2026 Polygon Siskiu T T8 vs 2026 Forbidden Reya Tier
The S1 is the Forbidden Reya Tier size closest to your S 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 Forbidden Reya Tier
Compared with the Polygon Siskiu T T8 in S, the Forbidden Reya Tier in S1 places the top of the head tube 6 mm lower and 5 mm further back, relative to the bottom bracket. Its wheelbase is 23 mm shorter, which can contribute to quicker direction changes.
- Frame stack
- −6 mm
- Lower front end
- Frame reach
- −5 mm
- Shorter frame reach
- Wheelbase
- −23 mm
- Shorter: quicker to change direction
- Head angle
- +0.5°
- Steeper: sharper steering
- Chainstays
- n/a
- One of the bikes has no number for this
The two frames
Only the Polygon Siskiu T T8 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 T8 S | Forbidden Reya Tier S1 | Difference |
|---|---|---|---|
| Reach | 440 | 435 | −5 mm |
| Stack | 604 | 598 | −6 mm |
| Head tube angle | 64.5 | 65.0 | +0.5° |
| Seat tube angle | 71.2 | 68.9 | −2.3° |
| Effective top tube | 568 | 573 | +5 mm |
| Chainstay length | 430 | not listed | |
| Wheelbase | 1186 | 1163 | −23 mm |
| BB height | 337.5 | 331 | −7 mm |
| Standover | 704 | 715 | +11 mm |
| Seat tube length | 390 | 400 | +10 mm |
| Head tube length | 89 | 90 | +1 mm |
| Fork length | not listed | 541 |
Differences are the Forbidden Reya Tier minus the Polygon Siskiu T T8. Full charts: 2026 Polygon Siskiu T T8, 2026 Forbidden Reya Tier.
Where each sits in its class
Polygon Siskiu T T8Forbidden 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 T8T8 | Forbidden Reya TierTier 1 |
|---|---|---|
| Frame | Polygon Siskiu T | Forbidden Reya |
| Fork | Fox 34 Float Rhythm | Fox 34 Factory SL |
| Rear shock | Fox Float P-S | Fox Float Factory |
| Shifter | Shimano SL-M7100-R SLX | SRAM Pod Rocker Controller |
| Derailleur | Shimano SLX | SRAM XX XX SL |
| Cassette | Shimano SLX | SRAM XX SL Eagle Transmission |
| Chain | KMC X-12 | SRAM XX SL |
| Crankset | Shimano SLX | SRAM XX SL |
| Chainring | Shimano SLX | SRAM 32T |
| Wheelset | Polygon MT6 | not listed |
| Tire | Maxxis Dissector | Maxxis Rekon Race |
| Brake | Shimano Deore M4100 | SRAM Motive Ultimate |
| Rotor | Shimano Rotor | SRAM HS2 |
| Handlebar | Polygon EXPERT | OneUp Components Carbon |
| Headset | FSA headset | Cane Creek 40 |
| Dropper post | Polygon Expert | OneUp Components V3 Dropper Post |
| Bottom bracket | not listed | SRAM DUB |
| 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 |
| Stem | not listed | BikeYoke Barkeeper Stem |
| Saddle | not listed | fizik Terra Ridon X1 |
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