2021 Specialized S-Works Stumpjumper Review: An Efficient and Lightweight Trail Bike

Check out the 2021 Singletracks Mid-Travel Mashup reviews on Singletracks and video reviews on our YouTube channel.

Some weight and responsibility accompanies a bike review like this one, especially with a model as beloved as the classic Specialized Stumpjumper. There are riders out there who have owned every iteration of this bike, and likely a few who have a spare garage bay full of them. Alas, my job is to negate the fanfare and answer the question of “who and what is this bike best suited for?”

This latest Stumpjumper takes shape around a pair of 29″ wheels, with a 130mm rear axle path gliding through one main pivot and a pair of flexing seat stays, all led by a 140mm Fox 34 fork. Those flexy stays drop weight and complexity while providing a clear demarcation line between it and the longer-legged Stumpjumper EVO with its Horst-link 150mm of travel and 160mm fork.

This shorter-travel Stumpjumper is available in five sizes, with four builds centered around the carbon frame ranging from $4,700 to $10,500, and two 130mm Horst-link alloy builds that retail for $2,500 and $3,500. Carbon S-Works frame sets are available à la carte for $3,000 with a Fox Float DPX2 Factory shock.

Test pilot profile height: 5’9″ (175cm) weight: 145lbs. (65kg) testing zone: Northern Italy

Frame features and geo

This sleek black frame is covered in well-considered details that make the overall package quite appealing. Up front, the guided cable and hose routing tucks in at the face of the head tube to eliminate paint scratches and trail rattle. Clean and quiet is the name of the game all the way through this frame, and the cables exit their snaked carbon homes just briefly above the bottom bracket before dipping back inside to reach their final destinations. Their brief appearance at the BB keeps them tucked away from the chainring, and out of the huck-line of sticks and stones.

A relatively straight seat tube allows the RockShox Reverb AXS dropper to be slid all the way to its collar, which should make space for some shorter-legged riders to select frames with longer reach measurements if they like. While I didn’t mount a cable-actuated dropper on this bike, it looks to be as simple as sliding one tube through another, like the rest of the routing. Given the size S3 frame’s shorter seat tube, I might be tempted to sell the AXS dropper and replace it with a 170mm model for a little additional party space.

It’s great to see more frame designers adding chain-slap silencing material the to inner edge seat stays. Overall, the silencing system on this bike works really well with the SRAM derailleur clutch to let you listen to the birds and the traction. None of the pivots creaked through the review period, despite several muddy rides and subsequent washes, and the Stumpjumper seems the right ride for folks who like a silent bike.

Mud clearance is ample around the supplied Specialized 29 x 2.3″ Purgatory tire, and there is definitely space for wider rubber. The vulnerable space between triangles, just ahead fo the main pivot, seems ripe for the sort of crud collecting that sands frames and can make heaps of noise. As with many frames, a hunk of moto-foam between the two triangles will be a worthwhile preventative measure.

The horizontal hands-to-feet measurement (reach) for this S3 size frame is 450mm in the low position, and 455mm in high. That same shock-mounted flip chip leans the head tube between two festive settings of 65° and 65.5°. The frame’s vertical hands-to-feet measurement (stack) is a somewhat short 622mm in low, and fortunately the fork was cut long enough to slide a pile of spacers under the stem. Chainstay lengths are a consistently short 332mm on S1-S4 sizes, reaching to 442mm to better balance the S5 and S6 front triangles. The feet-to-ground measurement (BB height) is a squatty 340mm on all but the S1 size that has a 335mm BB height, and the seat tube perched above leans to 76° across the size run in low.

I received the Stumpjumper with the chip in the low position and kept it there to best suit our nearby trails.

Bulid spec considerations

Apart from folks with painful arthritis, who needs electronic shifting? I haven’t yet found a definitive answer to that question, but it’s cool to listen to cute little robots toiling away on your bike if you can afford to. The S-Works build comes with a full SRAM XX1 Eagle AXS 12-speed drivetrain and the equally-robotic wireless dropper post. These bits functioned flawlessly throughout the test period, as expected. The shifts are clean and precise under load, and the dropper works as automatically as a cable-actuated version—provided you remember to charge the battery.

A set of Roval carbon wheels and handlebars keep the weight low and the price high, all smoothed out by some Kashima-coated Fox bits front and rear. There are few places to save weight on this build, unless you want to really crank the price and find some tiny boutique brands that focus solely on gram savings. The stock Purgatory and Butcher tire combo could certainly be lighter, and folks who live in flatter places could swap the 4-piston SRAM G2 Ultimate brakes for a 2-piston set and exchange the 200mm front rotor for a smaller diameter. But when you’re pushing this bike toward its limits, those brakes and tires fit well with the Stumpjumper’s capabilities.

So, is all that S-Works bling worth the $10,500 tag? That depends on your paycheck, budget, and desire to have shiny bits that may not directly improve your ride experience. Downgrading to the base Stumpy Comp build will get you the same carbon frame with a complete build that’s priced just $1,700 more than the á la carte frameset’s retail number, and it would be tough to build up a frameset with fresh components for that price. Of course the less expensive build incurs a weight penalty, but at significantly less than half the price of the S-Works it might be worth upgrading the base model as things wear out to arrive at a similar weight. The alloy models cut the price further, but given their different suspension platform they are also going to offer their own flavor of jumping stumps.

Pedaling platform

The compression switch stayed in the middle most of the time.

This bike is a pleasure to pedal up mid-grade mountains. With the shock pumped up for proper descending support, I was able to leave the three-position lever in the middle on most rides. Even during asphalt climbs the rear suspension remains stable and bobs little enough that there’s no need to fully lock the shock out. When the compression switch is fully closed the Stumpjumper essentially becomes a hardtail, with a super efficient rear end to sprint against. There’s still plenty of rear suspension movement to create grip on technical sections, and even more is available by opening that blue lever all the way.

The 76° seat tube angle fits well with the bike’s average reach for a comfortable seated climbing position on mid-grade climbs of 10° or less. When the track tilts steeper the bike’s short 432mm chain stays combine with that cozy seat tube angle to make it somewhat difficult to maintain front-tire grip and direction. I frequently find myself perched on the nose of the saddle like a classic XC bike in order to plant the front tire and point the bike where I want it to go. All of this could be remedied with a tad-steeper seat tube angle, and folks who enjoy steep climbs may want to try slamming the saddle all the way forward on this current frame. The bike comes with a 50mm stem and 780mm bars, and I wouldn’t want to lengthen the stem to get that front tire grip on climbs at the expense of compromised handling on the descent. I would, however, love to test this same front triangle with the longer 442mm chain stays to see how much of an influence that variable has on front tire grip.

A good amount of weight is saved right here, with no rear pivot hardware, and spacing for a 180mm rotor without an adaptor.

Without pedals, and with at least 100g of mud, the S-Works Stumpjumper in size S3 weighs a sliver under 12.25kg (27lbs). That makes it the lightest bike I’ve ridden in a few years, and those feathers make a significant difference in the way it performs. Compared to some of the burlier gravity sleds I’ve been testing it feels like climbing with a low-powered e-bike. The stiff frame allows you to spin up as much power as your legs can muster to rocket this thing to the top without any noticeable flex from the rear end.

I was curious if the flex-stays would make the bike feel overly rigid on climbs, but the shock tune plays well with that flexy fiber to create a smooth rolling climber all the way up. It’s lighter-weight and takes less effort to pedal up the trail than my personal 130mm-forked hardtail, which seems significant. Once you sort out the weight imbalance, this little machine will likely out-climb your previous bike, and it may even descend better.

Downhill dexterity

Reacquainting myself with a lightweight bike took a little time. All of this carbon bling not only goes up differently, it also comes off the ground without being asked, and requires its own form of focus on the way down hill. The average reach measurement allows the rider to keep most of their mass in their feet, with no stretched front end to lean into for front wheel traction.

The loftier front-end sensation experienced while climbing vanishes as soon as the ground points down, and the shorter chainstays make it easy to get the Stumpjumper up and over whatever trail feature you want to bunny hop or pop off. Those same brief chain stays and shorter overall wheelbase also keep the platform poised for tight turns on slower technical trails. This is a party of a 29er, bounding around the trail and swapping lines with notably little effort. With the rebound dialed right the bike snaps out of berms to compress the next, making it a blast on purpose-built singletrack. The rear end can become a little jittery on the bumpier flat and off-camber turns, but with a little coaxing and some extra lean it will come around.

Finding the gravity limits of this bike was a harder task than I had imagined, and once I did find them it was still fun to ride. I mounted up tires with sturdier casings for a few laps down the local “long travel” trails to see how it would handle, and was impressed by the amount of midstroke and bottom-out support the shock and stays provide. You can really push it through the rocks without the bike wallowing or hitting the end of its travel too frequently. You’ll know when it’s overwhelmed, as the trail smoothing properties fall off, but it takes some effort to get there. The shock does eventually heat up and stiffen on longer descents, as expected, which could likely be remedied with a heftier gravity shock—but I wouldn’t recommend it.

From the suspension to the tires and brakes, this bike is well equipped to be pushed as hard as its 130mm platform needs to be. If you’re looking for more than the Stumpjumper has to offer, you can go for the EVO model. Folks race enduro on that bike, working a lot harder to reach its limits. This model, instead, wants do everything really well, and what it sacrifices in the descent department is replaced by its broader range of capabilities. So much of the bike’s character comes from its feathery frame and build, and It’s arguably not one to swap in hefty components with. It’s just right out of the box.

What does a SWAT Box have to do with descending? Well, where do you most often flat, crash, and experience mechanicals? Most of my mishaps happen on the way down hill, and I love having everything I need on the bike at all times. With a tube, tire lever, emergency gel, and a pump in the down tube, and a SWAT multitool in the steerer, there is little that can’t be repaired alongside the trail. While the massive hole in the down tube no doubt creates a difficult engineering riddle, I would love to see more frame manufacturers considering storage like this inside those cavernous tubes.

Summing up the S-Works Stumpy

If a 130/140mm bike is the right fit for your local trails, this current Stumpjumper might be the right fit for you. Its low weight makes it a fun platform for long pedals, and it’s a worthwhile companion on most alpine descents. If the electronics and Kashima on this frame don’t do it for you there are some other solid build options with much lower price tags, all built around the same carbon triangles. If you have the budget to own two bikes, this could be a good companion for something longer travel like the Specialized Enduro, or paired with a hardtail if your preferred trails are more mellow.

Party laps

  • Notably efficient and lightweight climber
  • Internal frame storage is clean and convenient
  • Suspension is quite active, with ample mid-stroke support
  • More capable descender than some other 130mm platforms

Pros and the cons of the Specialized Stumpjumper.

Dirt naps

  • Steep climbing can get tricky
  • Pivot gap could use some moto-foam
  • Can’t fit a whole pizza in the SWAT box

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