Mark Bulgier wrote: "I've never owned a Cinelli so this is conjecture, but no tube on a lightweight bike could ever be that thick. I'm certain Cinellis must take such a small seatpost because there is an added sleeve inside the tube to strengthen the seatlug area. A smaller post could just indicate a thicker sleeve was used on yours."
Mark, you are correct. This is my first Cinelli and the seat post diameter intrigued me. So when the seat posts I had on hand, 26.8 and 27.2 didn't fit, I did poke my finger in to find that there is in fact a sleeve. It's obviously not very long if I can reach the bottom of it with my index finger. I am going to precisely measure the inside diameter at a bike shop tomorrow morning, then proceed accordingly in my search for the appropriate seat post.
Carlos Ovalle
Long Beach, California, USA