tube angle back too far like it's getting ready for liftoff, making it very hard to generate power. This leaves you feeling like you're pedaling your way out of the bike's back seat. If you could lock out or dampen the action of the rear shock compression when pedaling, we would be more excited to take this bike on smooth uphill rides.
Then there's that plus-sized tire bounce. Our flat pedaling tester noted that her feet bounce off the pedals on this bike, which isn't normally a problem for her and wasn't an issue for any of our other test bikes. She lost focus while repositioning. Traction was similarly affected. Tire grip is superb when seated and pedaling, but when you stand up to climb, or the tires otherwise bounce up off the ground, you can spin out.
On the technical climbs, the ever-open suspension works better. With the nonstop action responding to every impact and hinging the bike up the hill in a way that is shockingly effective without feeling like it. The front end takes care of business. It's very plush and predictable with a nice suspension curve.
Specialized's FSR is relatively straightforward to maintain.
Ease of Maintenance
It is important to examine such factors as ride characteristics, value, and build quality when deciding on a new bike. It is also important to factor in how much service is required to keep your new rig running smooth. Full suspension bikes have pivots and bearings that allow your front and rear triangles to move independently. Our ease of maintenance rankings relate to frame and suspension design, fork, rear shocks, brakes, and dropper posts. We explain our ranking methods in the main text of the trail review.
Specialized uses a proven suspension platform that is reliable and user-friendly. This design boasts long bearing life and when it comes to servicing your pivots, it is one of the easiest systems to work with. Öhlins recommends performing service more frequently than Fox but less often than RockShox. The RockShox fork has the most frequent service interval of any of our test bikes. SRAM brakes are harder to work on than Shimano and require corrosive fluid.
Here are the Stumpjumper 6Fattie's geometry numbers as measured by OutdoorGearLab. Check out our measurement methods over at How We Test.
Frame Design and Measurements
Specialized's Future Shock Rear (FSR) suspension is a version of the Horst Link or four-bar system. The design uses two pivots and a yoke between the seat stay and seat tube. Another pivot is just above the bottom bracket. The fourth is on the chainstay near the rear axle, separating the axle and wheel from the rest of the frame. The system has a reputation for reducing brake jack and reasonable small bump compliance but is often rough on larger hits. It also tends to rely on the rear shock to reduce pedal bob.
For the most part, the frame geometry worked well, the bottom bracket height (the second lowest in the test at 329mm) does force pedal strikes. You've gotta time your pedal strokes in the rocks. Several of us also had problems with our calves hitting the rear triangle as we moved back over the bike. At 29.05 lbs it's also pretty hefty. Since that weight detracted from our climbing experience on this bike, we count it as a negative. We didn't use the SWAT much during testing but love the utility and were pleasantly surprised by everything you could fit in there.
The fit is standard on the Specialized Stumpjumper 6Fattie. It's a very comfortable bike for all of our testers, setting them up in a neutral, upright position in a compact cockpit. Between that and the extra cushion provided by the tires, this bike is a really good bike for longevity. It's a luxurious ride, easy on your body, your wrists and back. It's like everyone's been driving cars and this is the first SUV.
The SWAT satisfies our desire to ditch the backpack.
Overall the build is fairly good, the components working together without complaining too much. The didn't appreciate aluminum bars and cranks at this price point and bemoaned the lack of pedal platform in the rear shock.
The Custom Öhlins STX offers a great downhill ride but won't slow it's action for the climbs.
Fork and Rear Shock — We like the boosted 150mm RockShox Pike RC 29/27.5+ Solo Air fork. The Custom Öhlins STX gave us a cushy ride on the descents but drove us crazy with its lack of anything approaching a trail mode or lockout for the climbs. And that autosag feature is useless, just get on your bike and set it up the old-fashioned way.
The 3" Purgatory GRID up front provided a lot of traction, but we can feel it let loose a little when pedaling, braking or cornering. We'd prefer a Butcher GRID.
Wheels and Tires — The boosted Roval Traverse 650 wheels with 29mm rims wheels worked well. The hubs were a little slower to engage than we'd like.
While those 3-inch Purgatory GRID tires offer up traction in spades, we wanted even more. The knobs are spaced pretty far apart, which is apparent when pedaling, braking or cornering. The front tire isn't that awesome. It's not as grippy as we would like. We'd rather see a Butcher GRID on there. We also had trouble keeping air in the tires and sealant bled through the rear tire's sidewall. Meant to lighten the load of those tires, the wall is a thin one, and the tires finicky as a result.
Sealant bled through the walls of the rear tire.
Groupset — We like the SRAM X01 Eagle's crisp shifting and lazy-rider range of gears, but the chain freaked us out, especially when we were putting the hammer down in extreme gears. Due to of all the cross loading pressures it didn't seem like it would last that long. We were right. One of our testers busted it during testing. This also happened on the Pivot Mach 429 Trail and Yeti SB5.5, making us reconsider our Eagle affinity.
The SRAM Guide RS brakes work well enough, but we prefer the extra adjustability of the RSC's, and some of our testers found them a little squishy after the Pivot's benchmark Shimano Deore XT stoppers. We also could have used a 180mm rotor in the rear to power them up a bit. Tires this wide should be able to utilize more of the power that modern brakes provide.
We'd like a wider, carbon handlebar on this bike.
Handlebars, Seat, and Seatpost — The 750mm alloy Specialized Trail 7050 handlebars are a bit narrow, and aluminum. We didn't need the vibration dampening that carbon supplies since the tires didn't take any hits hard enough to transfer up the frame. Still, we would have liked carbon for the price. The 750mm bars worked well enough for handling and were great when squeezing through the rocks.
It works, but the Command Post IRcc is frighteningly fast and can't compare to the RockShox Reverb or Race Face Turbine.
The saddle is fine, but the Command Post IRcc dropper was not the best. It's overactive, coming up at you scary fast. We prefer the RockShox Reverb.
Not necessarily a bike for your longest days in the saddle, the Stumpjumper 6Fattie has enough of a sense of humor to keep you smiling on a wide range of terrain.
The Stumpjumper 6Fattie comes in at $6,500 which is a pretty fair price for a respectably built carbon bike, but its lack of versatility keeps it from being a very good bike. This isn't the best choice for most riders' only bike, and it's pricey for a very specific addition to a quiver.
Switch Out Standoff — Specialized Stumpjumper versus Pivot Mach 429 Trail
The Pivot Mach 429 Trail
feels both more efficient and trail oriented than the Stumpjumper
in both their guises, 29 and 27.5+. While the 3-inch tires on the Stumpjumper 6Fattie
are fun, we think the 2.8-inch rubber on the Mach 429 Trail
is the plus size sweet spot. They don't have as much uncontrollable bounce and are lighter, making cornering easier. You can take better advantage of all that traction because you can still move the bike around. They also work with a wider psi range, making the bike more adjustable. The 3-inch tires on the Stumpjumper
are a little too forgiving, verging on gimmicky.
Ultimately the Pivot Mach 429 Trail is the better switch bike, acting like a legitimate XC racer in its 29er form and smashing trails so hard and efficiently as a 27.5+ it could go enduro.
It'll get you around with an imprecise feeling that is confidence building for beginners but too vague for the tastes of our experienced crew.
The Stumpjumper 6Fattie
makes us feel like suburbanites from the '50's. We're not sure what to make of it because it doesn't fit into any of our boxes. Most of us would never have considered buying one. Then we rode it. Now we're considering it as a special uses addition to the quiver. It's hard to recommend the 6Fattie
as anyone's only bike. It's a lot of bike to push around, and it's not in a hurry to get anywhere. We can't deny that riding it has a way of wearing you out. Still, the Stumpjumper
is an awesome ride to calibrate your confidence — from a beginner looking for some positive singletrack experiences to an intermediate or expert taking on new terrain. That means dumbing down a lot of technical aspects of the trail, which can be the fun part for experienced riders. As one tester puts it, "it's good for drunk mountain biking, or as a rental." Having ready access to one would always be a plus.