2015 Trek Session DH 27.5 vs 2017 Specialized Demo Alloy
The LONG is the Specialized Demo Alloy size closest to your L Trek Session DH 27.5. 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 Alloy
Compared with the Trek Session DH 27.5 in L, the Specialized Demo Alloy in LONG places the top of the head tube 11 mm higher and 8 mm further forward, relative to the bottom bracket.
- Frame stack
- +11 mm
- Higher front end
- Frame reach
- +8 mm
- Longer frame reach
- Wheelbase
- −1 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 DH 27.5 numbers we have for size L are missing the seat angle. The numbers below still compare.
Geometry side by side
| Measurement | Trek Session DH 27.5 L | Specialized Demo Alloy LONG | Difference |
|---|---|---|---|
| Reach | 432 | 440mm | +8 mm |
| Stack | 603 | 614mm | +11 mm |
| Head tube angle | 64.2° | 63.5° | −0.7° |
| Effective top tube | 614 | 616mm | +2 mm |
| Chainstay length | 443 | 430mm | −13 mm |
| Wheelbase | 1229 | 1228mm | −1 mm |
| BB drop | 14 | 12mm | −2 mm |
| BB height | 364 | 342mm | −22 mm |
| Standover | 790 | 698mm | −92 mm |
| Seat tube length | 390 | 367mm | −23 mm |
| Head tube length | 115 | 105mm | −10 mm |
| Seat tube angle | not listed | 74° |
Differences are the Specialized Demo Alloy minus the Trek Session DH 27.5. Full charts: 2015 Trek Session DH 27.5, 2017 Specialized Demo Alloy.
Where each sits in its class
Trek Session DH 27.5Specialized Demo Alloy
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 DH 27.588 DH 27.5 | Specialized Demo Alloy8 Alloy |
|---|---|---|
| Frame | Trek Alpha Platinum | not listed |
| Fork | RockShox BoXXer | not listed |
| Shifter | SRAM X9 | not listed |
| Derailleur | SRAM X-0 | not listed |
| Cassette | SRAM PG-1050 | not listed |
| Chain | KMC X10 | not listed |
| Crankset | TruVativ Descendant DH | not listed |
| Pedals | Wellgo MG-1 | not listed |
| Wheelset | DT Swiss FR2150 | not listed |
| Tire | Bontrager G4 Team Issue | not listed |
| Brake | Avid Code | not listed |
| Handlebar | Bontrager Rhythm Elite | not listed |
| Stem | Bontrager Rhythm | not listed |
| Headset | FSA NO.57E | not listed |
| Seatpost | Bontrager Rhythm Elite | not listed |
| Saddle | Bontrager Evoke 2 | not listed |
| Rear shock | not listed | Öhlins TTX |
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