Seat Clamps
Used road bike seat clamps in 28.6mm, 30.9mm, 31.6mm, 34.9mm and other sizes, from sellers across the UK. Quick-release and bolt-on styles from Thomson, Hope, Salsa and Wolf Tooth turn up regularly. Measure before you buy — the clamp size follows your frame, not your seatpost.
Why does the seat clamp matter?
It's a small part, but the wrong size means your seatpost slips or won't clamp at all. Seat clamp diameter matches your frame's seat tube outer diameter — not your seatpost diameter, which is the mistake most people make when ordering one blind.
What size seat clamp do I need?
The common sizes are 28.6mm (for 25.4mm posts), 30.0mm (for 27.2mm posts), 31.8mm (for 27.2mm posts on some carbon frames), 34.9mm (for 31.6mm posts) and 36.4mm (for 33.9mm posts). Measure your seat tube at the top, or check your frame specs before buying.
Quick-release or bolt-on?
Quick-release clamps are convenient if you adjust saddle height often or remove the post for transport. Bolt-on clamps are lighter, more secure as a theft deterrent, and cleaner-looking — the standard choice on road bikes.
Which material is worth paying for?
Alloy clamps weigh 15-30g and work perfectly, and the anodised finishes are an easy way to pick up the colour of your bar tape. Carbon clamps save a few grams but are fragile if overtightened. Titanium bolt upgrades save 2-3g if you're counting every gram, which is the same maths that applies across the rest of your road components.