34.9 mm seatpost (34.9 mm)
Which frames use a 34.9 mm seatpost, and how it differs from the sizes either side of it.
Published dimensions
| Diameter | 34.9 mm |
|---|---|
| Designation | 34.9 mm |
| Typical frames | modern trail and enduro mountain frames wanting the largest, stiffest dropper interface |
Used on: modern trail and enduro mountain frames wanting the largest, stiffest dropper interface.
34.9 mm is the newest mainstream MTB size, giving the largest and stiffest dropper interface and room for longer-travel droppers. It is a mountain-bike size; road and gravel frames do not use it. A 31.6 mm post needs a shim to run in a 34.9 mm frame.
Frames and related seatpost sizes
Seatpost on a Specialized Stumpjumper (2019 on carbon)34.9 mmSeatpost on a Santa Cruz Hightower34.9 mmSeatpost on a Santa Cruz Megatower34.9 mm27.2 mm seatpost27.2 mm30.6 mm seatpost30.6 mmBSA bottom bracket shellthe frame's other threaded interface
SOURCES: BikeGremlin, Seatpost diameter sizes (standards) · BikeRadar, Bike seatposts explained: diameters, materials, lengths