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

27.2 mm seatpost (27.2 mm) vs 31.6 mm seatpost (31.6 mm): specs compared

Updated 05 September 2026.

3
specs differ

27.2 mm seatpost (27.2 mm) and 31.6 mm seatpost (31.6 mm) differ on 3 specs: diameter, designation, typical frames.

Spec27.2 mm seatpost (27.2 mm)31.6 mm seatpost (31.6 mm)
Diameter27.2 mm31.6 mm
Designation27.2 mm31.6 mm
Typical framesthe de facto standard on modern road and gravel frames, and many hardtail and lightweight full-suspension framesmany mountain bikes and gravel frames, older oversized road frames, and the other common dropper-post diameter

Questions and answers

How do 27.2 mm seatpost (27.2 mm) and 31.6 mm seatpost (31.6 mm) compare?

27.2 mm seatpost (27.2 mm) and 31.6 mm seatpost (31.6 mm) differ on 3 specs: diameter, designation, typical frames.

Compared here

27.2 mm seatpost (27.2 mm)31.6 mm seatpost (31.6 mm)