Specialized Stumpjumper Comp Alloy: First Ride Review – Travis Engel | The Radavist | A group of individuals who share a love of cycling and the outdoors.

The new Specialized Stumpjumper didn’t exactly get a refresh. It got a reboot. It now has more in common with the critically acclaimed Stumpjumper Evo than the mild-mannered Stumpy we once knew. And its Genie shock promises unprecedented dimensions of tunability. But at first, the carbon-frame-only update came with an electronic-drivetrain-only twist. That’s why, when Travis heard an aluminum version was coming, he signed up.

I couldn’t have rolled my eyes harder when I saw that Specialized chose the tag line, “One Bike to Rule All Trails.” for July’s launch of the fifteenth-generation Stumpjumper. Never mind that Sauron’s words were originally spoken in the spirit of subjugation and malice. The phrase has been co-opted to death in pretty much every product category you can think of. Trucks, hats, knives, cookies. Name an object, and someone invoked Tolkien’s text to praise it. When it comes to bikes, though, Specialized may actually be the most high-profile adopter of The Ring Verse. But not for the Stumpjumper.

Originally, they used it for the Tarmac endurance road bike. I guess that’s why they went for the slightly clumsier “to Rule All Trails” instead of “to Rule Them All.” I figured there must be a better catchphrase … But then I rode it, and I gotta say, the new Stumpy probably deserves this cliche more than any other bike I’ve ridden. Especially now that there’s an aluminum option with rear-derailleur cable routing.

Infamously, the carbon Stumpjumper 15 accepts wireless derailleurs only. That doesn’t matter to me, since I’m a SRAM Transmission lifer. And I suspect the same is true of most riders spending $5,500 or more on a Stumpjumper. I don’t know if Specialized eliminated shift-cable routing for aesthetics, cost, or shock value, but I don’t think it really matters.

I’ve probably already talked about it too much. If the trend continues, as the launch of the also-wireless Santa Cruz Hightower and Bronson CC frames indicates it might, it’ll likely be localized to the ultra-high-end. After all, the lower-level-carbon Hightower and Bronson C frames will have mechanical routing. Don’t get me wrong, I’m totally against electronic-only frames. But I’m totally not worried. I’d rather talk about everything else going on with the new alloy Stumpjumper.

Specialized Stumpjumper Comp Alloy Quick Hits

145 mm rear travel, 150 mm front
29” front and rear wheels except for smallest S1 and S2 sizes, which are mixed-wheel
Available in six frame sizes, S1 through S6 (essentially XS-XXL)
Unique “Genie” rear shock with larger air spring and mid-stroke tuneability
Other shocks (including coil) available on other builds
Includes multiple shock-tuning components, out of the box
Headset offers neutral, +1° and -1° positions
Features SWAT downtube storage and SWAT tool-equipped bottle cage
36.6 pounds (size S5 without pedals)
Available frame-only for $2,300
$4,500
Sold through Specialized dealers or at specialized.com

The new Specialized Stumpjumper swallowed up both the previous-generation Stumpjumper and its top-bunk-mate, the Stumpjumper Evo. The vanilla Stumpjumper used to be a lightweight 130 mm rear- / 140 mm front-travel trail bike whose flex-stay suspension almost seemed to have a foot in the XC category. The Stumpjumper Evo was a middleweight 150 / 150 mm trail bike whose adjustable geometry could out-slack even the heavyweight Enduro.

This new Specialized Stumpjumper leans much more towards the EVO, with the same head-tube angle, the same dimensions of frame adjustability, and very similar travel, wheelbase, and fit numbers. But it’s got a (slightly) lighter-weight frame, and most importantly, a fancy new rear shock.

Genie Shock

Whenever bike brands work with shock brands to create something new and unique, it rarely seems to last. Cannondale’s Dyad, Trek’s Thru-Shaft, and even Specialized’s Brain all eventually faded away. But I don’t picture the new Specialized Stumpjumper’s “Genie” shock disappearing unless something revolutionary takes its place.

Normally, volume spacers simply displace the empty space inside of an air spring. Late in the stroke, when that empty space is squeezed down to the minimum, the reduction in volume means the air is more tightly compressed, and more force is required to reach bottom-out. And bottom-out is pretty much all that volume spacers affect. Although they might allow you to take a different approach to shock pressure, they won’t, on their own, make the mid-stroke any more or less supportive.

That’s what’s different about Genie. It features an especially large air chamber, which can mimic the supple early and mid-stroke feel of a coil shock. But that large air chamber includes a partially walled-off section that surrounds the more traditional-sized central air chamber. About 70% through the travel, a sleeve attached to the end of the piston shuts off the ports into that second chamber, leaving only what’s left of the main chamber to control the rest of the stroke.

That means you can get the linear feel of a coil spring with the bottom-out resistance of an air spring. But it also means you can individually adjust each chamber’s volume. If you want to maximize that coil-like feel, leave that outer chamber more empty. But if you want the mid-stroke support of an air shock, you can add volume spacers. And independently, you can add traditional volume spacers to control late-stroke support.

Interestingly, Specialized also includes a 2.5mm travel-reduction plate that fits the Genie and some other Fox shocks. Worth noting, because bike brands rarely want consumers messing with that stuff. But in the Stumpjumper’s case, you can drop it from 145 to about 140 mm. And I should mention that you can always just use a regular shock, either coil or air. There’s nothing proprietary about the Genie’s shock’s fitment, and the bike doesn’t rely on its features to work properly.

Specialized Stumpjumper Frame and Design Features

The theme of tunability carried over from the Stumpjumper Evo is all over the frame itself. There’s a geometry flip-chip on the chainstay that does all the normal stuff. About a half-degree angle change and 7mm of bottom bracket drop. Specialized offers an aftermarket swing link for those who want to go mixed-wheel, though the smallest two sizes come mixed-wheel out of the box. That would be the S1 and S2 sizes. Specialized uses that naming convention on most of their mountain bikes because they believe bike size isn’t like pants size. You choose the one you want, not the one that “fits.” There are traditional 25-30 mm gaps between the six sizes, so you’ve got a lot of choices.

Up front, Specialized has an easy-to-install +1° or -1° headset cup. It’s keyed so it stays straight and doesn’t need a special tool to be pressed in. I actually brought it with me on my first couple of rides so I could go back and forth and decide the setting I liked. It’s a smart feature on a bike full of smart features.

One of which is something I don’t remember having seen before. Specialized is offering a lifetime of free replacement pivot hardware for the original owner. Ibis offers replacement lower clevises and bushings, but not the upper pivots. Kinda neat. And of course, the SWAT Box is there on the downtube, though it didn’t get the refined latch that the carbon-frame SWAT boxes are getting. An underappreciated perk of downtube storage is that it allows brands to put user-accessible cable tethers inside the wall of the frame to keep them from rattling.

Outside the downtube is a pretty robust plastic-core rubber frame protector that bolts on instead of sticking on. And finally, I like the 35mm seat tube diameter. And I like that the 35mm seat post also has the oversized 28.2 mm upper compared to 26 mm for normal-sized posts. I just wish X-Fusion could make one with more than 190 mm of drop, but that’s a topic for spec.

Spec and Value

I tested the $4,500 Comp Alloy model, which gets a full SLX drivetrain, TRP Trail Evo brakes, a Fox Rhythm 36 fork, and a Performance-level Genie shock. I liked that Specialized specced the very soft T9-compound tire up front and the moderately soft T7 compound in the rear. And the Grid casing is a good light heavy tire or heavy light tire depending on what you’re used to. Not sure I liked that the S4 through S6 have a mandatory 200 mm rear rotor, with only the S1 through S3 frames accepting a 180. I got used to it, but if I were on one of the SRAM Maven-equipped models, it’d have been way too locky in the rear.

Only three models across the whole Stumpjumper lineup don’t get the Genie shock. Two of them are coil-shock builds, and the other is the entry-level build with a basic X-Fusion shock. It’s admirable that Specialized went down to $3,000, but amid other important downgrades, its “normal” rear shock has me thinking the Ibis Ripmo AF or Marin Alpine Trail stand out more in the value department (when comparing non-consumer-direct bikes).

Above it, there’s the $5,500 Fox Coil Alloy, but its bigger 160 mm Fox 38 fork kinda puts it in another category. For the same price, there’s also the carbon-fiber Comp build, with the new SRAM S1000 Transmission drivetrain. We haven’t yet reviewed S1000, though. And it’s not specced on enough bikes to compare value. If carbon and Transmission are on your must-have list, $5,500 is likely what you’re going to spend for any brick-and-mortar retail brand. But not only does the Comp Alloy best nail the bang / buck sweet spot, but It best suits this generation Stumpjumper’s new identity.

Climbing

The previous-generation Stumpjumper was a pretty outstanding climber and a pretty ok descender. This Stumpjumper is the opposite. The focus is the downhill, but it’ll get the job done on the uphill. The geometry is what I’d call “relaxed.” Specialized, unfortunately, still slackens seat angles on larger sizes, but I was able to get comfortable on my S5 (XL) frame by slamming the saddle forward. Presumably, shorter riders can get by if they slam theirs backward. The frame stack and bar height are on the tall side, which kept me from ever feeling like there was any rush to get to the top of the hill.

And I rode it in the default “high” geo setting for nearly the whole time. Kudos to Specialized here. Often, a long-travel bike’s high setting is useless. It goes against the spirit of the category. Instead, Specialized, Evil, and recently, YT, tend to do what some would call “low” and “extra low” settings. The “low” setting offers stability with minimal compromise, while the “extra low” setting offers more stability with more compromise. In my one and only “extra-low” test lap, I was draggin’ heel, even crossing the occasional fire-road rut. It was fun as long as I didn’t have to pedal. Color me jealous if that’s how your trails work, but it was too low for me.

Thankfully, I’d say the suspension was on the supportive side, especially given the travel. Supportive but not very nuanced. By that, I mean the linkage isn’t doing anything fancy to track the ground when there’s a lot of force going through the drivetrain. I’m a little spoiled, ‘cause the similar-travel Ibis Ripmo I just tested struck a perfect balance of spunk and sensitivity. On the Stumpjumper, I occasionally managed to time a pedal stroke and a rock shelf to meet each other at the exact wrong moment, and I would get a little hung up. Still, it beats the alternative. I wouldn’t want a bike like this to feel mushy. Plus, for lockout fans out there, I think the firm pedaling platform made for an even firmer locked-out setting. It puts it in “heavy hardtail mode,” and I mean that in a good way.

How I set up the Genie rear shock played a role here, too. I ended up riding the Stumpjumper with a slightly firmer preload than usual, which played well with its supportive pedaling characteristics. But to explain how I got there, we’d have to talk about descending.

Descending

Specialized makes some lofty claims about what this shock can do. Again, it’s built around a very large-volume air can that gets walled off in the last 30% of the stroke, so the smaller remaining volume can add bottom-out resistance. That larger volume for the first 70% of the stroke means the suspension will yield measurably more travel than a traditional shock when hit with the same impact.

I won’t bore you with the graphs, but according to Specialized, “A 1,080-Newton impact force results in 100 mm of travel on the Stumpjumper 15, whereas the Stumpjumper EVO only uses 86 mm of travel to absorb the same force.” This sounds like engineer-speak that the average rider won’t feel on the trail. But I guarantee, you will feel it on the trail.

It was immediate. I won’t quite say that it felt like a coil shock. There still is a tiny bit of stiction that results from an air shock’s increased seal drag. But this bike absolutely floated through high-speed choppy sections. Specialized puts that increased travel-per-bump performance on par with the 170 mm travel Enduro. I’d say that’s about right.

Despite having “only” 145 mm of travel, the Specialized Stumpjumper felt utterly bottomless. And that soft mid-stroke transitioned seamlessly to the chewy late-stroke. The bottom-out resistance started earlier and easier than it would if I were simply relying on volume spacers. It was a true magic carpet ride. But it didn’t take long before I started feeling the downsides.

The rear wheel and the ground hugged one another with such tenacity that I had a hard time pulling the two apart. I would stop short of calling it “mushy,” at least in the sense of the word as I’d used it before. That late-stroke support meant the “mush” would meet an earlier end than if I were just riding a normal shock I’d set up too soft. But still, the bike was very businesslike. It wanted to maintain traction, control, and contact with the trail. Thankfully, that’s what the volume spacers were for.

I added one, then three of the clever clip-in spacers to the Genie’s relatively easy-to-access outer chamber. You need a strap wrench only if you want to change the late-stroke volume spacer or travel reducer. Once I got back up to pressure, a fun-first alter-ego emerged from within the Specialized Stumpjumper. It was a lot like the Reeb Steezl or Ibis Ripmo, where it felt like a 145(ish) mm bike in the rough stuff, but could pop around like it had less travel. I left it that way for a couple rides, until I realized something. The bike was great in that configuration. It just wasn’t necessarily anything all that special.

So, I went back into the shock and removed all those outermost volume spacers that I’d installed, and then increased my preload. For years, I’ve set up my rear shock to have pretty deep sag. When I’m leaning forward on the downhills, I’m not putting enough energy through the shock. So, to get the rear wheel to react how I want, I usually set sag around 33%. But with Genie, I realized I could approach it differently. I increased preload so I was a hair under 30% sag, and something cool happened. It wasn’t the cloud I felt on my first run, but it absolutely did absorb hard hits better than any 145(ish) mm bike I’d ever ridden. And at the same time, I got most of that responsiveness back. I was in much more control through high-speed rough sections.

Sometimes, when I see raw footage of pro enduro racers careening masterfully over a chaotic root section, I feel like we’re in two different sports. You can tell that they’re on exactly the line they wanted to be, but meanwhile, there’s a rapid-fire “thud, thud-thud, thud, thud-thud-thud,” as the bike is getting mercilessly pounded. And the rider is totally unbothered. Relaxed, even. The way that looks and sounds is the way the new Specialized Stumpjumper feels. And the best part is that the Genie shock allows you to click all of its many virtual dials one way or another to get it to suit your evolving needs.

Like, if the bump-absorption were to help me get comfortable at higher speeds in rougher sections, maybe I’d need to add a bit of mid-stroke support with one or two more spacers. This bike would allow me to get that support with much less of the compromise I’d make if I just added air pressure. It’s a perfect next step in the legacy of adjustability introduced on the Stumpjumper Evo.

That legacy is also present in the return of the angle-adjust headset. Wolf Tooth has made an amazing semi-universal option that eliminates the increase in height and creakyness of earlier attempts. But it needs to be pressed in (carefully and straightly), and of course, purchased aftermarket. That Specialized includes an angle-adjust feature on the Stumpjumper is a huge value-add. That it can be installed with no more than a 4 mm hex wrench is a very open invitation to think about how you would make your Stumpjumper your Stumpjumper.

I spent time in the slacker and steeper settings, but for my needs, the middle setting was ideal. I liked the thought of having a 63.5-degree-head-tube trail bike. And if I were one of those freaks who needed the extra-low bottom-bracket setting, maybe those two options would have paired nicely. But it got unwieldy in the jibby little moderate-speed sections where I liked the Stumpjumper most. In fact, I even made it slightly more jibby with an underused feature on some Fox shocks.

This little spacer doesn’t shorten the shock eye-to-eye length. Just the stroke length. I can’t ramble for too long about the nuances of a 5 mm reduction in travel, but it helped tie the Stumpjumper to its trail-bike roots. And because of the way the large-volume air spring worked so well with my slightly shallower sag setting, the bike still had phenomenal bump absorption. It just suited my trails the best that way.

I think that’s the standout feature on the new Stumpy. It can be tailored for pretty much any rider and any terrain. That sort of approach to bike design can often feel kinda hacky. Like, as if the brand can’t commit to a singular vision, so they try to make a Swiss-army bike that doesn’t really excel in any one of its many forms. But the new Specialized Stumpjumper isn’t like over-forking an XC bike to make it a trail bike, or building a modular frame platform with potentially suboptimal geometry. Every combination of Stumpjumper settings is a reasonable solution for someone. And those combinations are easy to find your way to through slow experimentation. Ironically, I think it’s a perfect solution for the choice paralysis often facing today’s bike buyers. There are so many good choices out there, but you only get to make that choice once. The Stumpjumper allows you to keep making choices for years.

Hopefully, though, the new Specialized Stumpjumper won’t utterly consume you, cursing you with unnaturally long life until it inevitably tires of you and seeks a new bearer only to set into motion a chain of events that lead to its own destruction. But it might rule all trails, which is pretty cool.

Pros

Rear shock offers nearly coil-like bump sensitivity
Easy to tune the bike to have a more traditional air-shock feel, or to go somewhere in between.
Simple head-angle adjustment
Actually has rear-derailleur cable routing
Six sizes and a wide fit range
Smart use of a flip-chip