These aren’t spy photos. Not prototypes. Come this September, not one, but two new Trek Session 9.9s will hit the market, ready to descend a World Cup downhill course near you. Both of them feature new geometry and new linkage. Both of them include some fancy new suspension bits and design updates. But one of them will be descending at a widely believed internet-based rumor of 2.2 to 2.7 seconds faster than the other.
When the first experimental 29-inch downhill bikes surfaced nearly a decade ago, they were way ahead of their time. Wheels and tires weren't able to keep up, and today's breed of long-travel trail 29ers hadn't yet convinced the world of what big wheels were capable of. Trek was one of a handful of brands that ventured a few prototypes over the years, but none were quite ready to be released into the wild. By all indications, this one is.
Many of the refinements made to the 2018 Trek Session 9.9 might get buried under the heap of hype around the 29-inch model. But the 27.5-inch version isn't going anywhere, and Trek still expects it to be the go-to choice for most riders. One update shared between both bikes is the new Fox Float X2 rear shock. Trek kept a close eye over Fox’s shoulder while developing the Session, harmonizing the frame with the X2's new capabilities. Its damping circuits allowed Trek to design their linkage with a lower leverage ratio and longer shock stroke. The damper can now play a bigger role in supporting the rider, allowing for more tunability.
Tunability is the main reason Trek opted for a fixed lower shock mount on the new Session. Their signature Full Floater shock mount offered a dimension of adjustability that can now be left to the shock itself. Plus, the new design makes for a stiffer, stronger and lighter frame. Tunability was also the motivation for optimizing the Session for an air spring over a coil. You can still run a coil if you want, but given how much more plushness the new technology allows, an air shock's exclusive ability to adjust spring volume and pressure comes with little sacrifice, and is well worth taking advantage of.
The Session 9.9 got some significant geometry updates, a few of which are up to you. You’ll still get Trek’s Mino Link flip chips, so you can dial in a half degree of head angle and 8 millimeters of bottom-bracket height. And each bike and frame will ship with traditional headset cups installed, but you’ll get a set of fixed-angle 1-degree offset cups on the side. Fixed-angle, meaning no spherical interface, no pinch bolts, just creak-free customization. Out of the box, the new Session 27.5 head angle rests about a half degree slacker than the current version at at 63 degrees. The bottom bracket got 10 millimeters lower and the cockpit gained 20 millimeters. Both frames carry over the 210-millimeter rear travel of the current Session.
Comparatively, the 29-inch version has the extra chainstay length and bottom-bracket drop you'd expect from bigger wheels, and the head angle is nearly a degree slacker. After all, this new beast's only purpose is speed. It’s aimed at a narrow niche within the already narrow niche of elite downhill racing. Therefore, while the 27.5 Session 9.9 will be available as either an $8,000 complete or a $4,000 frame, the Session 29 will only be available as a frame kit. That kit will include the Session 29 OCLV frame, Float X2 rear shock, and straight and 1-degree-offset headset cups. Oh, and an air-sprung 29-inch 203mm Fox 40 RC2 fork. Because why would you choose anything else? That package will run you a cool $5,000.
The Trek Session 29 will be produced in limited numbers, but not because of lack of commitment. Trek and Fox went all-in on design and quality, but this bike is not for everyone, and there’s no telling if the DH community will embrace it. We’ll all be on the edge of our seats, watching the clock to find out.