Specialized Stumpjumper 15
Wheel Size: 29” (S3–S6) or Mixed (S1–S2)
Travel: 145 mm rear / 150 mm front (S1 gets 140 mm front; Ohlins Coil build gets 160 mm front on all sizes)
Geometry Highlights:
- Sizes Offered: S1, S2, S3, S4, S5, S6
- Headtube Angle: 63° (Low), 64.5° (Mid), 65.5° (High),
- Reach: 475 mm (S4, Mid headset cup position)
- Chainstay Length: 435 mm (S4)
Frame Material: Carbon fiber
Price:
- Complete bikes starting at $5,500 USD
- S-Works frameset: $3,500 USD
Intro
It’s hard to think of a more iconic bike lineage than the Specialized Stumpjumper. My first proper mountain bike was a blue 1998 Stumpjumper M2 Comp handed down from my dad, and a chronological look at changes in the Stumpjumper’s design shows just how far mountain bikes have come in a relatively short while.
The prior-generation Stumpjumper had a fairly lengthy run, released in 2020 (MY2021). At least here in the Pacific Northwest, the EVO version of that latest Stumpjumper seems to be on the back of every other truck in the parking lot, with geometry adjustments and a Goldilocks 150 rear travel / 160 front combination that worked well for a huge swath of riders.
But now there’s a new Stumpjumper with a revamped frame design, geometry adjustments, and some new suspension tech called GENIE — and the longstanding Evo version is no more. There’s a good bit to talk about here, so let’s get right to it.
The Frame
At least for now, Specialized’s new Stumpjumper 15 does away with the split between the Stumpjumper and Stumpjumper EVO. The frames are also only available in Specialized’s FACT 11m carbon for now, though we’d put money on an aluminum option coming later.
Though the suspension is still a four-bar layout with a yoke driving the shock, Specialized has made some changes to the kinematics. Anti-squat is now between the levels offered by the outgoing Stumpjumper and Stumpjumper EVO, at roughly 105% at sag before falling off to under 78% at bottom out. That’s not low by any means, but it’s also not as high as a number of other bikes in the Trail segment, and we’ll be curious to see what that means as far as the balance between responsive pedaling and rear wheel tracking under power.
We’ll talk more about sizing down below, as the smallest S1 and S2 sizes get mixed wheels while larger sizes are full 29”, but it’s worth noting that all sizes of the new Stumpjumper are both 29” and mixed wheel compatible via a swappable link. Specialized is making those links available aftermarket so that riders can swap wheel size configurations as they see fit.
The SWAT box that is nearly ubiquitous on Specialized bikes gets updated as well to the 4.0 generation seen on the Epic 8. Specialized is offering lifetime replacement of pivot bearings for the original owner across all models — a nice feature for folks who plan to keep their Stumpjumper for the long haul.
GENIE Rear Shock Concept
One of the most significant changes with the new Stumpjumper is the GENIE rear shock technology — a new air spring design that effectively varies the volume of the rear shock throughout the stroke to blend the benefits of high- and low-volume spring designs in different scenarios. Understanding the proposed benefit here requires a bit of background on air spring design and tradeoffs, so let’s briefly dip into those more technical details before we get into GENIE.
Air springs have changed massively over time and with a lot of nuance, but in their simplest form, air springs employ two opposing air chambers, positive and negative, which affect the spring curve based on their proportional size. Negative springs are critically important to the early stroke feel of an air shock, but it’s the positive side where the GENIE gets interesting,, so we’ll focus there.
Most air-sprung shocks on the market use a fixed positive air volume, which can be adjusted using volume spacers. In the simplest terms, smaller volume shocks have much more progression, meaning that the force required to compress the shock increases significantly from the start to the end of travel. Because much of the air spring ramp-up comes at the end of the curve, that means that there’s often a compromise in getting adequate early and mid-stroke support versus being able to use full travel. Larger volume shocks have a more linear rate of progression, but the tradeoff with that more linear progression rate is that they can often lack support at the end of the travel. Cramming a bunch of volume spacers in the shock can help with that end stroke support, but essentially introduces the tradeoffs of a smaller volume shock.
Enter Specialized’s new GENIE concept. Working with Fox, Specialized has developed a proprietary way of having a rather high-volume air chamber which is reduced to a smaller volume in the final 30% of the shock’s stroke. With the GENIE shock, an inner air chamber is accompanied by a secondary outer sleeve that effectively creates a secondary, but attached air chamber that increases overall volume and creates a more linear air spring curve. At 70% through the travel, a sliding internal band blocks off the shock’s outer air chamber by covering the ports connecting the two chambers, closing off that external sleeve and shrinking the overall air volume. This abruptly shrunken available air volume creates a sudden increase in spring progression, resulting in a shock that starts off with a more linear air spring characteristic but ends as quite a progressive one.
It’s important to note that some shocks, like the EXT Aria, and several forks (Ohlins RXF 38, Manitou Mezzer, EXT Era) use a dual positive spring setup to allow more customization of that spring curve, with a secondary positive chamber that can be run at higher pressures to create a smoother and adjustable end-stroke ramp up. Those chambers, however, are ultimately still separate and require tuning of relative air pressures to get the desired behavior. Compared to these rare and often rather expensive designs, the GENIE system simplifies things by requiring the adjustment of only a single air valve.
Specialized makes some pretty bold claims about this new tech, including promises of “57% less traction loss” and “39% fewer severe bottom-out events” relative to a standard air spring. Relative to the outgoing Stumpjumper EVO, the Stumpjumper 15 claims to use 16.3% more travel for a given impact, indicating a greater response to impacts. We typically don’t put much stock in claims like these because of the nuances of riding style, setup preferences, etc., so we’ll have to see for ourselves just how the new system performs on the trail.
As a final note here, the GENIE-equipped shock is only available as an inline option (i.e., no piggyback for extra oil volume) based on the Fox Float shock, so it will be interesting to see how the big claims of performance hold up on more sustained and rough descents where inline shocks can start to heat up.
Fit & Geometry
Unsurprisingly, the new Stumpjumper follows Specialized’s S-Sizing concept, which encourages riders of different sizes to select a frame size based on individual proportions and riding preferences. While it’s really not functionally different from a typical Small, Medium, Large, etc. approach, it can help folks who tend to think “I’m a Large” consider geometry more fully when picking a frame size.
Folks familiar with the prior Stumpjumper EVO will recognize the familiar 2-position flip chip at the pivot between the chainstay and dropout. This allows for a 7 mm swing in bottom bracket height between Low and High settings, while an eccentric headset cup allows for 3 headtube angle options: 63° (Low), 64.5° (Mid) and 65.5° (High).
Outside of those adjustments, most geometry figures are in the range of what we’d consider normal for a modern Trail bike. With the reference position of the headtube in the Mid position and bottom bracket in High, the S4 gets a 475 mm reach, 640 mm stack, rather substantial 38 mm bottom bracket drop, and short 435 mm chainstays. Full geometry figures are included in the chart below:
The Builds
Specialized’s builds for the Stumpjumper are rather intriguing in their mix of both lightweight and perhaps unexpectedly burly components. The first standout item is that all builds (except the TRP-equipped Ohlins Coil build) feature SRAM’s very powerful Maven brakes, and with a 200 mm front rotor no less. S1–S2 sizes get a smaller 180 mm rear rotor where S3+ sizes get a 200 mm one, but no matter how you look at it, that’s a whole lot of brake for a 145 mm rear travel bike. The Ohlins Coil gets TRP DH-R EVO brakes with a whopping 220 mm rotor up front and 203 mm out back on all sizes.
Speaking of SRAM, cable-loving luddites among us will be saddened to know that the electronic revolution is officially here — with the Stumpjumper 15, every model gets SRAM’s Transmission in GX, X0, or XX trim depending on the build.
Specialized has done well to include long droppers on all sizes of the Stumpjumper. The Comp, Ohlins, and Expert builds see the S1 size get 125 mm drop, while S2 gets 150 mm, S3 gets 170 mm, and all S4 and above get 200 mm (or 190 mm on the Comp’s X-Fusion post). Pro builds come with Bike Yoke Revive MAX posts that eke out a bit more travel at each size (S2 gets 160 mm, S3 185 mm, S4+ 213 mm), but unfortunately the spendy S-Works Stumpjumper comes with the Reverb AXS which still maxes out at 170 mm.
Despite the hype around the new GENIE shock, Specialized hasn’t abandoned coil shock lovers. The Ohlins Coil build is the closest thing to an EVO build offered with the new Stumpjumper, with a TTX22 M.2 rear shock and an Ohlins RXF38 M.2 up front set to 160 mm travel. That’s quite the burly suspension spec for a bike with 145 mm rear travel.
Highlights from each model’s available builds are as follows:
- Drivetrain: SRAM GX Transmission
- Brakes: SRAM Maven Bronze (w/ 200 mm front rotor, 180 mm rear on S1–S2 and 200 mm on other sizes)
- Fork: Fox 36 Rhythm (S1: 140 mm travel, all others: 150 mm)
- Shock: Fox Float Performance GENIE
- Wheels: Specialized alloy rims w/ sealed cartridge bearing hubs (S1–S2: mixed wheels, S3–S6: full 29”)
- Dropper Post: X-Fusion Manic (S1: 125 mm, S2: 150 mm, S3: 170 mm, S4–S6: 190 mm)
- Drivetrain: SRAM GX Transmission
- Brakes: SRAM Maven Bronze (w/ 200 mm front rotor, 180 mm rear on S1–S2 and 200 mm on other sizes)
- Fork: Fox 36 Performance Elite (S1: 140 mm travel, all others: 150 mm)
- Shock: Fox Float Performance Elite GENIE
- Wheels: Roval Traverse w/ DT Swiss 370 hubs (S1–S2: mixed wheels, S3–S6: full 29”)
- Dropper Post: PNW Loam (S1: 125 mm, S2: 150 mm, S3: 170 mm, S4–S6: 200 mm)
- Drivetrain: SRAM GX Transmission
- Brakes: TRP DH-R EVO (w/ 220 mm front rotor, 203 mm rear)
- Fork: Ohlins RXF38 M.2 (160 mm)
- Shock: Ohlins TTX22 M.2
- Wheels: Roval Traverse w/ DT Swiss 370 hubs (S1–S2: mixed wheels, S3–S6: full 29”)
- Dropper Post: PNW Loam (S1: 125 mm, S2: 150 mm, S3: 170 mm, S4–S6: 200 mm)
- Drivetrain: SRAM X0 Transmission
- Brakes: SRAM Maven Silver (w/ 200 mm front rotor, 180 mm rear on S1–S2 and 200 mm on other sizes)
- Fork: Fox 36 Factory GRIP X2 (S1: 140 mm travel, all others: 150 mm)
- Shock: Fox Float Factory GENIE
- Wheels: Roval Traverse SL carbon w/ Industry 9 1/1 hubs (S1–S2: mixed wheels, S3–S6: full 29”)
- Dropper Post: Bike Yoke Revive MAX 3.0 (S1: 125 mm, S2: 160 mm, S3: 185 mm, S4–S6: 213 mm)
- Drivetrain: SRAM XX Transmission
- Brakes: SRAM Maven Ultimate (w/ 200 mm front rotor, 180 mm rear on S1–S2 and 200 mm on other sizes)
- Fork: Fox 36 Factory GRIP X2 (S1: 140 mm travel, all others: 150 mm)
- Shock: Fox Float Factory GENIE
- Wheels: Roval Traverse SL carbon w/ DT Swiss 240 hubs (S1–S2: mixed wheels, S3–S6: full 29”)
- Dropper Post: RockShox Reverb AXS (S1: 125 mm, S2: 150 mm, S3–S6: 170 mm)
In addition to the complete builds, Specialized also offers an S-Works frameset version priced at $3,500, which comes with a Float Factory GENIE shock.
Some Questions / Things We’re Curious About
(1) How does the feel of the novel GENIE shock compare to more conventional layouts, both in terms of performance and setup?
(2) How easy and impactful are the myriad adjustments baked into the new Stumpjumper?
(3) With the outgoing Stumpjumper and Stumpjumper EVO having different personalities and intentions, where does the new Stumpjumper 15 fit on that spectrum as far as ride feel — and where does it differ entirely?
Bottom Line (For Now)
For a lot of folks, the Specialized Stumpjumper and Stumpjumper EVO were an easy quiver-killer choice for folks on the borders of either the Cross Country and Trail or Trail and Enduro categories, respectively. While the new Stumpjumper does away with the EVO designation for now, it remains positioned as a versatile Trail bike with a relatively burly build spec, but with some interesting new adjustments and suspension features. While it seems Specialized hasn’t messed too much with a good thing, those changes have us intrigued — and we should be getting one in for review soon to find out.
Does the frame have the ability to take a mechanical drivetrain with internal cable routing or is this fully setup for electric shifting? I much prefer the gear spacing of Shimano drivetrains.
No provision for a mechanical derailleur. SRAM T-Type has more than a few, shall we say, challenges, but at least they addressed the gear spacing in the lower ranges. But SUCH slow shifting. Argh!
Gotta say, though I’m not a big fan of proprietary rear shocks, this Genie thing is getting really good initial reports. Let’s see what everybody is saying after six months.
Here’s what I would do if I were pondering buying this bike: buy the Stumpy 14 frameset at a KILLER price and build it with a 140 piggy back shock and 150 fork you’re welcome. I ride this now and it slays. Plus its build size allows me to have a super capable TRAIL – not XC, not enduro – bike and add an actual more downhill-oriented bike to the quiver later. There is no “one bike to rule them all.” The quiver can’t be killed! Ha
Specialized, turning on the non standard equipment switch again? It’s a bold move Cotton! Considering the market is currently flooded with 2023 inventory, we’ll see how well this genie floats!
So the big question is: will there be an evo model? Indeed, they don’t say so now, but that doesn’t mean they won’t release it in the future.
Although, historically most Evo versions of Spesh bikes, have had only spec, or perhaps a different rocker link, not a whole different frame. With the upped travel, I would not expect to see a different frame, but where are the Evo builds with a reservoir shock and such?
Can I install a Genie Shock on my 2023 Stumpjumper Pro?
The prior-gen Stumpjumper uses a 190×45 mm shock and the new one goes up to a 210×55 mm one (or 52.5 mm stroke, in the case of the S1) so not for the time being.