Year old Giant Defy 1, carbon post is stuck in the (alu) seat tube.
I’ve not tried really yanking on it/twisting it yet, as don’t want to damage the carbon.

What is the best way to get it out??

I’ve got a workshop full of tools, and know what I’m doing with them, but not had any experience of this.

When I get it out, what should I reassemble it with? is ‘carbon assembly paste’ just snake oil? can I use regular grease?

Coca-cola.

Grease could be the cause of the problem- it has been known to stick carbon to stuff. Assembly past is the good stuff.

I’d try Coke poured down from the BB shell with the frame upside down first. If that fails it’ll be time to put an old saddle on it, clamp that in a vice and get twisting.

Hot water around the top of the seat tube and some WD40. It isn’t corrosion, so will respond to expansion. Worked for my steel frame and an old carbon post.

Heat the frame with a hair dryer. Aluminium has almost 3* the thermal expansion coefficient of most CFRPs. If you can get it to 150-180deg it should start to move.

[Too slow]

I have a carbon post stuck, been in my Jake the Snake since 2010. Nothing will budge it. I suspect the Alu has corroded slightly internally with road salt, etc.

I’m resolved to using the above method eventually, when I finally have to moove it.. 😕

Aluminium oxide takes up considerably more space than the metal, hence the problem.

Put it in a vice and twist the bike around it, but first warn your neighbours that the noise they’ll hear is not you torturing a duck.

This guy gets good results and reviews :

http://www.theseatpostman.com/home

I highly reccomend The Seatpostman – http://www.theseatpostman.com/

well worth the slight expense as compared to a foobarred frame.