First ride: Specialized 2025 Stumpjumper has new dual-chamber air shock

Features of the framework

Things here look pretty similar to the last-gen EVO, with push-on earcups that allow ±1° of head angle adjustment, a high/low rotary chip to change the height of the bottom bracket and the angle of the head tube/seat tube, and an aftermarket swivel that allows you to use a different sized rear wheel. This last item only applies to bikes sized S3 and larger, as the S1 and S2 options are only mixed wheels.

The Stumpjumper includes SWAT 4.0, Specialized’s most refined in-frame storage solution yet. First seen on the Epic 8, this newest iteration of the SWAT eschews any redundant frame-mounted hardware, and instead the hatch door interacts directly with the frame’s carbon, ensuring a comfortable, long-lasting fit long and excellent weather sealing.

One new detail on the Stumpy that’s sure to raise some eyebrows is the elimination of the mechanical cable routing of the steering system – this bike only moves by waves. The argument from their development team is that they believe the highest shifting performance available comes from systems like SRAM Transmission, and that the best is what people deserve on this bike.

The bike uses a 200mm rotor rear brake setup, which is a little surprising considering the fact that almost all Stumpjumper builds come with SRAM Maven brakes – they can deliver a lot of power on a smaller 180mm rotor. That said, their 200 front and rear steering never felt excessive on this bike.

Geometry

Like the outgoing Stumpy EVO, the Stumpjumper 15 implements a wide range of geometry adjustments baked into the frame. The head angle can deviate 1° in either direction from the stock 64.5° position, via a set of easily replaceable cups that come with the frame. The flip chip on the chainstay allows the rider to raise or lower the bottom bracket height by 7mm, while also changing the head and seat angle by 0.5°. All of this together makes for a very wide range of adjustments, so I’ll stick to the stock numbers for now, which have to do with the mid-head angle and high-roll chip position.

As mentioned above, the new Stumpjumper’s head angle is 64.5° – slack enough for just about anything, while still maintaining nimble handling in flatter corners. The effective seat angle in all sizes falls around 77°, although the actual angle the seat tube throws is slower than this figure, sitting somewhere around 70°. Reach figures range from 400mm to 530mm across the 6-size range, with 25mm jumps between all but the largest size, which scales by 30mm. The stack heights are very high on the Specialists, with the head tube length increasing quite significantly on the larger sized bikes.

Bottom bracket drop is 38mm on all but the S1 bike, which is 41mm. Chain lengths are scaled across the range, with lengths in all six sizes set as follows: 430mm, 432mm, 435mm, 435mm, 445mm, 445mm. Again, many of these figures can be modified by the end user, with a variety of possible results as an experiment with combinations.

Suspension design

In many ways this is a familiar story, but the characters involved have evolved slightly to allow for a different outcome. Our main character – the dude – is the most significantly changed item in the game here, with some new technology allowing for very linear cinematics.

We learned a lot from developing the Levo SL in terms of leverage. By moving to a slightly lower starting point and slightly less progression than our previous bikes, we saw improvements in consistency and control in ride feel throughout the travel range, regardless of stroke type. It also helped to slightly lower shock pressures and bring a little more ease to the shock setup process. The SL naturally developed around standard shocks without the Genie technology being invented at that point. As we went into the Stumpjumper 15, we wanted to bring these features, again, regardless of the type of shock, so you can see the similarities between the Levo SL and the SJ 15 (we’re a bit more progressive on the SJ 15). This leverage rate works great with standard shots and also really helps highlight what Genie brings to the table. We don’t need more advance in the early part of the stroke with the extra volume, and the adjustable secondary spring ramp is extra insurance for any rider looking for maximum support later in the ride. –Steve Saletnik

Jin’s friend

Given the linear nature of the Stumpjumper 15, it may seem necessary to apply a fairly progressive spring to keep the bike from bottoming out hard and often. However, the team behind the bike went in a different direction and instead devised a shock that makes the most of that linear rate of leverage. The first key element here is the mass volume of the shock air. This accounts for the beer can-sized outer sleeve of air, called the extra volume (EV) chamber. For the first 70% of the travel, the shock’s internal air chamber and EV sleeve act as an air source, slowly inflating as you compress along the bike’s travel. At that 70% point, a sliding clutch inside the shock closes off the EV chamber, isolating the much smaller internal air chamber. This creates a much more progressive air chamber, allowing the shock to build up in that last 30% of travel and preventing you from running at the bottom of the travel.

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Specialized Ride Dynamics – the group responsible for developing the Genie shock – called this coilover sliding technology Pneumatic Spring Assist. The possibilities this technology unlocks extend far beyond just this friend, as laid out in this patent filed last year.

The Specialized Ride Dynamics team tested a wide range of build options with early versions of the Genie shock in order to make a decision on factors such as the transfer point between large and small air volume and whether to build or not friend in a piggy bank. platform. Ultimately, they settled on Float as a base for the technology because any added benefit of the extra volume of oil in a crushed stroke felt insignificant compared to the benefits of the increased air volume. Fortunately, the Float is also a widely available companion with great parts availability, so spares for any necessary service will be easy to find.

While this clever technology allows the Genie shock to optimize performance for the kinematics on the Stumpjumper 15, it’s not like the bike won’t work with other, more typical shocks. I had the opportunity to test the bike side-by-side with the Genie and other stock offerings, and although the custom-fit shock seemed more appropriate, the stock options performed quite well.

Building kits

All carbon, all the same build, but with lots of part differences to differentiate the different build levels. The S-Works frame differs slightly in the use of a carbon fiber swingarm to save weight, but otherwise the frames are the same across the lineup. Every bike, with the exception of the Öhlins build, comes with a Genie shock.

Ride Impressions

For the past couple of months, the Stumpjumper has been my go-to ride for hot day rides and longer rides alike. That shows how much I’ve liked the bike so far, but also speaks to the fit of the platform. Mature tweaks to the geometry and suspension can radically change the bike’s character, taking it from a sharp-feeling trail bike to a downhill drag, all within the parameters of stock components. In terms of geometry, I think the stock position is the best for me and my riding terrain. The 64.5° head tube angle handles intuitively on a wide range of trails and still feels reliable on very steep terrain. This is helped by the ample stack height, which keeps you in a strong vertical position with good weight through the bars. My one quibble is with the seat tube angle, which feels too weak to me. This is likely due to my fairly high seat height and current seat tube angle.

I owned the previous alloy Stumpjumper EVO for years and fondly remember the many good rides I had on that bike. This one is better, mostly in the bump-sucking department. The geometry is quite similar between the two, but the Stumpjumper 15’s ability to stay composed over very rough terrain is truly impressive. The bike also generates surprising grip for a 145mm bike, putting it in strong competition with the longer travel bikes in my garage. While the suspension feels quite active, I never found it vague or vague in pumping scenarios – it just moves more than you’d initially expect. For those who want a smaller bike feel, it’s as simple as adding more spacers to the extra volume shock chamber and dialing up the air pressure.

Last weekend, I went for a ride that just might highlight the Stumpy’s comfort, capability and a solid bike. At about 95 miles and 18,000 feet of climbing, this was one of the biggest rides I’ve done in recent memory, and I feel like I picked the perfect bike for the mission. There were no gentle descents on the map, each with its own character and terrain differences. Running the bike on the stock geometry setup, with 1 spacer on the shock, it felt like enough of a bike to hit some serious features along the way, while remaining efficient enough not to add extra work during the day. Dropping random stats isn’t so much to inflate my puny ego as to illustrate the full nature of the Stumpjumper – the ride felt comfortable and fun all day. Of note, I played with the easily accessible lockout switch on a few fire road climbs, but ultimately preferred the open shock climb.

I have many other thoughts on this bike, but I’ll try to save most of them for the full review. Stay tuned for that, as this bike is sure to see a lot of changes as I continue to play with the setup and adjustments.