Originally Posted by
LarrySellerz
To use a contrived example, if you imagine a 3 foot long seatpost in a mithril frame, the line that is sufficient to protect the seatpost would crack a normal frame. you would have to shove a lot more into the bike if you have a massive post to avoid cracking the frame. Take that post on a mithril frame and go over the line by 6 inches and youre totally fine because the line is to protect the system as a whole and on the extreme long end of posts the frame is the weak point.
On a super short post, the post becomes the weak point and primary consideration. Dang now that I typed it out it seems obvious
For a simpler example, put a metal pipe into a vice/clamp. Leave 1" sticking out and try to bend it - virtually impossible. Try again with 6", 12", etc and you'll eventually find a point where it's easy to bend. Then you can mark a line just above where it transitions from hard to bend to easy to bend and that's your minimum insertion point.
The seat post should bend before the frame is damaged - it's thinner and weaker, so I'm not sure why a seat post manufacturer would be worried about damaging the frame.