2017 Specialized Demo II Alloy vs 2015 Trek Session DH 27.5
The S is the Trek Session DH 27.5 size closest to your SHORT Specialized Demo II Alloy. 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 Trek Session DH 27.5
Compared with the Specialized Demo II Alloy in SHORT, the Trek Session DH 27.5 in S places the top of the head tube 11 mm lower and 6 mm further back, relative to the bottom bracket.
- Frame stack
- −11 mm
- Lower front end
- Frame reach
- −6 mm
- Shorter frame reach
- Wheelbase
- +2 mm
- About the same
- Head angle
- +0.7°
- Steeper: sharper steering
- Chainstays
- +13 mm
- Longer: more planted
The two frames
Only the Specialized Demo II Alloy is drawn. The Trek Session DH 27.5 numbers we have for size S are missing the seat angle.
Geometry side by side
| Measurement | Specialized Demo II Alloy SHORT | Trek Session DH 27.5 S | Difference |
|---|---|---|---|
| Reach | 395mm | 389 | −6 mm |
| Stack | 614mm | 603 | −11 mm |
| Head tube angle | 63.5° | 64.2° | +0.7° |
| Seat tube angle | 74° | not listed | |
| Effective top tube | 571mm | 570 | −1 mm |
| Chainstay length | 430mm | 443 | +13 mm |
| Wheelbase | 1183mm | 1185 | +2 mm |
| BB drop | 12mm | 14 | +2 mm |
| BB height | 342mm | 364 | +22 mm |
| Standover | 698mm | 810 | +112 mm |
| Seat tube length | 367mm | 390 | +23 mm |
| Head tube length | 105mm | 115 | +10 mm |
Differences are the Trek Session DH 27.5 minus the Specialized Demo II Alloy. Full charts: 2017 Specialized Demo II Alloy, 2015 Trek Session DH 27.5.
Where each sits in its class
Specialized Demo II AlloyTrek Session DH 27.5
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 | Specialized Demo II Alloy8 II Alloy | Trek Session DH 27.588 DH 27.5 |
|---|---|---|
| Fork | RockShox Boxxer Team | RockShox BoXXer |
| Rear shock | Öhlins TTX | not listed |
| Shifter | SRAM X9 | SRAM X9 |
| Derailleur | SRAM X0 | SRAM X-0 |
| Cassette | SRAM PG-1030 | SRAM PG-1050 |
| Chain | SRAM PC-1031 | KMC X10 |
| Crankset | SRAM X0 DH | TruVativ Descendant DH |
| Pedals | Specialized Bennies | Wellgo MG-1 |
| Tire | Specialized Slaughter, Specialized Butcher | Bontrager G4 Team Issue |
| Hub | DT Swiss 350 | not listed |
| Brake | SRAM Guide RS | Avid Code |
| Stem | Specialized P.Series | Bontrager Rhythm |
| Grips | Specialized Sip Grip | not listed |
| Saddle | Specialized Phenom Comp | Bontrager Evoke 2 |
| Frame | not listed | Trek Alpha Platinum |
| Wheelset | not listed | DT Swiss FR2150 |
| Handlebar | not listed | Bontrager Rhythm Elite |
| Headset | not listed | FSA NO.57E |
| Seatpost | not listed | Bontrager Rhythm Elite |
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