2018 Specialized Demo I Alloy vs 2020 Trek Session AL 27.5 Frameset
The S is the Trek Session AL 27.5 Frameset size closest to your SHORT Specialized Demo I 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 AL 27.5 Frameset
Compared with the Specialized Demo I Alloy in SHORT, the Trek Session AL 27.5 Frameset 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 I Alloy is drawn. The Trek Session AL 27.5 Frameset numbers we have for size S are missing the seat angle.
Geometry side by side
| Measurement | Specialized Demo I Alloy SHORT | Trek Session AL 27.5 Frameset 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 | 9 | −3 mm |
| BB height | 342mm | 364 | +22 mm |
| Standover | 698mm | 810 | +112 mm |
| Seat tube length | 367mm | 426 | +59 mm |
| Head tube length | 105mm | 115 | +10 mm |
Differences are the Trek Session AL 27.5 Frameset minus the Specialized Demo I Alloy. Full charts: 2018 Specialized Demo I Alloy, 2020 Trek Session AL 27.5 Frameset.
Where each sits in its class
Specialized Demo I AlloyTrek Session AL 27.5 Frameset
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 I Alloy8 I Alloy | Trek Session AL 27.5 FramesetAL 27.5 Frameset |
|---|---|---|
| Fork | RockShox BoXXer Team 27.5 | not listed |
| Rear shock | Fox Van RC | not listed |
| Shifter | SRAM X-7 | not listed |
| Derailleur | SRAM GX | not listed |
| Cassette | SRAM PG-1030 | not listed |
| Chain | SRAM PC-1031 | not listed |
| Crankset | SRAM Descendant | not listed |
| Pedals | Specialized Bennies | not listed |
| Tire | Specialized Butcher | not listed |
| Brake | SRAM Guide R | not listed |
| Stem | Specialized two-piece | not listed |
| Grips | Specialized Sip Grip | not listed |
| Saddle | Specialized Phenom Comp | not listed |
| Frame | not listed | Trek Alpha Platinum |
| Headset | not listed | FSA Orbit |
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