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Features of the frame

Things here look pretty similar to last-gen EVOs, with squeeze cups on the headset that allow ±1° of head angle adjustment, high/low chip flipping to change bottom bracket height and head tube/seat tube angle , and an aftermarket rocker link that lets you run a different size rear wheel. The last item only applies to bikes size S3 and larger, as the S1 and S2 options are mixed wheel only.

The Stumpjumper features SWAT 4.0, Specialized’s most advanced storage solution to date. First seen on the Epic 8, this latest iteration of the SWAT eschews any redundant frame-mounted hardware, and instead the hatch door interacts directly with the frame’s carbon, providing a tight fit, long life, and a great weather seal.

One new detail on the Stumpy that’s sure to cause some trouble is the elimination of mechanical drivetrain cable routing—this bike is wireless shifting only. 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 to mount the rear brake, which is a little surprising given the fact that almost all Stumpjumper builds come with SRAM Maven brakes – they can offer plenty of power on a smaller 180mm rotor. However, riding them with 200s front and rear never felt excessive 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 can be varied 1° in either direction from the standard position of 64.5°, via a set of easily replaceable cups that come with the frame. The reversible chainring chip allows the rider to raise or lower the bottom bracket height by 7mm while changing the head and seat angles by 0.5°. All of this adds up to a very wide range of adjustment, so for now I’ll stick with the standard values ​​that refer to average head angle and high flip chip position.

As mentioned above, the new Stumpjumper’s head angle is 64.5° – plenty of slack for just about anything, while still maintaining nimble handling on flatter corners. The effective seat angle at all sizes falls right around 77°, although the actual angle the seat tube throws is less than that figure, landing 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 30mm. Stack heights are very tall for a Specialized, with head length increasing significantly on larger bikes.

Bottom bracket drop is 38mm on all but the S1 bike, which measures 41mm. Chainstay lengths vary across the range, with lengths across all six sizes as follows: 430mm, 432mm, 435mm, 435mm, 445mm, 445mm. Again, some of these numbers may be modifiable by the end user, with different possible results as one experiments with the combinations.

Suspension design

In many ways it’s a familiar story, but the characters involved have evolved slightly to allow for a different outcome. Our protagonist – the damper – is the most significantly changed element in the game here, with some new technology allowing for very linear kinematics.

We learned a lot from developing the Levo SL in terms of percentage leverage. By moving to a slightly lower starting point and slightly less progression than our previous bikes, we saw improvements in consistency and control of ride feel throughout the range of motion, regardless of shock type. It also helped reduce the shock pressure a little and brought a little more ease to the shock setup process. Of course, the SL was developed around stock shocks without the Genie technology having been invented at this point. As we went into the Stumpjumper 15, we wanted to bring those features again, regardless of shock type, 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 percentage works great with stock shocks and also really helps highlight what the Genie brings to the table. We don’t need more early-stroke progression with the extra volume, and the adjustable secondary spring ramp is extra insurance for all riders looking for maximum support later in the travel. —Steve Saletnick

The genie shock

Given the linear nature of the Stumpjumper 15, it may seem necessary to apply a fairly progressive spring rate to protect the bike from sharp and frequent bottoming. 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 percentage. The first key element here is the shock’s massive air volume. This accounts for the beer can-sized outer air envelope called the Extra Volume (EV) chamber. For the first 70% of travel, the shock’s internal air chamber and EV sleeve act as a single air spring that slowly increases as you compress through the bike’s stroke. At this 70% mark, a sliding sleeve in the shock closes off the EV chamber, isolating the much smaller internal air chamber. This makes for a much more progressive air chamber, allowing the shock to ramp up in the last 30% of the travel and keeping you from leaking at the end of the travel.

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Specialized Ride Dynamics—the group responsible for developing the Genie shock—called this sliding sleeve technology Pneumatic Spring Assist. The possibilities this technology unlocks 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 with early versions of the Genie shock to decide on factors such as the transfer point between high and low air volume and whether to build the shock on a piggyback platform. In the end, they chose Float as the basis for the technology because any added benefit from the extra oil volume in the rebound damper felt insignificant compared to the gains from the increased air volume. Fortunately, Float is also a widely available shock with a huge parts availability, so replacement parts for any service required will be 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 doesn’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 while the custom shock seemed more appropriate, the stock options performed quite well.

Building kits

All carbon, all with the same layout, but with many differences in parts to differentiate the different 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 range. Every bike except the Öhlins build comes with a Genie shock.

Driving impressions

For the past few months, the Stumpjumper has been my go-to ride for daily hot laps and longer rides. That’s indicative of how much I’ve enjoyed the bike so far, but it also speaks to the adaptability of the platform. Baked-in geometry and suspension tweaks can fundamentally change a bike’s character, taking it from a sharp trail-feeling bike to a fast descent, all within the parameters of stock components. In terms of geometry, I find the stock position to be 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 confident on very steep terrain. This is aided by the large stack height, which keeps you in a stable upright position with good weight through the bars. My only gripe is with the seat tube angle, which feels a touch too slack for me. This is probably due to my fairly tall seat height and the slacker actual seat tube angle.

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

Last weekend I went for a ride that might just highlight the Stumpy’s comfort, capability and solid one-bike capability. At about 95 miles and 18,000 feet of climbing, it was one of the biggest rides I’ve done recently, 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 in a standard geometry setup, with 1 spacer in the shock, it felt like enough of a bike to hit some serious marks on the road, while remaining efficient enough to not add extra work during the day. The random stat drop isn’t so much to inflate my puny ego as to illustrate the Stumpjumper’s well-rounded nature—the ride felt comfortable and fun all day long. It’s worth noting that I played around with the easy-access lockout switch on a few fire road climbs, but ended up preferring the open shock climb.

I have a lot more thoughts on this bike, but I’ll try to save most of them for the full review. Stay tuned for this as this bike will certainly see a lot of permutations as I continue to play around with the settings and adjustments.