IS41 headset standard (integrated vs ZS55 headset standard (zero stack: specs compared
Updated 05 September 2026.
4
specs differ
IS41 headset standard (integrated and ZS55 headset standard (zero stack differ on 4 specs: shis designation, cup / bearing outside diameter, steerer diameter, crown race.
| Spec | IS41 headset standard (integrated | ZS55 headset standard (zero stack |
|---|---|---|
| SHIS designation | IS41 (integrated (IS)) | ZS55 (zero stack (ZS)) |
| Cup / bearing outside diameter | 41.0 to 41.1 mm bearing outside diameter | 55.0 mm cup outside diameter, 54.9 to 54.95 mm head-tube bore |
| Steerer diameter | 28.6 mm (1 1/8 in) | 38.1 mm (1 1/2 in) |
| Crown race | 30.0 mm crown race, or machined into the fork | 40.0 mm crown race seat |
Questions and answers
How do IS41 headset standard (integrated and ZS55 headset standard (zero stack compare?
IS41 headset standard (integrated and ZS55 headset standard (zero stack differ on 4 specs: shis designation, cup / bearing outside diameter, steerer diameter, crown race.