Seatposts
Used road seatposts in 27.2mm, 30.9mm, and 31.6mm diameters, listed by sellers across the UK. Alloy and carbon options from Thomson, Ritchey, Zipp, Canyon, Deda, and PRO, including setback and inline designs.
What diameter seatpost do I need?
Diameter, setback, and material between them set your comfort, weight, and saddle position. 27.2mm is the traditional road standard and still the most common. Many modern carbon frames use proprietary sizes — 30.9mm, 31.6mm, or even D-shaped aero profiles. Measure your seat tube or check your frame specs. Shims exist but add weight and can creak.
Setback or inline?
Setback posts (15-25mm offset) push the saddle rearward — useful for riders who need more behind-the-BB saddle position. Inline (zero setback) posts are for riders who sit forward, common on TT bikes and compact geometry frames. Your bike fitter can tell you which you need, usually at the same time as saddle height and pedal position.
Alloy or carbon?
Alloy posts (Thomson Elite, Ritchey Classic) weigh 200-250g and are bombproof. Carbon posts (Zipp SL Speed, PRO Vibe) drop to 150-180g and offer slight vibration damping. Some carbon posts like the Canyon VCLS use a leaf-spring design for genuine compliance over rough roads.
What should I check buying used?
Check for scoring or scratches from seat clamps — deep marks on carbon posts are a safety concern. Look at the saddle clamp mechanism for stripped threads or damaged cradle rails, and make sure the minimum insertion line isn't exposed above the frame. The same inspection is worth doing on any second-hand road components you buy.