2026 Ibis Oso HD vs 2026 Forbidden Heathen Framekit
The Forbidden Heathen Framekit size closest to your XM is the S3. Compare the S3 instead
What changes on the Forbidden Heathen Framekit
Compared with the Ibis Oso HD in XM, the Forbidden Heathen Framekit in S4 places the top of the head tube at about the same height and 21 mm further forward, relative to the bottom bracket. Its wheelbase is 24 mm shorter, which can contribute to quicker direction changes.
- Frame stack
- +2 mm
- About the same height
- Frame reach
- +21 mm
- Longer frame reach
- Wheelbase
- −24 mm
- Shorter: quicker to change direction
- Head angle
- +0.9°
- Steeper: sharper steering
- Chainstays
- n/a
- One of the bikes has no number for this
The two frames
Only the Ibis Oso HD is drawn. The Forbidden Heathen Framekit numbers we have for size S4 are missing the chainstay length.
Geometry side by side
| Measurement | Ibis Oso HD XM | Forbidden Heathen Framekit S4 | Difference |
|---|---|---|---|
| Reach | 474 | 495 | +21 mm |
| Stack | 646 | 648 | +2 mm |
| Head tube angle | 63.1 | 64 | +0.9° |
| Seat tube angle | 76.6 | 76 | −0.6° |
| Chainstay length | 455 | not listed | |
| Wheelbase | 1295 | 1270.6 | −24 mm |
| BB drop | 21 | not listed | |
| BB height | 352 | 311 | −41 mm |
| Standover | 745 | 764 | +19 mm |
| Seat tube length | 405 | 470 | +65 mm |
| Head tube length | 121 | 120 | −1 mm |
| Effective top tube | not listed | 657 | |
| Fork length | not listed | 541 |
Differences are the Forbidden Heathen Framekit minus the Ibis Oso HD. Full charts: 2026 Ibis Oso HD, 2026 Forbidden Heathen Framekit.
Where each sits in its class
Ibis Oso HDForbidden Heathen Framekit
Each bike is ranked against the other trail bikes on Quiver, on frame geometry alone. Not your hand position or ride feel.
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