First Ride: 2025 Specialized Stumpjumper Gets New Dual Chamber Air Shock – Pinkbike

Frame properties

Things here seem pretty similar to the previous-generation EVO, with press-in headset cups that allow for ±1° of head angle adjustment, a high/low flip chip for altering bottom bracket height and headtube/seat tube angles, and an aftermarket rocker link that allows you to run a different size rear wheel. That last item only applies to bikes size S3 and up, as the S1 and S2 options are mixed-wheel options only.

The Stumpjumper features SWAT 4.0, Specialized’s most refined in-frame storage solution to date. First seen on the Epic 8, this latest iteration of SWAT eschews any unnecessary hardware attached to the frame and instead has the hatch door connect directly to the frame’s carbon for a great fit, durability, and excellent weather sealing.

One new detail on the Stumpy that’s sure to raise some quibbles is the elimination of mechanical drivetrain cable routing – this bike shifts wirelessly only. Their development team’s argument 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 native post rear brake mount, which is a little surprising considering that nearly all builds of the Stumpjumper come with SRAM Maven brakes – they can put out plenty of power off a smaller 180mm rotor. That said, it never felt excessive to run them with 200s front and rear on this bike.

Geometry

Like the outgoing Stumpy EVO, the Stumpjumper 15 implements a wide range of geometry adjustments built into the frame. The head angle is capable of being varied by 1° in either direction from the stock position of 64.5°, via a set of easily interchangeable cups that ship with the frame. A flip chip on the chainstay allows the rider to raise or lower the bottom bracket height by 7mm, while also altering the head tube and seat angles by 0.5°. All of this combines to create a very wide range of adjustment, so I’ll stick with the stock numbers for now, which refer to the mid-head tube angle and high flip chip position.

As mentioned above, the new Stumpjumper’s head angle is a slack 64.5° – slack enough for just about anything, while still maintaining agile handling at flatter angles. The effective seat angle on all sizes sits around 77°, though the actual angle the seat tube makes is slacker than that figure, somewhere around 70°. Reach figures range from 400mm to 530mm across the size 6 range, with 25mm jumps between all but the largest size, which climbs by 30mm. Stack heights are very tall for Specialized, with the headtube length increasing quite a bit on the larger bikes.

Bottom bracket drop is 38mm on all bikes except the S1, which measures 41mm. Chainstay length is consistent across the range, with the lengths across all six sizes being: 430mm, 432mm, 435mm, 435mm, 445mm, 445mm. Again, many of these numbers are adjustable by the end user, with a variety of possible outcomes if one experiments with the combinations.

Suspension design

In many ways this is a familiar story, but the characters involved have evolved somewhat to allow for a different outcome. Our main character – the Shock – is the most significantly changed item here, with some new technologies allowing for very linear kinematics.

We learned a lot from the development of the Levo SL in terms of leverage. By going to a slightly lower starting point and slightly less progression than our previous bikes, we saw improvements in consistency and control in the feel of the travel throughout the entire range of travel, regardless of shock type. It also helped to lower the shock pressure slightly and make the shock setup process a little easier. Of course, the SL was developed around standard shocks without Genie technology being invented at the time. When we broke in the Stumpjumper 15, we wanted to include these features, again regardless of shock type, so you can see the similarities between the Levo SL and SJ 15 (we’re a little more progressive on the SJ 15). That leverage works great with stock shocks and really helps accentuate what the Genie has to offer. We didn’t need the extra progression up front with the added volume, and the adjustable secondary spring rate is added insurance for any riders looking for maximum support later in the travel. —Steve Saletnik

The Genie Shock

Given the linear nature of the Stumpjumper 15, it might seem like it would need a fairly progressive spring rate to keep the bike from bottoming out hard and often. However, the team behind the bike went in a different direction and instead came up with a shock that makes the most of that linear leverage. The first key element here is the shock’s massive air volume. This is responsible for the beer can-sized outer air sleeve, called the Extra Volume (EV) chamber. For the first 70% of the suspension’s travel, the shock’s internal air chamber and the EV sleeve act as a single air spring, slowly ramping up as you compress through the bike’s travel. At that 70% mark, a slide bushing inside the shock closes off the EV chamber, isolating the much smaller internal air chamber. This allows for a much more progressive air chamber, allowing the shock to ramp up in that last 30% of the suspension’s travel and preventing you from bottoming out towards the end of the bike’s travel.

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Specialized Ride Dynamics—the group responsible for developing the Genie shock—called its sliding bushing technology Pneumatic Spring Assist. The technology’s capabilities extend far beyond this shock, as outlined in this patent filed last year.

The Specialized Ride Dynamics team tested a wide variety of build options using early versions of the Genie shock before reaching a decision on factors such as the transfer point between large and small air volumes and whether or not to build the shock on a piggyback platform. Ultimately, they chose the Float as the basis for the technology, as any added benefit from the extra oil volume in a piggyback shock felt insignificant compared to the gains from the increased air volume. Fortunately, the Float is also a widely available shock with widespread parts availability, so spare parts for any necessary maintenance are easy to find.

While this clever technology allows the Genie shock to optimize performance for the Stumpjumper 15’s kinematics, it’s not like the bike can’t work with other, more typical shocks. I had the opportunity to test the bike back-to-back with the Genie and other off-the-shelf offerings, and while the custom shock seemed better suited, the stock options worked quite well.

Construction kits

All carbon, all the same layup, but with plenty of component differences to differentiate the build levels. The S-Works frame differs slightly in the use of a carbon fiber rocker link to save weight, but otherwise the frames are the same across the lineup. Every bike except the Öhlins build comes with a Genie shock.

Driving impressions

For the past few months, the Stumpjumper has been my primary bike for everyday fast laps and longer rides. That says something about how much I’ve enjoyed the bike so far, but it also speaks to the adjustability of the platform. The built-in geometry and suspension tweaks can fundamentally change the bike’s character, from a sharp-feeling trail bike to a downhill slugger, all within the parameters of the stock components. In terms of geometry, I find the stock position works best for me and my riding terrain. The 64.5° head angle steers intuitively on a wide variety of trails and still feels confident on really steep terrain. This is helped by the generous stack height, which keeps you in a strong, upright position with a nice amount of weight through the handlebars. My only gripe is the seat tube angle, which feels a bit too slack for me. This is likely due to my fairly tall seat height and the slacker actual seat tube angle.

I had the previous Alloy Stumpjumper EVO for years and I still remember many good rides on that bike. This one is better, especially in the bump-absorption department. The geometry between the two is quite similar, but the Stumpjumper 15’s ability to remain composed over very rough terrain is truly impressive. It also generates a surprising amount of traction for a 145mm travel bike, rivaling the longest-travel bikes in my garage. While the suspension feels quite active, I never found it to be floppy or vague under pumping scenarios – it simply moves around more than you might initially expect. For those who want the feel of a smaller bike, it’s as simple as adding more spacers to the shock’s Extra Volume chamber and setting the air pressure.

This past weekend I went on a ride that might just about highlight the Stumpy’s comfort, capability, and solid one-bike-ness. With about 95 miles and 18,000 feet of climbing, it was one of the biggest rides I’ve done in a while, and I feel like I picked the perfect bike for the job. There were no leisurely descents on the map, each with its own character and terrain differences. With the bike in its stock geometry setting, with 1 spacer in the shock, it felt like a good enough bike to hit some serious ground running, while remaining efficient enough not to add any extra work throughout the day. The casual stats drop isn’t so much to inflate my fragile ego, but to illustrate the versatile nature of the Stumpjumper—the ride felt comfortable and fun all day long. It’s worth mentioning that I experimented with the easy-to-reach lockout switch on a few fire road climbs, but ultimately preferred climbing with the shock open.

I have many more thoughts on this bike, but I’ll try to save most of them for the full review. Stay tuned, because this bike will definitely see many permutations as I continue to play with the setup and adjustments.