A Trek Emonda ALR (alloy) uses a 31.8 mm front-derailleur clamp for the front derailleur. The dimensions, how to confirm it on your frame, and how it compares to the neighbouring standards.
Updated 05 September 2026.
What front derailleur mount does a Trek Emonda ALR (alloy) use?
The front derailleur fitment standard on a Trek Emonda ALR (alloy), and how to pick the right part.
| Frame | Trek Emonda ALR (alloy) |
|---|---|
| Front derailleur mount | 31.8 mm front-derailleur clamp (31.8 mm band) |
| Mount / band size | 31.8 mm (1 1/4 in) seat-tube clamp |
| Typical class | the most common round-tube clamp size on aluminium road and touring frames |
The Trek Emonda ALR (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: BikeRadar, Front derailleurs explained: types, mounts and compatibility · Shimano, SM-AD91 front derailleur clamp band adapter · Park Tool, Standardized Headset Identification System (SHIS) · BikeRadar, Road bike axle standards: the complete guide
Questions and answers
What front derailleur mount does a Trek Emonda ALR (alloy) use?
A Trek Emonda ALR (alloy) uses a 31.8 mm front-derailleur clamp for the front derailleur.