What this headset is
A Syncros integrated drop-in headset designed exclusively for:
Brand: Syncros
Key Standards
-
Top: IS31/25.4
-
Bottom: IS41/30
-
Fork steerer: 1" → 1 1/8" tapered
Meaning:
- Top bearing seat: 31 mm internal / 25.4 mm steerer (1")
- Bottom bearing seat: 41 mm internal / 30 mm crown race
- Very narrow top = classic TT/triathlon design
System type
- Fully integrated (IS) “drop-in” bearings
- Not pressed cups (not ZS/EC)
- Sealed cartridge bearings
- Aluminium construction
Why this headset is unusual
This is a triathlon-specific tapered system, and it differs from all your previous ones:
- Uses 1" upper steerer (rare in modern bikes)
- Bottom is IS41, but with a 30 mm crown race standard
- Designed for aerodynamic stiffness + clean front end integration
Comparison with your other headset systems
| System |
Bike |
Top |
Bottom |
Fork |
Type |
| Plasma 5 |
TT/Tri |
IS31/25.4 |
IS41/30 |
1" → 1 1/8" |
IS |
| Foil 2023 |
Road aero |
IS44/35 |
IS52/40 |
1" → 1.5" |
IS |
| Scale/Spark |
MTB |
IS42/28.6 |
IS52/40 |
1 1/8" → 1.5" |
IS |
| Addict/Solace |
Road |
IS41/28.6 |
IS46/34 |
1 1/8" → 1 1/4" |
IS |
| ZS44/EC44 |
Road/MTB |
ZS44 |
EC44 |
1 1/8" |
Press-fit |
Key takeaway
This headset is:
- NOT compatible with Foil / Addict / Scale / Spark systems
- ❌ NOT interchangeable with any IS41/IS44/IS42 systems
- ✔️ ONLY for Plasma 5 frames
Even though it shares the “IS” name, the dimensions are completely unique.
Simple explanation
Think of it like this:
- IS44/52 systems → modern road & MTB
- IS41 systems → older road
- IS42 systems → older MTB
- IS31/41 system → TT-specific (Plasma 5 only)
When you should use it
Only if your bike is:
- Scott Plasma 5
- And your current headset markings match:
- IS31/25.4 (top)
- IS41/30 (bottom)
