Specialized Stumpjumper 15 Pro: first ride review

The 50th anniversary of Specialized brings us the fifteenth Stumpy: here’s our early verdict on the Specialized Stumpjumper 15 Pro.

• Brand: Specialized
• Product: Stumpjumper 15 Pro
• Price: £7,500
• From: Specialized
• Tested by: Benji for 2 days

Pros

• Great handling geometry
• GENIE shock is impressively adjustable
• Not overly stiff frame

Cons

• No more cool side-arm
• Tyres may struggle in wet/UK
• £7,500

Specialized Stumpjumper 15 in a nutshell

• 15th version of the Stumpjumper (the Stumpy debuted in 1981)
• 145mm trail bike
• 150mm fork
• Patent pending GENIE air shock offers impressive tunability
• Full 29er off-the-epg (mullet kit available)
• Lots of geometry adjustment
• Carbon frame
• SWAT 4 frame storage
• Price range: £6,000 up to £10,000

The Stumpjumper is now just one bike again. No more regular Stumpjumper and Stumpjumper EVO options. Just Stumpjumper 15. With that said, it really much more like that the previous regular Stumpjumper has been ditched and the EVO is now the de facto solitary Stumpjumper.

Which sort of begs the question, will Specialized (re)introduce a model to sit between the Epic EVO and the Stumpjumper 15 – a Camber perhaps? I actually have no idea but I wouldn’t be surprised if they did.

Amd does the new Stumpjumper 15 signpost anything as regards a revamped Specialized Enduro? Again, I have no idea or information but one would imagine the Enduro would be going up into 180/190mm super enduro class and sport a GENIE rear shock.

GENIE

Sorry? A what rear shock?

It’s a Fox shock but not as we know it. I shall try and explain it simply because it is actually pretty simple. The GENIE has two positive air chambers (an outer and an inner). For the first 70% of travel, the chambers are connected. Once suspension is compressed deeper than 70%, the ‘GENIE Band’ closes the connection between the two positive air chambers, leaving you just using inner air chamber.

I’ll go into more details about GENIE later. Let’s get back the other stuff.

What else is new?

What else is new on the Stumpjumper 15 compared to the outgoing Stumpjumper EVO?

No more sidearm. Ditching the sidearm has enabled more room for fat shocks (coil piggybacks as well as chonky boi GENIE) and has allowed a reworked seat tube for much deeper dropper post insertion. The S5 I rode had 45mm more dropper insertion than the old EVO, for example. The increase in dropper travel – and the reduction in stem length specced (50 to 40mm) – were the two most immediate things I noticed (and very much appreciated) when riding the new Stumpy 15.

Redesigned rocker linkage. You’ll notice that the main rocker linkage is now one-piece, it extends and ‘joins up’ in front of the seat tube instead of finishing at the seat tube pivot. Think of it as like a triple clamp fork (braced in three spots) instead of a single crown fork (only braced in two). As well as general chassis stiffness, this should alleviate some of the issues with running a yoke driver on a coil rear shock.

SWAT is now in its fourth generation. SWAT 4 has the cover attaching directly to the carbon of the frame; no more plastic rim. It generally looks sleeker and claims to be more a bit resistant to water ingress whilst remaining easy and quick to operate.

Full size water bottles fit all frame sizes by the way.

Geometry

In terms of geometry, there is no wholesale majorly rejig compared to the previous Stumpjumper EVO but there are a few significant tweaks. Stack has increased, especially on the larger sizes. Chain stay lengths vary up to 15mm from S1 to S6. Chain stay length is also adjustable +/-5mm depending which way you set the Horst Link flipchip.

Regarding geometry adjustment, all the stuff you could mess with on the EVO is still present. Head angle can be switched from its 64.5° neutral setting by running a special headset cup (63° or 65.5°). The shock yoke has an offset bushing that raises/lowers the BB height by 7mm. The +/-5mm chain stay flipchip I’ve already mentioned.

Geometry chart

SIZE	S1	S2	S3	S4	S5	S6
STACK	608 mm	618 mm	627 mm	640 mm	654 mm	667 mm
REACH	400 mm	425 mm	450 mm	475 mm	500 mm	530 mm
HEAD TUBE LENGTH	95 mm	100 mm	110 mm	125 mm	140 mm	155 mm
HEAD TUBE ANGLE	63/64.5/65.5 °	63/64.5/65.5 °	63/64.5/65.5 °	63/64.5/65.5 °	63/64.5/65.5 °	63/64.5/65.5 °
BB HEIGHT	327/334 mm	330/337 mm	330/337 mm	330/337 mm	330/337 mm	330/337 mm
BB DROP	41 mm	38 mm	38 mm	38 mm	38 mm	38 mm
TRAIL	129 mm	130 mm	130 mm	130 mm	130 mm	130 mm
FORK LENGTH	551 mm	561 mm	561 mm	561 mm	561 mm	561 mm
FORK OFFSET	44 mm	44 mm	44 mm	44 mm	44 mm	44 mm
FRONT CENTER	720 mm	751 mm	780 mm	812 mm	843 mm	879 mm
CHAINSTAY LENGTH	430 mm	432 mm	435 mm	435 mm	445 mm	445 mm
WHEELBASE	1,149 mm	1,181 mm	1,213 mm	1,244 mm	1,285 mm	1,322 mm
TOP TUBE LENGTH , HORIZONTAL	541 mm	573 mm	595 mm	624 mm	647 mm	677 mm
BIKE STANDOVER HEIGHT	738 mm	751 mm	745 mm	745 mm	745 mm	751mm
SEAT TUBE LENGTH	385 mm	385 mm	405 mm	425 mm	445 mm	465 mm
SEAT TUBE ANGLE	77.0 °	76.5 °	77.0 °	76.9 °	77.3 °	77.6 °
SEAT POST MAX INSERTION	245 mm	245 mm	255 mm	255 mm	285 mm	285 mm
SEAT POST MIN INSERTION	80 mm	80 mm	80 mm	80 mm	80 mm	80 mm

The Stumpjumper 15 is a full 29er bike but you can run it as a mullet via an aftermarket link kit. You’ll also have to provide the rear wheel and tyre. I dare say they’ll be some folk who get this mulleting kit as run the bike still in full 29 spec (doing some attendant geo tweaking elsewhere) to raise the BB and steepen the seat angle even more. Kudos to Specialized for making such things possible. It’s interesting, easy and fun to mess about – to us geo tweekers anyway.

In terms of suspension kinematic, with the GENIE shock very much being The Big Thing here, the changes to the frame kinematic are minimal. Essentially the only significant thing is a reduction in anti-squat compared to the outgoing EVO, making the Stumpjumper 15 slightly more active under pedaling.

One thing that is easily missed is that Specialized offer a lifetime, no-questions-asked bearing replacement policy. Which is nice.

Another easily missed aspect is that the rear travel has reduced by 5mm, if we’re comparing the Stumpjumper 15 to the old EVO (150mm) anyway. Compared to the previous regular Stumpjumper (130mm) it’s increased 15mm.

Build kit

Before I return to delve into the GENIE stuff, a quick rundown of the build kit that came on the Specialized Stumpjumper 15 Pro test bike I rode, because it undoubtedly has an effect on the whole experience.

The fork was the first time I’ve properly had a try on a Fox 36 with the new GRIP X2 damper. Perhaps unsurprisingly, but still pleasingly, the 36 was great. A little bit firmer in a sporty sort of way but still grippy and not shy of giving you a decent amount of travel as and required.

It was also the first time I’d tried the new SRAM Maven brakes. Yes, they are flipping powerful. I did feel they required a tiny bit more effort to get the lever moving but in terms of control and modulation I was relieved to find out that Mavens aren’t the lethally binary ON/OFF endo-makers that some people say they are. They’re ‘just’ super modern disc brakes. Which are amazing.

The in-house carbon wheels and Grid Trail casing tyres were fast running little units and did fine in the conditions I encountered. The tyres require running quite hard to stop them folding, which is fine when the conditions allow. I’d be putting more capable rubbers on for typical UK usage.

The Eagle AXS drivetrain worked as it always does; perhaps a bit laggy feleing if you’re coming from a high-end cable-actuated system, but no misfires and no letting-off-the-gas required. I personally really like AXS, so there.

The BikeYoke Revive Max dropper was of a decent length (213mm). Finally having a 200mm+ dropper on a Specialized really is like unlocking some sort of Special Move. Specialized bikes have always had decent standover so to have that finally, fully combine with a saddle that disappears properly is a really massive improvement.

Finally, kudos to Specialized for the contact points. The aforementioned shorter stem is a good move (though I’d still prefer a shorter than 40mm one – sorry). The bars are wide, comfortable and have a decent enough rise to them – thanks to the increase in stack/head tube length. The wide in-house saddle was invisible. Even the Deity Lockjaw grips were nice (unlike previous years’ own-brand harshies).

GENIE (slight return)

Right then. GENIE time.

Proprietary and/or patented shock technology will always get some people’s backs up. I can understand why. It’s a commitment to an unknown. So what I would say early on is: you can run any rear shock you want on the Stumpjumper 15. It’s a regular 210x55mm shock.

(Conversely, I’m sure there will be plenty of existing Specialized owners who’ll be interested in running a GENIE shock on their ‘old’ bikes).

Indeed, the fact that the Stumpjumper 15 Öhlins Coil uses a coil rear shock is illuminating, in a number of ways. Firstly, it confirms that GENIE isn’t as oddball as you may expect (familiar damping dials and volume spacers). Secondly, it tells us a bit about the nature of GENIE in general; namely that GENIE is the latest attempt to get an air shock to behave like a coil shock.

Does it work? Yes and no. Mostly yes. I didn’t feel it was quite as free-moving supple as a coil shock but it was certainly better than some air shocks that rely on large negative air chambers to make the shock supple that then consequently lack mid-stroke and then have far too much ramp end-stroke to be useable/useful.

Having said that, it’s undeniable that the GENIE can be set up in many, many more ways than a coil can. In a spring curve sense at least. You’d have to have a coil with some sort of hydraulic bottom out capability to get the same sort of end-troke progression adjustment that’s possible with the GENIE.

To my mind then, GENIE was much more about the mid-stroke. Specifically, about having a say in how the mid-stoke behaved.

If you want the GENIE to behave like a modern large negative chamber air shock, remove the volume spacer (the bike ships with one installed) from the outer chamber. If you want maximum midstroke support, fill the outer chamber with four spacers. Or go somewhere in between. No special tools are required for volume spacer messing. You don’t even have to remove the shock from the bike.

There can also mess with volume spacers in the inner positive chamber, although it’s a bit more of fiddly job that’s best done with the shock removed from the bike. This is how you can tweak the endstroke bottom-out performance. So yes, you could fill the outer chamber with spacers, remove all the spacers from the inner chamber and imitate the linear curve of a coil.

In terms of external adjustments, the Fox Float Factory GENIE shock on the bike I rode had a low speed rebound dial and a climb switch (with the Open setting also having three settings).

The frame

In all this hullabaloo about GENIE and stuff, I’ve not really talked about the frame. Oops! This is partly because the Stumpjumper 15 still very much looks like a Specialized and that’s very easily taken for granted. Suffice to say, it’s all very nicely executed.

The most obvious change is the lack of a side-arm strut. But keen Spesh watchers will also quickly spot the new wrap-around rocker and the ‘new bends’ in the seat tube and down tube. The seat tube bend is what enables the insertion of loger travel dropper posts. The down tube bend gives the space for full size water bottles.

Cable routing is internal as you’d expect but there is zero use of thru-headset nonsense. See? It can (not) be done! Other supposed mountain bike designers take note.

What else? 34.9mm seat tube diameter. Threaded BB. UDH hanger.

How does it ride?

I only had two days testing the new Specialized Stumpjumper 15 Pro so am not going to try and come out with a definitive take on the bike. Having said that, the testing took in nearly 40km/2000m so it was a better test period than most press launches.

The first thing I’d say is that the Stumpjumper 15 very much retains the easy-to-ride vibe of the outgoing Stumpjumper EVO. Despite all the carbon this and the GENIE that, the bike was not daunting or unfriendly. Everything felt in the right place. Nothing had to be ‘born in mind’ or factored in. I could hop on the Stumpjumper 15 and just ride it around.

Which in one sense may sound meaningless – if not borderline moronic – but this approach-ability of the new Stumpy very much reminded me of the Stumpy EVO we tested a couple of years ago. I’m very pleased to find it’s still there.

Ultimately, any bike with 500mm reach, 450mm chain stays, 140mm head tube, circa 64° head angle and 77° seat angle is a bike I’m probably going to get along with. But I don’t think I’m an outlier. I think most riders will be well served by the geometry formulae applied across the size range.

I would say that I found the new Stumpjumper 15 to feel a bit ‘softer’ than I remember the old EVO being. I don’t think there’s just one simple factor at play here. It’s no doubt a combination of all sort of things (frame flex, reduced anti-squat, dampers, wheels, cockpit stuff…) but nevertheless it’s a very welcome softening. It makes the bike faster. And even more confidence inspiring.

Although the geometry charts don’t really suggest as such, the climbing position felt more efficient than the EVO. The extra handful of mm on the chain stays (I ran them in the Long setting after a while) won’t have done any harm but I suspect it was the increased support in the rear shock that was I noticing.

Clearly, the main thing of interest to most people is going to the GENIE rear shock. The sheer adjustability of the GENIE shock means getting a proper handle on it within a couple of days of riding (on unfamiliar terrain) isn’t really viable. But here goes…

I think the main thing I felt about GENIE was that it was pretty much like being able to have multiple bikes in one. The generally 4-bar layout of the Stumpjumper 15 is extremely neutral and thus it’s the GENIE shock that’s doing most of the work in terms of changing the ride characteristics.

Running it with just the one volume spacer in the outer chamber felt fine. So if you just want to ride a bike and get on with your life, leave the bike as it comes. You don’t have to do anything to ride the GENIE. It’s just a shock. Set your sag, set your rebound, use the climb switch if you want to. Crack on.

If you do like to mess about with your suspension – kinda like how you can mess around with the Stumpy 15’s geometry with all the flip chips and headset cups – then I think you’ll find a lot to enjoy about GENIE.

Running it with zero spacers in the outer chamber made it ride like some other modern mountain bikes with air shocks ie. with a ‘soft>absent>hard’ aspect to the travel usage. Running it with the maximum amount (four) of spacers really firmed things up and made for an excellently sporty ‘rally car’ feel but could also lead to a bit much harshness in unexpected rough stuff. I think I’m a two, probably three, spacer kinda guy.

Early verdict

Putting aside the GENIE rear shock stuff for a moment, the new Specialized Stumpjumper 15 feels like a bike that is so… obvious, that it’s hard to fathom why so few other brands can do bikes like this. The new Stumpy manages to be a customer-pleasing box-ticker (modern geometry, decent dropper insertion, bottle space, frame storage, shorter stem, no thru-headset cable routing) whilst also still being quintessentially Stumpjumper in its capabilities. The GENIE shock needs more mileage put through it (by me) before I’d publish a finished verdict but all the signs are there that the designers know what they’re doing.

Other models:

S-Works Specialized Stumpjumper 15

• FACT 11m carbon chassis, rear-end, and link
• Roval Traverse SL wheels, DT Swiss 240 hub
• Ride Dynamics tuned FOX FLOAT Factory with Specialized GENIE Shock Tech
• FOX FLOAT 36 Factory fork with GRIP X2 damper
• SRAM XX Eagle T-Type AXS drivetrain
• SRAM Maven Ultimate 4-piston brakes
• RockShox Reverb AXS dropper post
• SRP £10,000

Specialized Stumpjumper 15 Öhlins Coil

• FACT 11m carbon chassis and rear-end
• Roval Traverse wheels with DT Swiss 370 hub
• Öhlins TTX 22 M Coil, Ride Dynamics tuned
• 160mm Öhlins RXF38 M.2 29 fork
• SRAM GX Eagle AXS T-Type drivetrain
• TRP DH-R EVO 4-piston brakes
• Adjustable travel PNW LOAM dropper post
• SRP £7,000

Specialized Stumpjumper 15 Expert

• FACT 11m carbon chassis and rear-end
• Ride Dynamics tuned FOX FLOAT Performance Elite with Specialized GENIE Shock Tech
• FOX FLOAT 36 Performance Elite fork with GRIP X2 damper
• Roval Traverse wheels, DT Swiss 370 hub
• SRAM GX Eagle T-Type AXS drivetrain
• SRAM Maven Bronze 4-piston brakes
• SRP £6,000

Specialized Stumpjumper 15 Pro specification

• Frame // FACT 11m Carbon, 145mm
• Shock // Fox Float Factory GENIE, 210x55mm
• Fork // Fox Float 36 Factory GRIP X2, 150mm
• Wheels // Roval Traverse SL Carbon
• Front Tyre // Specialized Butcher Grid Trail T9, 29×2.3in
• Rear Tyre // Specialized Eliminator Grid Trail T7, 29×2.3in
• Chainset // SRAM X0 Eagle, 170mm, 32T
• Brakes // SRAM Maven Silver 200/200mm
• Drivetrain // SRAM X0 Eagle AXS, 10-52T
• Stem // Industry 9 Mountain 35, 40mm
• Handlebars // Roval Traverse SL Carbon, 800x30mm
• Grips // Deity Lockjaw
• Seat Post // BikeYoke Revive Max, 213mm, 34.9mm
• Saddle // Specialized Bridge Expert MIMIC
• Weight // 14.26kg (actual)

Geometry of our S5 size

• Head angle // 63°/64.5°/65.5°
• Effective seat angle // 77.3°
• Seat tube length // 445mm
• Head tube length // 140mm
• Chainstay // 445/450mm
• Wheelbase // 1,285mm
• Effective top tube // 647mm
• BB height // 38mm BB drop
• Reach // 500mm

Review Info

Brand:	Specialized
Product:	Stumpjumper 15 Pro
From:	Specialized
Price:	£7,500
Tested:	by Benji for 2 days