With the 2021 Specialized Stumpjumper Expert, the original - and arguably the world's most popular - trail bike gets a hosts of refinements.
The 2021 Specialized Stumpjumper Expert boasts new sizing and geometry and a focus on lightweight minimalism.
2021 Specialized Stumpjumper need to know
- The latest iteration of the iconic Stumpjumper gets a focus on light weight and improved frame sizing
- No more 27.5in wheels
- Carbon and alloy frames, with the range starting at £1,900 and topping out at £8,750 for the S-Works model
- By ditching the the Stumpjumper ST (Short Travel) the new Stumpjumper takes a slightly more XC approach and moves further away from the Evo
- No more Horst link on the chainstay, instead the whole swingarm is engineered to flex
- Six frame sizes accommodate a broad range of human dimensions
It might be considered the Ford Mondeo of mountain biking, but there’s no shortage of Vorsprung durch Technik with new Specialized Stumpjumper. Lighter, longer and more likeable than the 2019 Specialized Stumpjumper, Specialized’s engineers have taken a reductionist approach with the end goal of creating an even more rewarding ride. Fewer wheel sizes, fewer pivots and less material means the 2021 Stumpjumper is leaner and keener, but a massive range of six frame sizes ensures it fits even more riders than ever before.
A bit more Epic, a lot less Stumpy
You’ll hear a lot about weight saving with the new Stumpjumper, perhaps as a reaction to average trail bike weights breaching 30lbs on a regular basis now, and perhaps to keep the Stumpjumper more relevant compared to the lightweight ebike option Specialized Turbo Levo SL. Either way, the new Stumpjumper frame is, according to Specialized, over 100g lighter than the old model, while the top end frame with shock and hardware in size S4 is a claimed 2,420g (alloy frame 3,490g). That’s right up there with other minimal trail bikes such as the Scott Genius Tuned (2,249g) and Transition’s Spur (2,450g).
Slightly disappointing then, that our complete Expert S4 test bike weighed 13.63kg, or just over the 30lb threshold, although it’s still nearly 500g lighter than the Expert Carbon 29 we tested last year. A chunk of change (55g according to Spesh) has been lost by getting rid of Specialized’s signature Horst link – a move that might seem blasphemous to most aficionados, but makes absolute sense when combined with the new Stumpy’s reduced travel.
With 130mm – 10mm less than previously – out back, any variation in angle at the swinglink and main pivot can be accounted for by the engineered flex stays. It’s a trick that many short travel trail bikes have used to save weight and simplify production, including the Specialized Epic Evo and Epic XC bikes. So weight has gone down, but frame lengths have gone up, and the new Stumpjumper gets the ‘S’ size designation introduced on the Stumpy Evo and adopted by the Specialized Enduro and Specialized Turbo Kenevo. Now you can choose between six different frame sizes, and, more importantly, there’s a lot more bandwidth to go up or down a frame size according to how and where you ride.
Long reach, short seat tubes
Our principle complaint with the previous Stumpjumper was the sizing. Short chainstays combined with a short reach made for a lack of stability at higher speeds and a difficult balancing act when trying to centre your weight between the contact patches. And because the head tube was dizzyingly tall and the seat tube both long and slack, you couldn’t easily upsize to the next frame. Thankfully all that has changed on the new Stumpjumper, and if we’re being honest, this is the single most significant update to the whole bike as it will transform how many riders it will fit and how hard you can ride it.
In terms of reach, the scale goes from 410mm on the S1 to 530mm on the S6, with the S4 that we rode measuring 485mm (475mm claimed). Not only is that 40mm(!!) longer than the old size large Stumpy, the new bike gets a shorter head tube (-5mm) and seat tube (-30mm), which makes it possible to upsize from an old Medium to a new S4. And it’s the same throughout the range – there’s so much more flexibility when choosing frame size. In an instant Specialized has gone from zero to hero on the sizing front.
Proportional chainstay lengths
While the bread and butter Stumpjumper doesn’t get the adjustable chainstay chips found on the Evo, it still gets proportional rear centre lengths to keep the handling balanced between frame sizes. S1 to S4 frames get 432mm chainstays, extending to 442mm on the S5 and S6. It’s a new move for Specialized, following in the footsteps of brands such as Santa Cruz, Mondraker and YT in aiming to keep the ride experience consistent whatever your height. There’s also a move to short offset forks, which will add steering stability and keep the wheelbase length in check.
The proportional chainstay lengths also represent a development of the Rider-First engineering focus that inspired the Sidearm frame design. This was introduced after Specialized found that the larger frame sizes were flexing more under extreme shock loads than the smaller sizes. The Sidearm was added to structurally tie the forward shock mount to the swing-link, significantly boosting the stiffness under compression forces from the shock. The latest version of the Sidearm has been tweaked too, attaching to a straighter top tube that retains greater structural integrity.
As is always the case, Specialized’s in-house boffins have custom-tuned the shocks in concert with the kinematics to create their desired response. Zero surprises here, that what they were seeking was efficient pedalling performance with mid-stroke support, excellent bump compliance and enough progression to resist harsh bottom outs. Like everyone else then. And if you’re looking for graphs and charts there are plenty of those to back up its claims. But the proof of the pudding is in the riding, and we’ll get to that in a moment.
Specialized has retained its clever offset hardware in the shock yoke to give you some control over adjusting frame geometry. It’s not as involved as the Stumpy Evo system, but it’s quick to switch and simple to understand. There’s now a revised graphic on the yoke explaining which way is which, and the gizmo itself allows for a 7mm change in BB height and a 0.5º change in head angle.
Stumpjumper Expert spec
Our Stumpjumper Expert test bike sits mid-range among the carbon frame models and comes in at £4,750 in the UK (we’ve amended this price following a correction from Specialized UK). It gets a FACT 11m carbon frame with integrated SWAT down tube storage. There’s a Fox Float DPS Performance Elite shock with Specialized’s RX Trail Tune and EVOL air can. To firm the compression damping, you have a three-position lever that’s within easy reach under the top tube. Up front there’s Fox’s Float 34 Performance Elite suspension fork with Grip 2 damper and 44mm fork offset. With only 140mm of travel, Specialized has obviously decided to pocket the weight savings of the more slender fork over any stiffness gained by moving to a 36.
However, there are burlier four-piston SRAM Guide G2 RSC disc brakes with a 200mm rotor up front and reinforced casing Butcher/Purgatory Grid/Gripton tyres wrapped around Roval Traverse 30mm rims. The S4 frame size we rode had 170mm cranks, a 55mm stem and a 170mm X-Fusion Manic dropper post.
How it rides
We rode the new Stumpjumper in Scotland’s Tweed Valley mecca, on an old-school trail loop with a big climb and big descent followed by shorter laps of some hand-cut rooty singletrack. In total we only did around 27km and 1,100m of climbing on the bike, so we can’t consider this a definitive review, but here’s what we found.
The good news is that Specialized has made huge strides forward with the 2021 Stumpjumper sizing and geometry. The size S4 that we rode needed minimal adjustment to get a comfortable riding position – no need to slam the stem like the old Stumpjumper and no constant voice in the back of my head saying ‘this thing is tiny’. That extra reach drops it bang into contemporary trail bike territory; a Goldilocks just-right length that doesn’t ruffle any feathers but gets it back in the game. And thanks to those truncated head and seat tubes, at 5ft 10in I could easily step up to a S5 frame and still run a 170mm dropper post. While I didn’t get enough time to make that leap at the launch, it’s something I would like to try in conjunction with a shorter stem (55mm is on the long side for my liking).
So the new Stumpjumper puts you in an excellent riding position, both standing and seated, thanks to a steeper seat tube angle. But take that first pedal stroke and something feels amiss. There’s a mushy, spongy response to the first stab of pedal input that leaves your heart sinking at the same rate as the suspension. And this continues most of the way up the first climb – made worse by my pedals taking chunks of peat out of the rutted climb – until I can take no more and flick the climb switch to the right on the DPS shock. Fortunately this makes all the difference, helping the Stumpjumper to drive forwards rather than squat and sink. As a solution it’s perfectly acceptable, but it does mean that you’ve either got to compromise on bump performance by adding damping all the time, or remember to regularly switch it on and off.
With hindsight, the smart option would have been to also put the shock link in the steep/high setting for the climb, which would have raised the BB and given more pedal clearance on the lumpy, rutted climbs.
Surrounded by a sprawling view of the Pentland hills and a long descent extending ahead, it was hard not to be excited by the time we reached the top of the climb. And a classic old school descent it was, with high speeds, loose rock, marginal grip and the trepidation that comes with never quite knowing what’s coming next. And while the Stumpjumper was competent, it never quite blew me away either. Maybe I’ve just got used to forks with big upper tubes, but on the fastest straights there was a slight sense of vagueness from the front end. Perhaps the long stem didn’t help here either. At the back, the suspension only started to come alive on the chunkier sections, where it felt fluid and effective. But it never felt lively or poppy like its Evo sibling when weighting and unweighting for grip or getting the bike airborne.
As a track and trace system, it felt far from world beating, whereas something like the Nukeproof Reactor brings a far more exciting, inspiring performance that mixes grip, support and efficiency on a wide variety of terrain. Whether it’s the added spring force of the flex-stay rear end, or the light shock tune, or the anti-squat values, or a combination of everything that’s spoiling the party, I’m not sure, but from the seat of my pants, the new Stumpjumper felt more like an appliance than a plaything.
As it stands then, after this brief introduction I’m slightly underwhelmed. Maybe it’s because in my mind the Stumpy sits in the shadow of its Evo sibling, or maybe I just need more time on the bike, but while the 2021 Sumpjumper is a big step forwards in sizing and geo, it’s a bit underwhelming in the wild.