In theory would it be possible to cut out and replace day the top 150mm of a seat tube and replace with a wider diameter tube?
Say 27.2mm ST to 30.9mm?
You can do what you want.
It would probably look awful.
You would need to flute from 27.2 to 30.9.
You would need to cut and re weld the seatstays.
If the frame is aluminum you need aluminum weler. You need to heat treat.
Why on earth would you want to do such a daft thing? Dropper post I assume.
I wouldn't trust riding it.
Just buy a new frame.
It's what Lynskey do, although they do it the opposite way round to keep the same OD with a smaller ID where the seat post goes in.
It's a sort of bodge way of butting a titanium tube.
A new Lynskey frame.
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Mine was the old one piece plain gauge tube design, until it cracked, but came back with the new stronger spigotted top section after repair.
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It's what Lynskey do, although they do it the opposite way round to keep the same OD with a smaller ID where the seat post goes in.
It's a sort of bodge way of butting a titanium tube.A new Lynskey frame.
Never knew that, that looks crap on a frame of that value!
The lynksey solution is easier as it fits into a bigger seat tube. That gives strength.
The OP's will be a hell of a lot weaker.
I did say they were random musings 😉
Why would it be weaker?
Assuming it was a steel frame (and as such did require post weld treating), and that the new section "sleeved" a section of the original ST what could go wrong?
My old Clark Kent has similar but I can't for the life of me work out why as the ID of the top section is the same as the ID for the lower section 😕
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