2026 Polygon Siskiu T T6 UDH vs 2026 Forbidden Reya Tier
The S4 is the Forbidden Reya Tier size closest to your XL Polygon Siskiu T T6 UDH. 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 T6 UDH in XL, the Forbidden Reya Tier in S4 places the top of the head tube 3 mm higher and 10 mm further back, relative to the bottom bracket. Its wheelbase is 18 mm longer, which can contribute to stability at speed.
- Frame stack
- +3 mm
- Higher front end
- Frame reach
- −10 mm
- Shorter frame reach
- Wheelbase
- +18 mm
- Longer: steadier at speed
- 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 T6 UDH is drawn. The Forbidden Reya Tier numbers we have for size S4 are missing the chainstay length.
Geometry side by side
| Measurement | Polygon Siskiu T T6 UDH XL | Forbidden Reya Tier S4 | Difference |
|---|---|---|---|
| Reach | 505 | 495 | −10 mm |
| Stack | 636 | 639 | +3 mm |
| Head tube angle | 64.5 | 65.0 | +0.5° |
| Seat tube angle | 71.2 | 75.2 | +4.0° |
| Effective top tube | 644 | 642 | −2 mm |
| Chainstay length | 430 | not listed | |
| Wheelbase | 1267 | 1285 | +18 mm |
| BB height | 337.5 | 331 | −7 mm |
| Standover | 723 | 721 | −2 mm |
| Seat tube length | 430 | 470 | +40 mm |
| Head tube length | 125 | 135 | +10 mm |
| Fork length | not listed | 541 |
Differences are the Forbidden Reya Tier minus the Polygon Siskiu T T6 UDH. Full charts: 2026 Polygon Siskiu T T6 UDH, 2026 Forbidden Reya Tier.
Where each sits in its class
Polygon Siskiu T T6 UDHForbidden 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 T6 UDHT6 with UDH | Forbidden Reya TierTier 1 |
|---|---|---|
| Frame | Polygon ALX Trail | Forbidden Reya |
| Fork | RockShox Recon Silver TK | Fox 34 Factory SL |
| Rear shock | X-Fusion O2 Pro | Fox Float Factory |
| Shifter | Shimano CUES | SRAM Pod Rocker Controller |
| Derailleur | Shimano CUES | SRAM XX XX SL |
| Cassette | Shimano CUES | SRAM XX SL Eagle Transmission |
| Chain | KMC XGlide | SRAM XX SL |
| Crankset | Samox RAC61C | SRAM XX SL |
| Pedals | Polygon Expert | not listed |
| Wheelset | Polygon MT6 | not listed |
| Tire | Maxxis Dissector | Maxxis Rekon Race |
| Brake | Shimano MT200 | SRAM Motive Ultimate |
| Rotor | Shimano SM-RT10 | 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 LC | OneUp Components V3 Dropper Post |
| Saddle | Linc XTENT | fizik Terra Ridon X1 |
| Chainring | not listed | SRAM 32T |
| 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 |
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