Specialized S-Works Stumpjumper 29er

Incredibly stiff, light and hard-edged – in every way

BikeRadar score 3.5/5

Rather than create a high-end 29er carbon hardtail that's equally at home on the racecourse or on longer trail rides, Specialized have gone full gas for the finish line on the S-Works Stumpjumper 29er. It's amazingly light and phenomenally efficient but the punishing ride quality won't suit everyone.

Ride & handling: No wasted energy but rough on the body

Front triangle and drivetrain stiffness on the Specialized S-Works Stumpjumper 29er is incredible. There's no hesitation when you stomp on the pedals and the front end simply will not budge no matter how vigorously you torque on the bars. When you're really trying to make up time, the benefits are obvious as your efforts are rewarded with heaps of instant-gratification speed and there's no sense that you're wasting even a hint of energy. Roadies coming off of high-end carbon machines will find themselves right at home here.

That fantastic front-end rigidity is also a boon for handling reflexes. Especially when combined with the relatively steep 71.5° head angle – a full 2° steeper than the Scott Scale 29 RC we tested earlier this year – tight 435mm chainstays and very low 304mm bottom bracket height, cutting through tight singletrack is as close to a point-and-shoot affair as it comes. 

Riders need to be on their game, though, as the lack of flex and the steep angles mean there's little room for error for any unintended steering input – point and shoot, indeed, but you'd better be careful where you're aiming. The high-speed stability provided by that low bottom bracket requires a little extra attention in technical terrain, too, as we not only smacked the pedals on rocks on numerous occasions but even dragged them on the ground through tight uphill switchbacks from time to time.

Cross-country races are generally won – or lost – on the climbs so it's no surprise that all of this rigidity is bundled with very little mass. Total bike weight without pedals straight out of the box was just 9.33kg (20.57lb) and dropped to a paltry 9.21kg (20.3lb) after trading the chunky inner tubes for a few scoops of NoTubes goop.

That's impressive already, but even more so when you consider that our early production sample came with aluminum wheels instead of the carbon fibre ones on consumer bikes, which would bring the weight down to a simply laughable 8.91kg (19.64lb). So it goes without saying that the S-Works Stumpjumper 29er is the proverbial rocket ship when pointed uphill. Lest your legs, lungs or tires give up the ghost, you certainly won't be able to blame the bike if you're beaten to the top of the climb. 

Adding to the bike's efficiency is the slick Reba S29 fork – a collaboration between Specialized and RockShox that borrows the upper tubes, lower legs and Dual Air spring internals from the latter and combines them with Specialized's own carbon crown, tapered steerer and inertia valve damper for a lightweight, 1,570g package – roughly the same as the upcoming RockShox SID 29 World Cup

Without question, the so-called "Brain" works, moving only as much or as little as you dial in on smoother terrain but nearly instantly opening up at the first impact – then quickly firming up again right afterward. Overall control is good in the fork's active mode, though still not quite as good as the best from Fox Racing Shox or RockShox. And despite Specialized's claims of "size specific" travel – in this case, just 90mm – we definitely missed that last 10mm when trying to rip through technical sections of trail.

This "light and stiff" combination to which Specialized have so faithfully adhered on the S-Works Stumpjumper 29er may be a proven formula on the road but unfortunately, it doesn't quite translate as well to the trail, at least as far as hardtails are concerned. The frame ably damps low amplitude, high-frequency buzz like other good carbon frames but real-world ride quality on dirt simply isn't up to snuff with the bike's other performance attributes despite what the spindly seatstays suggest, even with the supple Renegade low-knob tires inflated to just 25psi.

While rider comfort can be viewed as an optional luxury to some extent when it comes to racing, the S-Works Stumpjumper 29er's overly stout rear end also keeps it from going as fast as it could. Sure, it's incredibly efficient in harnessing your power but it isn't quite as good at effectively putting that power down to the ground unless it's perfectly buffed out. After all, even fully rigid professional shifter karts have flex built into the chassis to enhance traction. 

Maintaining a smooth, seated pedal stroke on rocky terrain is especially difficult and it's also tough to keep the rear end dug in on looser climbs. We found ourselves feeling more beat-up than usual on regular training routes. Some of that razor-sharp handling prowess is similarly wasted, too, as the S-Works Stumpjumper 29er struggles to keep its contact patches on the ground through bumpy corners – this bike will go as fast as you can pedal but unfortunately, you'll have to slow down more, too.

All in all, the Specialized S-Works Stumpjumper 29er is a finely focused race machine with its eyes keenly focused on the prize. That being said, compromises in ride quality and the very quick handling – not to mention the pricetag – limit its appeal to the masses and we'd argue even somewhat hamper its capabilities in a race situation, too.

Frame: Like a Tarmac SL3 but sized for 29in wheels

Specialized's latest Stumpjumper 29er frame upgrades from the 2010 version with a more advanced FACT 11m carbon fiber blend borrowed from the Tarmac SL3 road flagship, hollow carbon fiber instead of aluminum dropouts (but still with alloy faces to protect against knurled hub ends and quick-release skewers), carbon post-mount rear brake tabs, and a new all-carbon PressFit 30-compatible bottom bracket shell. Actual weight for our 17.5in test frame is just 1,070g complete with seatpost collar, rear derailleur hanger and water bottle bolts – nearly 300g lighter than Specialized's best alloy road frame

Given the stiffness goals, tube dimensions are expectedly oversized, especially at the enormous down tube, the very wide and flat top tube, and the tall, slightly asymmetrical chainstays. Naturally, the head tube is tapered from 1-1/8in up top to 1-1/2in down below, though it continues to use Specialized's Campagnolo-style bearing dimensions and tucked-in lower bearing placement, which complicates parts swapping if you're so inclined.

Despite our complaints about the stiff ride of the current version, it's still an improvement over its predecessor, according to Specialized's Eric Schuda. "As far as the ride quality, when we developed this bike one of the criteria was to have a more compliant ride compared to our 2010 SW SJHT 29," he told BikeRadar. "If you compare the two bikes, we're using thinner diameter seatstays on the 2011 and we're also using a 27.2 seatpost which adds quite a bit of compliance. From my personal experience on the two bikes, the 2011 is definitely smoother riding that the 2010."

Equipment: Great SRAM XX drivetrain, awesome Specialized carbon cranks

The build kit is 100 percent race ready out of the box and well in keeping with the personality of the frame. Main players include SRAM's ultralight 2x10 XX group with its superb-shifting rear derailleur and X-Dome rear cassette, and the simply brilliant X-Glide chainrings. Lever action was admirably smooth, light and accurate, with consistently excellent shift performance even under full power and with the added benefit of full-length cable housing to protect against contamination. 

The hydraulic disc brakes come from the XX group, too, though here Avid have provided Specialized with a slightly tweaked version of their lightweight World Cup variant complete with tool-free reach adjust on the carbon lever blades. The 160mm-diameter rotors served up ample stopping power with good modulation for cross-country duties, though as we've noticed with other XX brakes, performance was slightly hit-or-miss due to migrating air bubbles in the system. 

The one notable exception to the XX package is Specialized's own FACT crankset with its massive carbon fiber arms. Despite being wonderfully light, it's tangibly stiffer underfoot than more conventional setups and the stout alloy spider provides a solid foundation for the XX chainrings. Be sure to check the main bolt joining the 30mm-diameter alloy half-spindles, though – ours were frighteningly loose from the factory.

Syntace provide their outstanding F109 forged aluminum stem but the rest of the bike is an all-Specialized affair. The Roval Control 29 wheels (the EL aluminum version on our test bike but the lighter SL on production bikes) are reasonably stout, with DT Swiss star ratchet rear hub internals and easily convert to tubeless. The S-Works Renegade 2Bliss tires are ultra-fast rolling yet still reasonably grippy as long as you're not off in the marbles, the flat carbon bar is refreshingly wide at 680mm and includes eight degrees of wrist-relieving sweep, and it's capped with lock-on grips in size-specific diameters. 

Seating is handled by Specialized, too, with a very firm yet highly supportive and comfortable Body Geometry Phenom saddle and carbon setback seatpost. Specialized's product managers have again done a very good job sweating the details as well. Protective clear vinyl tape is pre-applied to the underside of the down tube and crankarm faces (though ours was already starting to peel after the first ride), the virtually weightless headset cap is held in place with an alloy bolt, and the seatpost collar features a rotating barrel nut and spherical washer beneath the bolt head to keep the titanium fastener properly aligned. 

NOTE: The S-Works Stumpjumper 29er isn't currently available in the UK.

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