Originally Posted by
unterhausen
I've always been confused about how much clearance you should have for a seatpost. I don't think there is an industry standard. Some seatposts are undersized, and sometimes people want to use them on frames that have an oversized seat tube ID.
This is my current dilemma. The seat tube is 0.5mm diameter larger than the nominal post. (31.6mm post in a 32.1mm hole) There are some (probably most) in the industry that try to make these as tight as possible. Is there a valid reason for that due to a history of frame failures or just paranoia? The only given is that if it is tight enough there will be NO flex and therefore NO possibility of fatigue failure.
I can also see a potential issue with retention and slippage as a large clearance will reduce the contact area between the post and the tube. Basically the only contact is at the top of the seat tube and not the whole width of the clamp.