seatpost

A seatpost is a bicycle component that connects the saddle to the frame’s seat tube and allows the rider to adjust saddle height. It is typically a hollow or solid tube inserted into the seat tube and topped by a saddle clamp to secure the rails.

Seatposts are made from various materials, including steel, aluminum alloy, titanium, and carbon fiber. They come in different diameters to fit the seat tube interior, with common modern sizes such as 27.2 mm, 30.9 mm, 31.6 mm, and 34.9 mm. Some posts are round, while others are aero or oval in cross-section, and many feature a setback (horizontal offset) that positions the saddle behind or in line with the seat tube for riding geometry.

Saddle clamps atop seatposts vary: single-bolt or two-bolt clamps are common, and some posts use more advanced micro-adjust clamps. The clamp choice affects rail grip and adjustment precision. Some seatposts are designed for dropper posts, which can lower the saddle via a cable- or hydraulic-actuated mechanism, typically used on mountain bikes.

Sizing and fit considerations include matching the post diameter to the seat tube, selecting a length that provides adequate saddle height while staying within minimum insertion and clamp limits, and ensuring proper alignment of the saddle rails. Many frames specify a minimum insertion line to prevent structural compromise.

Maintenance and safety guidelines advise cleaning the seatpost and seat tube, using manufacturer-recommended torque on all bolts, avoiding overtightening or overextension, and inspecting for damage or creaking. Carbon seatposts require compatible clamps and lubricants or pastes as recommended to prevent slippage and frame damage.