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Idiot father, rebuilding my sons bike last night. One of those didn't think it through moments. New frame, new respray, Orange crush 2016. New dropper seat post, Race Fave Aeffect. Fitted it, very tight, should of stopped. Then realised cable too short (internal) Now can't get the bugger out. It moves approx 1/4 -1/2 turn back and forth but not up and down. The amount of force I am putting on the post can't be doing it any good, At the moment I just want to get it out. Tried hot water. Tried wd40 fast release penetrant from both sides as no bottom bracket fitted so had it upside down soaking for over an hour. Any suggestions without knackering the frame, seatpost wasn't cheap, but thats the least of my worries at the moment. cheers
WD40 'penetrating' oil, my second piece of advise would be a vice, but my old seatpost wasnt a consideration
coca cola was also recommeneded to me, that just made a sticky mess of my garage floor
As it's not a corrosion issue I doubt fluids such as wd40 are going to help here. Turning the sprung element of the dropper is probably not doing an awful lot of good to the dropper internals. I'd try and grip the inserted part of the post using something like an oil filter wrench with the post wrapped in old inner tube
or clamp the collar of the seat post in a vice and turn the frame.
slowly....
Its OUTTTTTTTTTTTT yeah
Woo hoo.
Does it still work??
Deleted - should have refreshed before replying. Nice one, is it horrifically scored?
Does it look like this?
horrifically scored, sanded cleaned and seat tube cleaned with wire wool on the end of a coat hanger connected to my drill, sweat now, works all fine.
How did you manage it please?
I'm in a similar issue but mines corrosion related.
It's a dropper post I need to get out so would help to understand the technique you used.
Try a hot air gun to heat the seat tube up. It might give you enough expansion to loosen its grip on the post. Hot air guns are only about 20 quid from Screwfix 😀
I've managed to release a stuck post by clamping an old stem to it, using an old fork for leverage, to get it moving. (I used penetrating oil, in advance of this) It must not have been full-on galvanic corrosion as they are almost impossible to remove when that occurs.
If you don't need to salvage the post, it is possible to cut them out with a hacksaw blade and a lot of patience.  It all depends on the type of frame and how deep the remnant of the cut- off post goes.
I've also heard of people using caustic soda to dissolve alloy posts in steel frames. Bit naughty, if you have kids or pets knocking around, though.
As above, heat also works, depending on the frame material.