2026 Forbidden Reya Tier vs 2026 Polygon Siskiu T T8 UDH
The S is the Polygon Siskiu T T8 UDH size closest to your S1 Forbidden Reya Tier. 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 Polygon Siskiu T T8 UDH
Compared with the Forbidden Reya Tier in S1, the Polygon Siskiu T T8 UDH in S places the top of the head tube 6 mm higher and 5 mm further forward, relative to the bottom bracket. Its wheelbase is 23 mm longer, which can contribute to stability at speed.
- Frame stack
- +6 mm
- Higher front end
- Frame reach
- +5 mm
- Longer frame reach
- Wheelbase
- +23 mm
- Longer: steadier at speed
- Head angle
- −0.5°
- Slacker: calmer steering
- Chainstays
- n/a
- One of the bikes has no number for this
The two frames
We can't draw these frames yet. The Forbidden Reya Tier numbers we have for size S1 are missing the chainstay length. The numbers below still compare.
Geometry side by side
| Measurement | Forbidden Reya Tier S1 | Polygon Siskiu T T8 UDH S | Difference |
|---|---|---|---|
| Reach | 435 | 440 | +5 mm |
| Stack | 598 | 604 | +6 mm |
| Head tube angle | 65.0 | 64.5 | −0.5° |
| Seat tube angle | 68.9 | 71.2 | +2.3° |
| Effective top tube | 573 | 568 | −5 mm |
| Wheelbase | 1163 | 1186 | +23 mm |
| BB height | 331 | 337.5 | +7 mm |
| Standover | 715 | 704 | −11 mm |
| Seat tube length | 400 | 390 | −10 mm |
| Fork length | 541 | not listed | |
| Head tube length | 90 | 89 | −1 mm |
| Chainstay length | not listed | 430 |
Differences are the Polygon Siskiu T T8 UDH minus the Forbidden Reya Tier. Full charts: 2026 Forbidden Reya Tier, 2026 Polygon Siskiu T T8 UDH.
Where each sits in its class
Forbidden Reya TierPolygon Siskiu T T8 UDH
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 | Forbidden Reya TierTier 1 | Polygon Siskiu T T8 UDHT8 with UDH |
|---|---|---|
| Frame | Forbidden Reya | Polygon ALX Trail |
| Fork | Fox 34 Factory | Fox 34 Performance |
| Rear shock | Fox Float Factory | Fox Float |
| Shifter | SRAM Pod Rocker Controller | Shimano SLX M7100 |
| Derailleur | SRAM XX XX SL | Shimano SLX M7100 |
| Cassette | SRAM XX SL Eagle Transmission | Shimano SLX M7100 |
| Chain | SRAM XX SL | KMC X-12 |
| Crankset | SRAM XX SL | Shimano Deore M6120 |
| Chainring | SRAM 32T | not listed |
| Bottom bracket | SRAM DUB | not listed |
| Battery | SRAM AXS EP Powerpack | not listed |
| Tire | Maxxis Rekon Race | Maxxis Dissector |
| Hub | DT Swiss 240 SPLINE, DT Swiss 240 SPLINE Ratchet EXP | not listed |
| Rim | DT Swiss 1500 | not listed |
| Brake | SRAM Motive Ultimate | Shimano Deore M4100 |
| Rotor | SRAM HS2 | Shimano SM-RT54 |
| Handlebar | OneUp Components Carbon | Polygon EXPERT |
| Stem | BikeYoke Barkeeper Stem | Polygon EXPERT |
| Headset | Cane Creek 40 | FSA No 57E |
| Dropper post | OneUp Components V3 Dropper Post | X-Fusion MANIC LC |
| Saddle | fizik Terra Ridon X1 | Linc XTENT |
| Wheelset | not listed | Polygon MT6 |
Know what is on every bike.
Add your bike to Quiver. Keep its parts, setup, and service history together, then share your build.
Explore the app
