2017 Trek Session AL 27.5 Frameset vs 2015 Specialized Demo
The M is the Specialized Demo size closest to your M Trek Session AL 27.5 Frameset. We match frame stack and reach. This is a geometry comparison, not a fit recommendation; stem, spacers, handlebars and saddle setup also affect your riding position.
What changes on the Specialized Demo
Compared with the Trek Session AL 27.5 Frameset in M, the Specialized Demo in M places the top of the head tube 10 mm higher and 11 mm further forward, relative to the bottom bracket.
- Frame stack
- +10 mm
- Higher front end
- Frame reach
- +11 mm
- Longer frame reach
- Wheelbase
- +2 mm
- About the same
- Head angle
- −0.7°
- Slacker: calmer steering
- Chainstays
- −13 mm
- Shorter: livelier
The two frames
We can't draw these frames yet. The Trek Session AL 27.5 Frameset numbers we have for size M are missing the seat angle. The numbers below still compare.
Geometry side by side
| Measurement | Trek Session AL 27.5 Frameset M | Specialized Demo M | Difference |
|---|---|---|---|
| Reach | 408 | 419mm | +11 mm |
| Stack | 603 | 613mm | +10 mm |
| Head tube angle | 64.2° | 63.5° | −0.7° |
| Effective top tube | 590 | 588mm | −2 mm |
| Chainstay length | 443 | 430mm | −13 mm |
| Wheelbase | 1205 | 1207mm | +2 mm |
| BB drop | -9 | not listed | |
| BB height | 364 | 347mm | −17 mm |
| Standover | 756 | 721mm | −35 mm |
| Seat tube length | 445 | 393mm | −52 mm |
| Head tube length | 150 | not listed | |
| Seat tube angle | not listed | 63° |
Differences are the Specialized Demo minus the Trek Session AL 27.5 Frameset. Full charts: 2017 Trek Session AL 27.5 Frameset, 2015 Specialized Demo.
Where each sits in its class
Trek Session AL 27.5 FramesetSpecialized Demo
Each bike is ranked against the other downhill bikes on Quiver, on frame geometry alone. Not your hand position or ride feel.
What each ships with
The stock build of each bike's first listed trim. Parts that match are dimmed.
| Part | Trek Session AL 27.5 FramesetAL 27.5 Frameset | Specialized Demo |
|---|---|---|
| Frame | Trek Alpha Platinum | not listed |
| Headset | FSA Orbit | not listed |
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