Reframing Stumpjumper

Innovate or Die

We pour our heart and soul into every new bike we make. It’s a commitment to improving the ride we’ve been obsessed with since 1974. But some projects are special and some projects the stakes are simply higher. Take the most historic name in mountain biking, the bike that truly started it all. There’s the weight of history, responsibility to uphold a legacy, and an absolute demand to take trail riding to the next level. This is what awaits any team tasked with reinventing an entire class of bike. This is Stumpjumper. No pressure.

Reframing Stumpjumper

Innovate or Die

We pour our heart and soul into every new bike we make. It’s a commitment to improving the ride we’ve been obsessed with since 1974. But some projects are special and some projects the stakes are simply higher. Take the most historic name in mountain biking, the bike that truly started it all. There’s the weight of history, responsibility to uphold a legacy, and an absolute demand to take trail riding to the next level. This is what awaits any team tasked with reinventing an entire class of bike. This is Stumpjumper. No pressure.

The “Ultimate Trail Bike” is no idle slogan. For decades, Stumpjumper has set the bar as the most versatile and capable trail bike on the planet. To take everything that the Stumpjumper is the benchmark — effortless control on flowing singletrack, blistering speed through steep, chunky terrain, and confidence to huck off blind drops — and raise the bar. To do that required us to create the lightest, most efficient, most capable trail bike we’ve ever made.

Simple right?

The “Ultimate Trail Bike” is no idle slogan. For decades, Stumpjumper has set the bar as the most versatile and capable trail bike on the planet. To take everything that the Stumpjumper is the benchmark — effortless control on flowing singletrack, blistering speed through steep, chunky terrain, and confidence to huck off blind drops — and raise the bar. To do that required us to create the lightest, most efficient, most capable trail bike we’ve ever made.

Simple right?

For this all-new Stumpjumper, it started with the bike’s backbone: the frame. Control, efficiency, durability, and weight savings are all born from the frame itself. Recent breakthroughs in our carbon lab resulted in a new understanding of how shape affects a frame’s performance. Shape, not material, determines the vast majority of a frame’s weight, stiffness, and durability. Thanks to the largest Finite Element Analysis study we have ever undertaken, we’ve optimized the dimensions and radii of the Stumpy’s frame tubes and their intersections, ensuring that every fiber of carbon is delivering the most strength and stiffness it possibly can. When every piece of carbon is truly pulling its own weight, “lazy” material that would otherwise hide in unoptimized corners is totally eliminated.

Small adjustments in shape make big differences in how a material performs. A great example of this is the shock mount at the top tube. By keeping the top tube “intact” \(rather than piercing and bending it to shroud the shock, like the previous Stumpjumper\), it’s more structurally sound and therefore more effective at bearing a load with less material. The flat sections of the shock mount likewise carry those loads more effectively than the curved shock mounts of the previous Stumpy. Together, this top tube/shock mount section is lighter and stiffer than its predecessor, without sacrificing durability.

Another example of how shape optimizes material use is the sidearm design. The asymmetric sidearm strut supports the shock link pivot, boosting stiffness by connecting rear end with front for a direct and integrated feel. The sidearm also prevents torsional loads from entering the top tube, which helps the bike track and handle with precision

A: The top tube is structurally optimized by retaining its tubular integrity, while the flat sections of the shock mount plates intelligently transfer loads to the robust sides of the top tube.

B: The sidearm strut supports the shock link pivot, boosting stiffness by connecting rear end with front for a direct and integrated feel.

While material shape delivers the vast majority of a frame’s performance, for a bike like the Stumpjumper we coaxed every last gram of performance out of the frame. That meant utilizing the strongest, most expensive carbon we’ve ever built a mountain bike with. We selected the optimal material for every layer of carbon, all chosen to deliver the maximum performance needed in that region of the frame. This — along with our careful study of shape — is what allowed us to achieve our rider-focused performance targets with the minimum amount of material.

Once the frame shape was finalized and material selection made, refinement of the layup schedule came from testing prototypes in the lab and on the trail. This process provided qualitative and quantitative feedback that illuminated how to make improvements in the layup. We revised the layup schedule, built another proto, and tested again. And again. The iteration loop continued for 203 days for the Stumpjumper, culminating at our goal of the lightest, best handling, most efficient 130/140mm travel trail bike we’ve ever created. Believe us when we say that there’s no lazy material loafing around in the Stumpy frame.

One of the frame’s biggest breakthroughs came from the Flex Stay, enabling us to remove the Horst link to save weight and increase durability while mimicking the four-bar FSR system perfectly. We can manipulate the carbon fiber seatstay’s stiffness to an incredible degree, all based on how we orient the carbon fiber. The result is a tube section that can flex vertically yet be incredibly stiff laterally, recreating a pivot with our Flex Stay.

This absolute obsession, these breakthroughs, and this attention to detail created a Stumpjumper chassis at just 2,420 grams \(size S-4\) — including paint, shock, assembly hardware, link, carbon extension, molded downtube and chainstay protectors, axle, and seat clamp. While it’s longer and slacker than the previous Stumpjumper, it’s more than 100 grams lighter. And we’ve done it while improving handling characteristics, pedaling efficiency, and toughness. See? Simple.

This absolute obsession, these breakthroughs, and this attention to detail created a Stumpjumper chassis at just 2,420 grams \(size S-4\) — including paint, shock, assembly hardware, link, carbon extension, molded downtube and chainstay protectors, axle, and seat clamp. While it’s longer and slacker than the previous Stumpjumper, it’s more than 100 grams lighter. And we’ve done it while improving handling characteristics, pedaling efficiency, and toughness. See? Simple.