Removing stuck or seized seatpost?

any ideas how to get my cheapo alloy seatpost out of my steel frame so i can put my nice new miche supertype in.
i've tried whacking it with a hammer and twisting it with a big spanner to no avail.

One slightly heavy-handed method that worked for me:

i) loosen the seatclamp
ii) spray some GT-85 or something in the general area (optional)
iii) make sure you've still got the saddle attached (important!)
iv) stand on the pedals/position yourself up in the air above the saddle.
v) sit down hard.
iv) repeat as necessary.

Seems to break the 'weld' enough to start twisting and and loosening (using the saddle as a lever).

Good luck.

Drown it with WD40 and let it soak in.. try again.

Too slow.. watching Alan Partridge is my excuse. ;)

If the WD40 doesn't work, perhaps try warming up the seat tube of the frame a bit? Get the tube to expand so that the seat post can loosen up.

Hmm maybe. Might need a hell of a lot of heat to cause it to expand significantly enough to the extent that it damages the frame.

:)

but that may cause the seat post to expand aswell...leaving you where you were originaly only with a bigger seat tube:P

If the amount of heat was just right the heat wouldn't quite get to the seat post as well. The two different materials would absorb and dissipate the heat at different rates as well!

Well, maybe. Just tons of WD40!

okay i've drenched it in wd40 gonna leave it overnight then try again

I had this problem with my last bike and basically there was no solution - or at least the mechanics at condor couldn't do anything with it. So the fecker who stole it better be the same height as me...

yup, drench it in wd40 and then you'll have to find a way to get lots of leverage. The broom handle idea sounds cool.. Another would be to clamp the seatpost in a vice (that's if you don't care too much for the post..) and twist the frame itself as a big lever.

If the WD40 doesn't work consider using a penetrating oil, like plusgas, I've found that to work well in the past. I've also used one of those chefs mini-blow torches you can get for caramelising creme brulee to gently heat up both stuck seatposts and pedals to get them out. If both metals have the same degree of thermal expansivity, the wider diameter seat tube will always expand by more than the narrower seatpost, unfortunately aluminium has a higher thermal expansivity than steel, but up to 400°C I don't think it's enough of a difference to cause problems. Not sure I'd have the (bulletproof) balls to follow Bringmyfix's advice, I take my hat off to him.

alloy and steel probably welded together, Your solution is coca cola in the seat tube. Really.
Just por loads of Coca cola and leave the bike upside down overnite, try again in the morning.
Good luck

drunken wrestling didnt work do you think throwing it off my 18th floor balcony might loosen it up?

Another often stated but hard to do solution is Ammonia (reacts with the oxidisation that causes Alu to stick in steel frames).

Downsides of this technique:
1) Hard to get Ammonia these days
2) It stinks and is dangerous (so you have to do it outside).
3) Its messy as its hard to get the Ammonia in the right place (often times have to pull BB, flip bike over and pour down seattube. Leave to soak overnight etc.)

I can't believe though that someone didn't post this: 15 Ways to Unstick a Seatpost - by Sheldon 'Crazy beard' Brown. If one of these doesn't do it then you're *******. (Has many of the suggestions above but still good reading).

don't bother with WD40 etc. i used a whole can of GT85 to no avail, got some plusgas, run it down the inside, left overnight, popped out straight away. The stuff is amazing.
or leave it in there and give me the supertype,
i've been looking for one for ages...
go on you know you want to ;)

pip Another often stated but hard to do solution is Ammonia (reacts with the oxidisation that causes Alu to stick in steel frames).

Downsides of this technique:
1) Hard to get Ammonia these days
2) It stinks and is dangerous (so you have to do it outside).
3) Its messy as its hard to get the Ammonia in the right place (often times have to pull BB, flip bike over and pour down seattube. Leave to soak overnight etc.)

I can't believe though that someone didn't post this: 15 Ways to Unstick a Seatpost - by Sheldon 'Crazy beard' Brown. If one of these doesn't do it then you're *******. (Has many of the suggestions above but still good reading).

coca cola and amonia are pretty much the same thing...basic solution, as in opposite to acid. ;-)

Coca cola is acidic...

Edit: The CO2 canister idea that Sheldon Brown mentions seems like a good idea. Those canisters get sooo cold.

In the worst, worst, worst case, try caustic soda - before you try hammer/vice and end up like this :

Kept the seat on mine to use as a lever... It just pulled the saddle of the rails!!! Think i'll try the coke trick tonight!!! If that fails, guess i'll have to try Sheldons careful cutting technique!

This guys had to heat.
Bye bye paint.

http://www.bikeforums.net/showthread.php?t=228880&highlight=seatpost+stuck

hmmm miche supertype nice

ahhh we had great fun with a seized seatpost on our trip to paris - tried wrestling it free on a french roadside - even 4 people couldn't get the fucker loose... My friend ended up banging the thing against the pavement but it wouldn't budge! luckily we found a guy with a huge wrench so it all worked out in the end - know anyone with a huge wrench??

Guess it's a trip to the LBS to see if they can do anything, tried the coke trick... Still stuck fast. Since the saddle broke off and mangled the top I cut it down to get a look inside (and pour said fizzy in) looks clean, so guess it just needs some big grips on it... Maybe they can get the BB out too? Brick lane is my nearest shop, how are they for workshop stuff?

same thread alternative method (worked for me) on Moving Target

here

tomiskinky Guess it's a trip to the LBS to see if they can do anything, tried the coke trick... Still stuck fast. Since the saddle broke off and mangled the top I cut it down to get a look inside (and pour said fizzy in) looks clean, so guess it just needs some big grips on it... Maybe they can get the BB out too? Brick lane is my nearest shop, how are they for workshop stuff?

If you've already trashed the post - what about drilling through it and twisting it around with a screwdriver through the hole? It might untwist or shatter the tube.
Either way it's out. NB: I've not tried anything like this myself. Beware. Warning. Alert. Etc.

I did think about the drilling idea myself, but the post is pretty deep in the frame. Maybe I should try plusgas, see it that frees it up?