Removing seized bottom bracket cups

I’ve just attempted to remove my GXP bottom bracket and it appears to be seized despite liberally applying copper grease when I installed it. Any advice for removing it? I thought of applying gentle heat to the BB shell but am worried about damaging the bearings or spacers.

PlusGas, and lots of it. Blast from the outside and also down the seattube/through the bottle cage mounts (if applicable). Slosh it round, let it soak for a while, repeat, and then removing it again.

Don’t use WD40: it’s not a “proper” penetrating oil hence it’s rubbsih for freeing seized threads.

Okay, thanks. I’ll get some tomorrow.

Rather than heating the BB shell you could try cooling the BB itself using a pipe freezing spray kit, available from B&Q etc. I successfully used this to remove a stuck pivot bolt on my FS bike. Good luck.

you are turning it the right way as one side goes the wrong way Clockwise to undo?

A nice sharp blow from a nice dead-blow type hammer I find does the trick.
(You know the type the plastic/rubber covered ones)

Halfords sell similar stuff to freeze spray but I think this has some penetrating oil in it also.
Halfords link.

Slight hijack – As I’m just about to install some outside bearing cranks (for the first time) any recommendations on what I should use to grease the threads?

Bimbler …copper grease