sport / default rider 183 cm
Aprilia RS4 125 vs BMW R 90 S ergonomics
Aprilia RS4 125 and BMW R 90 S have modeled posture scores within three points for the 183 cm default rider. Treat this as a planning estimate; posture preference, data confidence, and a real test sit still matter.
Modeled fit comparison
Aprilia RS4 125
All contacts reached
BMW R 90 S
All contacts reached
The modeled scores are within three points, so the result does not distinguish a higher-scoring bike. Treat the result as a planning estimate and compare each bike's geometry confidence before a real test sit.
Rider fit: reaching the ground
The Aprilia RS4 125 lists a 820 mm seat; the BMW R 90 S lists 820 mm, within a few millimetres of each other. Seat height is only a first-pass ground-reach input. It does not establish safety or actual foot contact. Seat width, suspension sag, boots, mobility, load, and individual proportions can materially change the result.
Geometry snapshot
| Spec | Aprilia RS4 125 | BMW R 90 S |
|---|---|---|
| Seat height | 820 mm | 820 mm |
| Wheelbase | 1,353 mm | 1,465 mm |
| Wet weight | 144 kg | 215 kg |
| Displacement | 124 cc | 898 cc |
Posture metrics
Knee angle
- Aprilia RS4 125
- Sport (60.7 deg)
- BMW R 90 S
- Sport (60.7 deg)
Hip angle
- Aprilia RS4 125
- Neutral (99.6 deg)
- BMW R 90 S
- Neutral (99.5 deg)
Elbow angle
- Aprilia RS4 125
- Relaxed (143.3 deg)
- BMW R 90 S
- Relaxed (143.3 deg)
Torso lean
- Aprilia RS4 125
- Forward (25.2 deg)
- BMW R 90 S
- Forward (25.8 deg)