Seatpost question

Triathlon Forum
1

I bought a bare frame off eBay recently (MTB frame). I measured the opening of the seat tube at 31.2mm (inside diameter) and 34.8mm (outside diameter). I’ve seen 31.6mm and 30.9mm diameter seatposts (and everything else all over the map). I’m thinking I should be using the 30.9mm seatpost. Is this correct? and will standard seatpost binders work on this frame?

Thanks!

2

Make sure the slit at the back of the seat tube is perfectly cut (i.e. not compressed). Then run a flex hone down the tube and see if it spins easier the further down the hone goes.

If it does, you may just be in need of a quick seat tube reaming out to 31.6mm.