Originally Posted by
urbanknight
If the inner diameter is consistent, then yes, but that's not the case most of the time. That means there is a small gap between the seatpost and the seat tube. If anything, a long seatpost rocks back and forth slightly, scratching the inside of the tube (not a big deal, but you get the idea).
OIC, the thinner wall = larger inside diameter. That makes sense, we're worried more about bending than banging so we keep a larger tube. Is that just carbon fiber with thinning the inside walls and not aluminum or steel?