A Trek Domane AL (alloy) uses a IS42 integrated upper headset (integrated, 42 mm). The dimensions, how to confirm it on your frame, and how it compares to the neighbouring standards.
Updated 05 September 2026.
What headset does a Trek Domane AL (alloy) use?
The headset fitment standard on a Trek Domane AL (alloy), and how to pick the right part.
| Frame | Trek Domane AL (alloy) |
|---|---|
| Headset standard | IS42 (integrated, 42 mm) |
| Cup / bearing outside diameter | 41.8 to 42.0 mm bearing outside diameter |
| Steerer diameter | 28.6 mm (1 1/8 in) |
The Trek Domane AL (alloy) uses a IS42 integrated upper headset (integrated, 42 mm), a 27.2 mm class seatpost, a 12x100 mm front thru-axle at the front (12 mm x 100 mm, front) and a 31.8 mm band front derailleur.
An aluminium frame may have a round seat tube rather than a braze-on tab, so a clamp front derailleur can be needed; check the tube. The bottom bracket is covered on its own page.
SOURCES: Park Tool, Standardized Headset Identification System (SHIS) · BikeGremlin, Bicycle headset bearing standards (SHIS) · BikeRadar, Road bike axle standards: the complete guide
Questions and answers
What headset does a Trek Domane AL (alloy) use?
A Trek Domane AL (alloy) uses a IS42 integrated upper headset (integrated, 42 mm).