400 mm seat post on 17.5" frame: too much insertion into frame?
i borrowed a relatives' trek 17.5" frame and used a 400 mm seat post to make it fit me. now i am returning it to him so he doesn't need the extra height of the seat post. however, we lost the original seat post.
question: a 400 mm seat post will have extra insertion into the frame - can this damage the frame?
we more commonly hear minimum insertion but is there such a thing as "maximum insertion?"
Can't think of a way it would hurt anything; it might not go in all the way if it hits a bottle boss or something. Deeply inserted posts can be a source of mysterious once-per-crank-revolution clicking noises and can retain water, so just grease up the end of the seat post before putting it in.
You can also just take a hacksaw and cut it down, as long as enough remains below the top of the seat tube -- if the min insert line is 4" from the end, say, you can cut it down as long as you're putting at least 4" of shortened post in the seat tube.