Does the Specialized’s New Stumpjumper and Its Genie Shock Change Trail Bikes Forever?

Specialized’s Stumpjumper is iconic. As the first production mountain bike, the Stumpjumper started a revolution in cycling when it debuted in 1981. As mountain biking road bike reviews 2024 developed and progressed over the decades, the Stumpjumper changed along with it. Specialized reinvented the Stumpjumper many times with different materials, new wheel sizes, disc brakes, and front and rear suspension to meet mountain bikers’ riding wants and needs.

Today, we see the launch of the latest generation of Stumpjumper, featuring an interesting new shock technology called Genie. By Specialized’s count, this new bike is the fifteenth generation of the full-suspension Stumpjumper platform (hence, it is dubbed Stumpjumper 15). The new bike is the best and most capable Stumpjumper the Morgan Hill, California-based brand ever produced.

It’s not immediately apparent, but something interesting is happening inside the new Stumpjumper’s shock. As Specialized states in the bike’s press kit, “Compared to other air shocks on the market, Genie allows for a lower spring rate earlier in the stroke, with a higher ramp later in the ending stroke.”

It attains this with a custom two-stage air spring developed in-house at Specialized. While Fox manufactures the shock, Specialized has patents pending on this system. This allows Specialized to potentially have the Genie spring built into any brand’s air shock.

Specialized isn’t the first to tinker with a multi-stage air spring. Trek’s DRCV (dual rate control valve) from more than a decade ago was a two-stage air spring built into some shocks and even a few forks. But the DRCV air spring volume was initially smaller before switching to a larger-volume air spring partway through the stroke: Genie is exactly the opposite.

For the first 70 percent of the shock’s travel, the Genie air spring consists of the volume inside the main air chamber plus the air sleeve volume surrounding the shock body. This air sleeve is also referred to as the XV (eXtra Volume) sleeve.

At 70 percent travel, a ring on the air piston blocks off the ports that allow the main air chamber to communicate with the sleeve’s air chamber, reducing air volume to only what remains in the eyelet.

And…that’s really it. The Genie’s air spring volume is extra-extra-large for this first 70 percent of travel but reduces to that of a standard air shock for the last 30-percent.

For this generation, Specialized not only made a new bike, but the brand also reoriented its trail bike lineup. The outgoing Stumpjumper line consisted of two bikes: the Stumpjumper with 130mm rear travel (with a single pivot/flex stay design) mated to a 140mm fork and the Stumpjumper Evo with 150mm rear travel (using a four-bar Horst Link design) and a 160mm fork.

The new Stumpjumper 15 has 145mm of rear travel via Specialized’s signature four-bar Horst Link system, mated to a 150mm fork. This model supplants the 130/140mm Stumpjumper and the 150/160mm SJ Evo.

“The goal was to take the best attributes of Stumpjumper (snappy and nimble) and Stumpjumper Evo (capable and adjustable) into one platform that catered to a wider range of riding styles and terrain,” said Todd Cannatelli, Specialized’s mountain program manager.

And since the new Stumpjumper has no weird standards, this bike will be easy to live with for a long time. Even if the future reveals some huge flaw with the Genie shock (I don’t see that happening, but who knows?) it has standard dimensions and mounting eyelets. So, owners can easily source a different shock for this frame.

I’m annoyed at Specialized because the Stumpjumper 15 is so well executed that it’s giving me nothing to complain about. All I got is that the textured finish honestly looks like there was an error when the painter tried to apply the clear coat.

Is the new Stumpjumper 15 with Genie the best trail bike available today? I don’t think one needs to try hard to make that case. This bike is dialed. But there are many great trail bikes on the market from brands big and small. I could list a dozen or more other trail bikes I’d happily ride. However, if you forced me to pick a single bike today, I’d go with the new Stumpy.