2027 Polygon Siskiu T T27 EVO vs 2026 Forbidden Reya Tier
The S1 is the Forbidden Reya Tier size closest to your XS Polygon Siskiu T T27 EVO. 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 Forbidden Reya Tier
Compared with the Polygon Siskiu T T27 EVO in XS, the Forbidden Reya Tier in S1 places the top of the head tube 18 mm higher and 15 mm further forward, relative to the bottom bracket. Its wheelbase is 17 mm longer, which can contribute to stability at speed.
- Frame stack
- +18 mm
- Higher front end
- Frame reach
- +15 mm
- Longer frame reach
- Wheelbase
- +17 mm
- Longer: steadier at speed
- Head angle
- ±0.0°
- About the same head angle
- Chainstays
- n/a
- One of the bikes has no number for this
The two frames
Only the Polygon Siskiu T T27 EVO is drawn. The Forbidden Reya Tier numbers we have for size S1 are missing the chainstay length.
Geometry side by side
| Measurement | Polygon Siskiu T T27 EVO XS | Forbidden Reya Tier S1 | Difference |
|---|---|---|---|
| Reach | 420 | 435 | +15 mm |
| Stack | 579.87 | 598 | +18 mm |
| Head tube angle | 65 | 65.0 | ±0.0° |
| Seat tube angle | 71 | 68.9 | −2.1° |
| Effective top tube | 559.2 | 573 | +14 mm |
| Chainstay length | 425 | not listed | |
| Wheelbase | 1146.4 | 1163 | +17 mm |
| BB height | 335 | 331 | −4 mm |
| Standover | 666 | 715 | +49 mm |
| Seat tube length | 375 | 400 | +25 mm |
| Head tube length | 90 | 90 | ±0 mm |
| Fork length | not listed | 541 |
Differences are the Forbidden Reya Tier minus the Polygon Siskiu T T27 EVO. Full charts: 2027 Polygon Siskiu T T27 EVO, 2026 Forbidden Reya Tier.
Where each sits in its class
Polygon Siskiu T T27 EVOForbidden Reya Tier
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 T27 EVOT27 EVO | Forbidden Reya TierTier 1 |
|---|---|---|
| Frame | Polygon ALX Trail | Forbidden Reya |
| Fork | RockShox Recon Silver TK | Fox 34 Factory SL |
| Rear shock | RockShox Deluxe Select+ | Fox Float Factory |
| Shifter | Shimano Deore M6100 | SRAM Pod Rocker Controller |
| Derailleur | Shimano Deore M6100 | SRAM XX XX SL |
| Cassette | Shimano Deore M6100 | SRAM XX SL Eagle Transmission |
| Chain | KMC X-12 | SRAM XX SL |
| Crankset | Shimano Deore M6120 | SRAM XX SL |
| Chainring | Shimano 32 | SRAM 32T |
| Bottom bracket | Shimano | SRAM DUB |
| Pedals | Alloy | not listed |
| Wheelset | Polygon MT6 | not listed |
| Tire | Maxxis Dissector | Maxxis Rekon Race |
| Brake | Shimano Deore M4100 | SRAM Motive Ultimate |
| Rotor | Shimano SM-RT54 | SRAM HS2 |
| Handlebar | Polygon EXPERT | OneUp Components Carbon |
| Stem | Polygon EXPERT | BikeYoke Barkeeper Stem |
| Headset | FSA No 57E | Cane Creek 40 |
| Dropper post | X-Fusion Manic | OneUp Components V3 Dropper Post |
| Seatpost | Dropper Post | not listed |
| Saddle | fizik Terra Alpaca X5 | fizik Terra Ridon X1 |
| Battery | not listed | SRAM AXS EP Powerpack |
| Hub | not listed | DT Swiss 240 SPLINE, DT Swiss 240 SPLINE Ratchet EXP |
| Rim | not listed | DT Swiss 1500 |
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