Originally Posted by
onespeedbiker
Believe me this was a serious concern, but my situation is quites different. The amoutn of seatpost I need is only 80mm above the crown. I cut the 300mm post down to 200mm; there is 120mm of post in the seat tube. Speaking of max lines, Nitto seems to have a lot of faith in seattubes as the max line on the 300mm post is only 65mm; looking at it it just didn't seem to be enough (if you look at the photo I attached closely you can see the max line; it's the second line from the bottom.
65cm is plenty of insertion depth for a post into a tube. It exceeds 2 diameters which is the rule of thumb for the first condition of safe fit. When you see deeper insertion depths such as on certain Thomson posts, it isn't because the post would tear out of the tube. It's because the OEM customer has a seat tube that extends above the seat tube, so the minumum insertion is increased to get the bottom of the post to below the bottom of the top tube (second condition of correct fit).