2026 Polygon Siskiu T T8 vs 2025 Trek Fuel EX
The XL is the Trek Fuel EX size closest to your XL Polygon Siskiu T T8. 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 Fuel EX
Compared with the Polygon Siskiu T T8 in XL, the Trek Fuel EX in XL places the top of the head tube at about the same height and 10 mm further forward, relative to the bottom bracket. Its wheelbase is 20 mm longer, which can contribute to stability at speed.
- Frame stack
- −1 mm
- About the same height
- Frame reach
- +10 mm
- Longer frame reach
- Wheelbase
- +20 mm
- Longer: steadier at speed
- Head angle
- ±0.0°
- About the same head angle
- Chainstays
- +15 mm
- Longer: more planted
The two frames
Only the Polygon Siskiu T T8 is drawn. The Trek Fuel EX numbers we have for size XL are missing the seat angle.
Geometry side by side
| Measurement | Polygon Siskiu T T8 XL | Trek Fuel EX XL | Difference |
|---|---|---|---|
| Reach | 505 | 515 | +10 mm |
| Stack | 636 | 634.9 | −1 mm |
| Head tube angle | 64.5 | 64.5 | ±0.0° |
| Seat tube angle | 71.2 | not listed | |
| Effective top tube | 644 | 661.8 | +18 mm |
| Chainstay length | 430 | 445 | +15 mm |
| Wheelbase | 1267 | 1286.7 | +20 mm |
| BB height | 337.5 | 335 | −3 mm |
| Standover | 723 | 766.8 | +44 mm |
| Seat tube length | 430 | 470 | +40 mm |
| Head tube length | 125 | 120 | −5 mm |
| BB drop | not listed | 38 |
Differences are the Trek Fuel EX minus the Polygon Siskiu T T8. Full charts: 2026 Polygon Siskiu T T8, 2025 Trek Fuel EX.
Where each sits in its class
Polygon Siskiu T T8Trek Fuel EX
Each bike is ranked against the other trail 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 | Polygon Siskiu T T8T8 | Trek Fuel EX5 |
|---|---|---|
| Frame | Polygon Siskiu T | Trek Fuel EX |
| Fork | Fox 34 Float Rhythm | RockShox Recon Silver |
| Rear shock | Fox Float P-S | X-Fusion Pro 2 |
| Shifter | Shimano SL-M7100-R SLX | Shimano Deore M6100 |
| Derailleur | Shimano SLX | Shimano Deore M6100 |
| Cassette | Shimano SLX | Shimano Deore M6100 |
| Chain | KMC X-12 | Shimano Deore M6100 |
| Crankset | Shimano SLX | Shimano MT512 |
| Chainring | Shimano SLX | not listed |
| Wheelset | Polygon MT6 | Bontrager Line TLR 30 |
| Tire | Maxxis Dissector | Bontrager Gunnison Elite XR |
| Brake | Shimano Deore M4100 | Shimano MT200 |
| Rotor | Shimano Rotor | Shimano SM-RT56 |
| Handlebar | Polygon EXPERT | TranzX JD-YSI-22PLQ |
| Headset | FSA headset | not listed |
| Dropper post | Polygon Expert | TranzX JD-YSI-22PLQ |
| Bottom bracket | not listed | Shimano MT501 |
| Stem | not listed | Bontrager Comp |
| Grips | not listed | Bontrager XR Trail |
| Saddle | not listed | Bontrager Arvada |
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