34.9 mm front-derailleur clamp (34.9 mm band)
Which frames use a 34.9 mm band front-derailleur mount, and how to tell band from braze-on.
Published dimensions
| Mount / band size | 34.9 mm (1 3/8 in) seat-tube clamp |
|---|---|
| Designation | 34.9 mm band |
| Typical frames | oversized aluminium and some mountain frames with a large-diameter seat tube at the clamp |
Used on: oversized aluminium and some mountain frames with a large-diameter seat tube at the clamp.
34.9 mm is the largest common band size, for oversized 1 3/8 in seat tubes. A 31.8 mm clamp will not close around a 34.9 mm tube, so match the band to the measured tube. Shim kits step a 34.9 mm band down to 31.8 or 28.6 mm.
Frames and related mount sizes
28.6 mm front-derailleur clamp28.6 mm band31.8 mm front-derailleur clamp31.8 mm bandBraze-on (direct-mount) front derailleurbraze-on tabBSA bottom bracket shellthe frame's other threaded interfaceT47 bottom bracket shellthreaded BB, same frame
SOURCES: BikeRadar, Front derailleurs explained: types, mounts and compatibility · Shimano, SM-AD91 front derailleur clamp band adapter