EC49 headset standard (external cup, 49.6 mm)
What a EC49 headset measures under the SHIS standard, and how to tell it apart from lookalikes.
Published dimensions
| SHIS designation | EC49 (external cup (EC)) |
|---|---|
| Cup / bearing outside diameter | 49.6 to 49.7 mm cup outside diameter |
| Steerer diameter | 38.1 mm (1 1/2 in) |
| Crown race | 40.0 mm crown race seat |
Used on: 1 1/2 in external-cup lowers on frames with a straight 1.5 head tube.
EC49 is the 1 1/2 in external cup: a 49.6 mm bore for a 38.1 mm steerer and 40 mm crown race. It is the external-cup sibling of ZS49 and is not interchangeable with the 44 mm standards.
Frames and related headsets
EC34external cup, 34 mmEC44external cup, 44 mmZS44zero stack, 44 mmZS55zero stack, 55 mmIS41integrated, 41 mmBSA bottom bracket shellthe frame's other threaded interface
SOURCES: Park Tool, Standardized Headset Identification System (SHIS) · BikeGremlin, Bicycle headset bearing standards (SHIS)