Stuck seat posts
There's plenty been written about methods to deal with these and I don't agree with a lot of it, I'll explain why:
Firstly: why do they stick? Generally the cause is corrosion of an aluminium component (frame, seat post or both) the oxide swells and jams the post in place. The corrosion is exacerbated by galvanic (electrical issues) between the two components, carbon isn't immune, it is a good conductor. I've occasionally seen carbon stick to carbon, perhaps because something swells a little, I'm uncertain.
Various methods of removal have been suggested:
-Heat: heating things up rarely helps much, the differential expansion of the components is negligible, it doesn't do a lot for the oxide layer causing the trouble, it can wreck your paint, it's no use on a carbon frame.
-Sawing slots: this is tedious even with an air saw, you need a custom made blade guard to control depth or the frame can be damaged, the top of the post will need lopping for access (limiting other removal options), if there's a lot of post in the frame it will be a nightmare.
-Caustic soda: it's posible to dissolve an aluminium post out of a steel frame with a solution of caustic soda. I've done this it's nice and exciting in a slightly dangerous way. It's messy and takes ages. Don't get it on the paintwork.
-Sticking the post in a vice and using the frame as a lever: a horrible thing to do to a frame, even if you overcome the seized friction element and rotating the seat post doesn't necessarily remove it. In addition the bike has to be upside down and as everyone knows if this happens all the luck will fall out of it.
- Soaking with release fluid: rubbish, it rarely gets down to the problem area, you can tell when you've removed one where this has been attempted.
- Drilling a hole in the bottom bracket and smashing the post with a long drift: apparently the drift fires out of the side of a £4000 carbon frame which has to be scrapped.
So how to remove them safely?
The answer seems to be the rather obvious "pull them out" strategy. This requires some custom built machinery.
Either jack them out with a collar round the seat tube, or pull them out using the BB area as support. I prefer the former method as in extremis I wonder if it's possible to pull a frame apart, but it's difficult to fit a collar on with a dropper post.
A few photos to illustrate the process. The MkI compression/jack extractor and the MkII tension extractor. The MkII is currently having improved BB sleeves, clamp for the bike work stand, assorted post split collars and a thrust bearing added to make the job even less painless.
If you need help with a stuck seat post drop me an Email: firstname.lastname@example.org