There's plenty of buzz surrounding Trek's new Session 29 (and for good reason), but the new Session 27.5 shouldn't be overlooked. After all, it's already garnered one World Cup DH victory under Rachel Atherton this season, and the updates should help to maintain its race-winning ways.
The new Session is longer, lower, and slacker, a now familiar refrain these days, and the carbon frame's design has been changed in order to eke out even more stiffness.
Trek Session 9.9 27.5 Details
• Travel: 210mm
• Full OCLV carbon fiber frame
• 62.1° - 64.4° head angle
• 157 x 12mm rear spacing
• Sizes: S, M, L, XL
• Price: $4,000 USD (frame and shock only), $8,000 complete.
• Available: August / September
Increasing the Session's stiffness was high on Trek's priority list, especially at the head tube and bottom bracket area.
The shock is now secured to the downtube rather than using the Full Floater design seen on the previous model.
The rear shock is now fixed to the downtube, similar to the design of the Slash 29
. According to Trek, advances in shock technology meant that the Full Floater design was no longer necessary to achieve the suspension feel they wanted. Trek worked closely with Fox on tuning the air-sprung Float X2 that the Session is spec'd with, but the bike's kinematics also allow a coil sprung shock to work without any trouble.
Overall, Trek claims that the new frame is 11% stiffer, with the bottom bracket seeing a 19% jump in stiffness, and the head tube stiffness increasing by 10%. Those are some significant changes, especially considering that the prior model wasn't exactly a wet noodle out on the track, but Trek wanted to create an even stiffer bike, one that could provide the cornering precision needed by elite DH racers.
There's plenty of clearance for meaty DH tires.
Bontrager are working on a hub that takes advantage of the extra space created by running a 7-speed drivetrain, pushing the hub flanges out for additional wheel stiffness.
Session 27.5 Geometry
The Session's reach has grown by approximately 20 millimeters, up to 445mm for a size large, and the bottom bracket height has dropped 6 millimeters, down to 349mm. The stock head angle now sits at 63°, but it's possible to go even slacker thanks to the headset cups that Trek provides. Those cups can be installed to change the head angle by 1° in either direction, and combined with the adjustments provided by the mino-link chip on the seatstay it's possible to create a super-slack 62.1° head angle, or steepen it all the way to up to 64.4°.