What is the best clamp size for a 27.2 seatpost?
Frame is Cotic 853 if that makes any difference.

Hope for example do – Bolt Seat Clamp Sizes:
28.6, 30.0, 31.8, 34.9, 36.4, 38.5

I guess 30 but is that right?

Well I got a 28.6mm clamp to fit my cotic although I think a 30mm might work

It's the outer diameter of the seat tube that dictates the size of your seatclamp – not the post itself. I'm almost 100% that Cotic Souls (if that's what it is) are a 30.0, but you'd best check on the Cotic site. Best of luck.

can you measure the top of the seat tube? orange bikes all use a 27.2 post with a 31.8 clamp.
joe

Just checked by measuring seat tube and 30.0 it is, thanks.

I have a 30.9 seatpost, bu my current clamp says 34 on it, I cant find anywhere that does 34 diameter clamps, any ideas? would a 34.9 work?