Ever had a ride that felt more like an experience than just a ride? Us, too, and we’ve been chasing that feeling ever since. With the Stumpjumper Expert 27.5, we’ve bottled up that feeling and put into a radical new frame design that’s so agile, lively, and in-tune with the trail, the bike feels like an extension of your body. Seriously, it’s going to make you rethink how a trail bike should ride. Our design goal for the new Stumpjumper 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, we had to get to work on dialing-in the materials, shapes, and the layout. We started by creating our own mountain-specific stiffness test, and then we looked at the layout with Finite Element Analysis (FEA) to see where we 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. We 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, we 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. We 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 we use our 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—we 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 we made room for up to a 2.8 tire. You’re also free to run whatever aftermarket rear shock you want, since we’re using standard metric shocks. We 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, we seriously couldn’t make cable routing 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. For the build, you get a solid components package with a full SRAM GX1 Eagle drivetrain, SRAM Guide R disc brakes, RockShox front and rear suspension (150/150mm of travel respectively), and Roval Traverse Carbon 27.5 wheels.