A 63.5-degree head tube angle? Yeah this thing's built to shred. But it's not just the geometry that makes it so capable. Oh no. The Stumpjumper EVO carbon 27.5 has been designed with one goal, to conquer the gnarliest of trails out there without a DH bike.
What exactly is the Evo for? Evo is for the shredders, the gnarliest trail riders who live for gravity riding. Big drops, huge kickers, rocks, roots; whatever you throw at it the Stumpjumper Evo can handle it. Evo uses the same style-specific sizing that's featured on the Demo. This sizing lets you choose the bike that fits the way you ride, not just by the seat tube measurement like with most bikes, and it narrows things down to two sizes; s2 and s3. These are longer, lower, slacker and have seat tube and head tube heights that allow you to choose the size that best suits your style and terrain.
The other design goal was simple - build the ultimate trail bike. One that feels telepathic. And it turns out that this feeling all comes down to stiffness. Think of it this way: when the frame's telling your hands one thing and your feet another your brain gets confused with the imbalance and the bike feels unstable. In order to fix this Specialized had to get to work on dialing-in the materials and shapes.
They started by creating their own mountain-specific stiffness test and then look at the layout with finite element analysis (fea) to see where they could get the biggest stiffness improvements. This led to a big discovery: the large and x-large frames needed more front-end stiffness while the smalls and mediums were just fine. They were able to create a frame design that was 20% more efficient. And in the end this proved to be one of the lightest trail frames on the market today.
When designing the frame with the stiffness targets being a main goal they developed a radical new sidearm design. The front-end and rear-end are connected at three points and the sidearm helps keep all these points super stiff and connected, all while taking about 100 grams out of the rear-end. More explicitly this minimizes frame flex when the rear suspension is active.
They continued down the suspension path with a custom rx trail tune on both the fork and rear shock. Suspension performance is highly dependent on frame wheel and rider size so they use their rx tune to get each bike to land in the middle of the adjustment spectrum and this gives you the biggest possible range to fine-tune your ride. Another focal point of the tune was matching the suspension characteristics between wheel sizes; they developed a specific rx tune for each platform. So no matter what wheel size you prefer you'll get perfectly linear suspension.
Steps were also taken to make this bike easy to live with. Threaded bottom brackets make a triumphant return and they've made room for up to a 2.8 tire. You're also free to run whatever aftermarket rear shock you want since using standard metric shocks. Specialized revamped the SWAT box too, making it sleeker, lighter and with more volume. And customization is furthered with a flip chip that lets you to dial-in your stumpy to your riding style. Switch it from high to low and it drops your bottom bracket 6mm and slackens the head tube by half-a-degree. Little details also jump out to surprise you like a newly designed ribbed chainstay protector that makes chain slap a thing of the past and nearly silences the drivetrain. Lastly cable routing couldn't be any easier on carbon models. Full tubes can be found throughout the carbon frame so all you have to do is push the cable and it'll come out the other end. No more lazy loop hidden stashes of magnets pokey spokes or pillows to cry in.