Library › Everyday mounts › Bicycle seatpost diameters: 25.4, 26.8, 27.2, 28.6, 30.9, 31.6 and…

Seatpost section Ø25.4 × 100 long, axis on X

Seatpost section Ø25.4 × 100 long, axis on X: the outside of the post (the wall is not drawn); DXF = the exact Ø25.4 circle

Exact dimensions. True size, no printing tolerance added. Threads are plain cylinders at the major diameter.

STEP STL DXF free, CC BY 4.0 (credit "Xem Studio")

Dimensions

post Ø (mm)Ø25.4
where it is used1 in posts on older and lower-cost frames
fromSheldon Brown
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From the full sheet

Bicycle seatpost diameters: 25.4, 26.8, 27.2, 28.6, 30.9, 31.6 and 34.9 mm: every size, notes, mating features and sources. What diameter is a bike seatpost?

Other sizes