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Bike component fitment: bottom bracket, headset, seatpost, axle

31.6 mm seatpost (31.6 mm) vs 34.9 mm seatpost (34.9 mm): specs compared

Updated 05 September 2026.

3
specs differ

31.6 mm seatpost (31.6 mm) and 34.9 mm seatpost (34.9 mm) differ on 3 specs: diameter, designation, typical frames.

Spec31.6 mm seatpost (31.6 mm)34.9 mm seatpost (34.9 mm)
Diameter31.6 mm34.9 mm
Designation31.6 mm34.9 mm
Typical framesmany mountain bikes and gravel frames, older oversized road frames, and the other common dropper-post diametermodern trail and enduro mountain frames wanting the largest, stiffest dropper interface

Questions and answers

How do 31.6 mm seatpost (31.6 mm) and 34.9 mm seatpost (34.9 mm) compare?

31.6 mm seatpost (31.6 mm) and 34.9 mm seatpost (34.9 mm) differ on 3 specs: diameter, designation, typical frames.

Compared here

31.6 mm seatpost (31.6 mm)34.9 mm seatpost (34.9 mm)