Specialized’s 2021 Stumpjumper boasts a host of changes over the outgoing model including a refined look, new geometry and updated specs and sizing. Although it’s only available with 29in wheels, there are aluminium and carbon models.
- 2021 Specialized Stumpjumper loses Horst-link FSR pivot in favour of flexstay
- Specialized’s 2021 Stumpjumper Evo promises tantalising trail-domination
I tested the 2021 Stumpjumper Expert – that sits in the middle of the Stumpy range – at the bike’s UK launch in Scotland’s Tweed Valley, to find out whether the updated version builds on the outgoing model’s success and popularity.
2021 Specialized Stumpjumper Expert frame and suspension details
Built using Specialized’s FACT 11M carbon fibre front and rear triangles, the 130mm travel Stumpjumper features the – now synonymous with Specialized – asymmetrical Sidearm strut design, spanning the length of the rear shock from the top tube to seat tube.
Specialized claims this allows it to tune the frame to be as light as possible while delivering the desired levels of performance.
Along with the visually iconic Sidearm, Specialized’s latest Stumpjumper also has an onboard SWAT storage system. Supplied with the bike is a bag to carry tools or valuables, and there’s an external bottle cage that functions as the SWAT’s door, too.
Like the 2021 Stumpjumper Evo, the standard Stumpy has the same “Rider-First Engineered” approach to the bike’s feel and, in theory, a 50kg rider on the smallest Stumpjumper should experience the same ‘ride feel’ as a 120kg rider on the largest bike.
Most notably, the 2021 carbon fibre Stumpjumpers forego a Horst-link pivot on the rear suspension – synonymous with Speclaized’s FSR bikes – in favour of a flexstay, where the seatstay has in-built flex to mimic the job of a traditional pivot.
Specialized also says it’s designed the suspension to be progressive – roughly 19 per cent – to provide small bump sensitivity, mid-stroke support and ramp-up as well as bottom-out resistance.
Elsewhere, there are internally-routed cables from front to back with internal cable guides, integrated chain slap and down tube protection, and Boost rear axle spacing.
2021 Specialized Stumpjumper Expert geometry
The 2021 Stumpjumper, like its more extreme sibling, is available in six sizes, from S1 through to S6. I tested the S4 model that’s equivalent to a traditional size large. The geometry is adjustable between a high and low setting thanks to a flip-chip on the clevis linkage.
|High / low||S1||S2||S3||S4||S5||S6|
|Stack (mm)||610 / 614||609 / 613||618 / 622||627 / 632||636 / 641||646 / 650|
|Reach (mm)||415 / 410||435 / 430||455 / 450||480 / 475||505 / 500||535 / 530|
|Head tube angle (degrees)||65.5 / 65||65.5 / 65||65.5 / 65||65.5 / 65||65.5 / 65||65.5 / 65|
|Bottom bracket height (mm)||335 / 238||340 / 333||340 / 333||340 / 333||340 / 333||340 / 333|
|Front centre (mm)||724||746||770||800||829||836|
|Chainstay length (mm)||432||432||432||432||442||442|
|Top tube length (mm)||563||583||605||632||660||692|
|Standover height (mm)||730||734||744||749||757||757|
|Seat tube length (mm)||385||385||405||425||445||465|
|Seat tube angle (degrees)||76.5 / 76||76.5 / 76||76.5 / 76||76.5 / 76||76.5 / 76||76.5 / 76|
Standout figures on my S4 bike in the low setting include a 475mm reach, 65-degree head-tube angle and 76-degree seat-tube angle. It has a 1,228mm wheelbase and 432mm chainstays.
The standover height and seat-tube lengths measure 749mm and 425mm respectively, while bottom bracket height is 333mm.
The new Stumpy is 29in wheel only, and both the alloy and carbon versions share the same geometry.
2021 Specialized Stumpjumper Expert specifications
Sitting two models down from the top, the Stumpy Expert costs £4,750, hoping to strike a balance between performance and cost.
It’s kitted out with a host of top-performing parts including Fox’s Performance Elite 34 fork with GRIP2 damper and Float DPS Performance Elite rear shock.
It’s got a SRAM X01/GX Eagle 12-speed drivetrain mix and SRAM G2 RSC four-piston brakes. Elsewhere, own-brand Specialized kit takes care of the bars and saddle, while there are Specialized’s Roval branded rims and hubs clad in a Butcher and Purgatory tyre combo.
It’s got a Deity stem and grips, and an X-Fusion Manic dropper post with 170mm of travel with an SRL LE remote lever.
The S4 Stumpjumper Expert without pedals weighs 12.61kg on my scales.
2021 Specialized Stumpjumper Expert first ride impressions
The brand-new Stumpjumper was launched in the Tweed Valley in Scotland. This meant I got to ride it on my local trails, letting me compare it to other bike’s I’ve ridden on those tracks. However, time was limited and I’ve only spent a single day on the new bike so far.
2021 Specialized Stumpjumper Expert climbing performance
The Fox DPS shock’s climbing or firm setting tune had a robust feel, which was just as well because the open setting had a fairly light compression tune.
Although the suspension kinematic is as progressive as the Stumpjumper Evo, the light compression tune in open mode meant pedal bob was pronounced on climbs when seated or standing, but especially at higher cadences or with choppy pedal strokes.
The medium setting of the DPS’s three positions struck a good balance between the near absolute lockout of the firm setting, and the grip, compliance and comfort focus of open mode. Except for outright descending, I kept the shock in medium for the majority of the testing period.
The Stumpy’s geometry, while a leap forwards compared to the outgoing model with it closing in on the Evo’s factory settings, feels perfect for a run-of-the-mill trail bike that’s just as capable on all-day bridleway and singletrack epics as it is tackling laps of your local purpose-built trail centre.
On the climbs this translates to a seat tube angle that could do with being steeper – I still had to angle my saddle nose down and push it forward in the rails to better centralise my hips over the bottom bracket. But it worked for 95 per cent of the terrain I rode at the launch.
Nitpicking at seat tube angles aside, for the average trail centre and flowy singletrack rider, Specialized has tuned the Stumpy’s geometry well.
Generally, climbing was effortless and comfortable, and even after a long day in the saddle I remained fresh; a sensation surely helped by the shock’s forgiving open mode and the bike’s geometry.
And even though the Expert model is two down from the top-spec S-Works, its 12.65kg weight (without pedals, S4) meant that it was spritely enough, responding well to sharp bursts of high-intensity pedalling – as long as the suspension was in the middle or closed setting.
2021 Specialized Stumpjumper Expert descending performance
The 2021 Stumpjumper’s geometry suggests it should come alive on the descents thanks to lengthy reach figures, generous wheelbase numbers and a not-to-be-scoffed-at 65-degree head tube angle.
But, as with its climbing, the Stumpjumper’s descending was pretty middle of the road, with its potential stunted for the most part by its fork.
Although the Fox 34 chassis has proven to be consistently underwhelming on most gnarlier trails – and even Specialized decided to fit a Fox 36 and RockShox Pike to the old Stumpy – thanks to the GRIP2 damper (that wasn’t previously available on the 34 chassis), the fork has had a new lease of life.
It is still possible to produce the twangy and flexy feelings normally associated with pushing a Fox 34 hard, and it would be good to have the option to fit a Pike or 36 to the standard Stumpjumper, but a significant number of people will have no problems with the 34’s performance and will find the fork well-suited to the rear end’s forgiving kinematics.
The Fox’s DPS compression tune and factory volume spacer installation meant the suspension was easy to push to the limits once the terrain got chunky, steep or speeds increased. But overall traction was relatively high and the point at which the suspension’s limits were exceeded was predictable.
It’s relatively easy to tune air-sprung suspension with more bottom out tokens, and because Specialized has designed the Stumpy’s spring rate to be “right in the middle of Fox’s volume spacer adjustment range” there’s plenty of scope to harden things up once the trails get spicy.
And just like on the climbs, the geometry is most at home on trail centres, bridleways and general trail bashing. Steeper, rougher or faster descents upset the bike’s composure and it did begin to feel twitchy.
However, those not looking to push the envelope of speed or tackle downhill tracks will revel in the intuitive and balanced nature of its descending performance at most trail centres. On the right terrain, I can guarantee they’ll have a great time on the Stumpy, just like I did.
Now that the standard Stumpjumper uses Specialized’s reach and style-specific sizing, it has a short seat-tube length and low standover height. This has its advantages, including shorter riders being able to ride larger bikes and reduced kicks from the bike’s seat on descents.
Unfortunately, the dropper posts Specialized has specced don’t have adequate travel to extend high enough for the climbs while dropping low enough to take full advantage of the short seat-tube length without requiring manual adjustment.
This is a relatively easy fix, but for a brand doing such a good job with sizing it would be good to see the rest of the spec follow suit.
Overall, the Stumpjumper’s Expert build felt good and performed well, blending performance with cost-saving well. I did think the Butcher and Purgatory tyre compound was a little hard, which limited grip over slippery, wet rocks and roots, but was fine for general trail centre use.
2021 Specialized Stumpjumper Expert bottom line
It’s pretty clear the 2021 Stumpjumper is a great bike for the keen mountain biker; someone who wants to ride a host of different trails whether that’s at a trail centre, on long bridleway-based epics or rolling singletrack.
It’s not quite perfect and it would be great to see an option with a burlier Fox 36 or RockShox Pike fork – like the outgoing model – and longer travel dropper posts, too.
On the flip side, if you’ve got an appetite for more extreme riding, Specialized makes a bike for that. It’s called the Stumpjumper Evo.
With that in mind, as a do-it-all trail bike, Specialized has hit a hole in one with the 2021 Stumpjumper. It seems to strike a balance between XC weight saving, competent trail-based geometry and some burlier parts.
|Weight||12.65kg (S4) – S4, without pedals|
|What we tested||Specialized Stumpjumper Expert|
|Features||SWAT Door integration, BB adjustment, 12x148mm Boost axle|
|Tyres||Specialized Butcher GRID, Gripton 2.3x29in (f), Specialized Purgatory GRID, Gripton 2.3x29in|
|Stem||Specialized Alloy Trail|
|Shifter||SRAM X01 Eagle|
|Seatpost||X-Fusion Manic 170mm drop with SRL LE lever|
|Saddle||Specialized Bridge Comp|
|Rear shock||Fox Float DPS Performance Elite, EVOL, 3-position adjustment with open mode adjust|
|Rear derailleur||SRAM X01 Eagle|
|Handlebar||Specialized Trail 7050 Alloy|
|Available sizes||S1, S2, S3, S4, S5, S6|
|Frame||Specialized Stumpjumper FACT 11M carbon|
|Fork||Foc Float 34 Performance Elite GRIP2, 44mm offset|
|Cranks||SRAM Descendant 7K, 170mm, 30t chainring|
|Chain||SRAM GX Eagle|
|Cassette||SRAM GX Eagle|
|Brakes||SRAM Guide G2 RSC|
|Bottom bracket||SRAM DUB 73mm BSA|
|Wheels||Roval Traverse 29 Alloy rims on Rval hubs|