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I have an old steel frame (Columbus Number 2 I think) that has the seat post (Suntour Superbe Pro - see, I said it was old!) rusted in. I have tried lots of WD-40 but it will not budge.
Any tips on how I can get it out without having to cut the frame up?

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related: instructables.com/community/Ammonia--Aluminum – user652 Mar 11 '11 at 17:58

8 Answers

up vote 13 down vote accepted

Before you take any more forceful measures, it may be a good idea to think a little about chemistry:

  • 'Rust' is typically the name put on any type of corrosion, but technically & specifically, it is the corrosion of iron (or steel) to form iron-oxides.
  • Although your bicycle is most definitely steel, your seatpost is not -- it's aluminum-alloy, which does not 'rust', but definitely corrodes (creating aluminum oxide).
  • WD-40 is a penetrating oil which is designed to, amongst other things, break up iron-oxides. However, it is pretty much useless against aluminum-oxides, especially when they have already corroded & bonded.
  • Ammonia, however, is spectacularly good at eliminating aluminum-oxides.

Therefore, if WD-40 isn't doing the trick, get some ammonia, apply it in a similar fashion, and let it sit. It may just be all you need!

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This is a very cool tip. You might want to clarify alloy = "aluminum alloy" in this case. If it's an iron alloy (e.g. chromoly) then ammonia won't work. – darkcanuck Aug 30 '10 at 17:49
@darkcanuck Duly noted & edited. Thanks! – Dustin Aug 30 '10 at 18:47
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Is it dangerous that this will destroy the bike? Are there any risks involved with this? – sixtyfootersdude Jan 14 '11 at 23:41
Oxalic acid (sold as "wood bleach" at paint stores) will "reduce" rust (iron oxide). – Daniel R Hicks Jan 13 '12 at 12:22
up vote 9 down vote

This is a tough one. It's not impossible but you really need mechanical advantage. If you can clamp the seatpost, you will get the best chance at freeing this. You will probably damage/lose the seatpost with this method.

  1. Make sure the seatpost is free of grease and oil on the outside.
  2. Turn the frame upside down and clamp the seatpost into a bench vise.
  3. Spray WD-40 into the seattube from the bottom bracket opening.
  4. It will probably be dripping rusty colored oil out the top of the seat tube (which is now facing the floor - you might want to put something to catch the oil under there.).
  5. Carefully hold the head tube and the rear stays and try to rotate the frame on the post.
  6. Work it slowly and carefully being sure not to bend the stays!*
  7. Make sure the seat post is not rotating in the vise (if so, clamp tighter)

This process can take some time. You will need patience and lots of WD-40. Eventually, the post will rotate in the seat tube and you will be able to work it out.

*The trick is knowing how much force to apply. Sometimes you need more than you think and sometimes you apply more than you need (which results in unwanted damage). This difference comes with experience.

Oh and also: grease the new seatpost well before you put it back in - you'll appreciate it later.

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"be careful not to bend the stays" You're right, so I think it is better to do that with a rear hub or even wheel tightly attached in place. And have you considered 44-16? I love it! ;o) – heltonbiker Oct 6 '11 at 18:07
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Alternatively you could bore a hole trough the upper part of the seatpost, poke a large screwdriver or another bar and apply torque to the seatpost in order to make it spin. This has done the trick for me when I had the bike assembled or didn't had a vise. You may need somebody to help you to hold the bike or frame. – Jahaziel Jan 13 '12 at 20:22
up vote 5 down vote

Untested and at-your-own-risk, but this is what I would try:

  1. Soak the rusted join with WD-40 from above and below (ie. flip the frame and spray down the seat tube). Let it sit for a few hours or overnight.
  2. Secure the frame against something solid, like a heavy workbench (not a repair stand!).
  3. Put an old saddle you don't care much about on the seat post.
  4. Hit the side of the saddle's nose with a hammer or mallet. Use short, hard taps -- using wild swings you're liable to hurt yourself or the frame.

The idea is to use the torque of the saddle to break the bond between the post and the frame. You don't need to move the post much. If the post moves, then you should be able to work it loose without the hammer. If it doesn't, then worst case you've destroyed an old saddle.

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up vote 3 down vote

Cut the top off of the tube then carefully use a hacksaw blade inside the seat post to cut toward the seat tube. A handle for a hacksaw blade works or just wrap the plain blade with a bit of tape to make a handle. You should then be able to free the old seat post.

Or does the seat post extend way down into the frame? Even then this should help as the WD-40 will get a better chance to reach the lower parts.

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Ouch! I was hoping to be able to save the seat post as well if possible. I might have to sacrifice it in the end. – Anthony K Aug 30 '10 at 14:38
Your seatpost is already most probably gone. Give up on it and save the frame at least! (but of course, you might end up saving the post...) – heltonbiker Oct 6 '11 at 18:09
up vote 2 down vote

I had this problem with a very stubborn seat post (turns out there was a wedge in it to keep the post in).

One thing that I tried was putting a blow torch on the frame to try and expand it a bit to get the post out and loosen any corrosion. I would only try this after WD40 has failed.

Disclaimer: this may damage your bike

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2  
Aluminum expands more than steel, so the nowadays recommended method is to plug the lower hole of the post and drip liquid nitrogen inside (might burn your skin! way cold!). Another option would be to empty a CO2 cartridge inside the post (or a lot of dry ice in alchohol) and THEN to wash the outside with boiling water. But never heat alone. – heltonbiker Oct 6 '11 at 18:11
@heltonbiker - this method is described by Leonard Zinn – memnoch_proxy Jan 13 '12 at 5:11
Heat alone can work, if you actually resort to enough of it to melt the aluminium. Obviously you need to be cautious, and your bike will need a repaint afterwards, but some framebuilders will do it: forum.ctc.org.uk/viewtopic.php?f=25&t=16716 yacf.co.uk/forum/index.php?topic=36893.msg771842#msg771842 – armb Mar 20 at 12:23
up vote 2 down vote

You should check out the 15 Way To Unstick a Seatpost by Sheldon "Unggggghhh!" Brown

http://www.sheldonbrown.com/stuck-seatposts.html

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I tried them all. Still fighting. But don't give up, folks! (major problem: ammonia does not penetrate already oiled parts...) – heltonbiker Oct 6 '11 at 18:12
I recently got a stuck aluminium seatpost out of a steel frame using the sodium hydroxide method. Took quite a while, but it did eventually dissolve it. I spent some time with drills and hacksaw blades first - it was a long thick seatpost. – armb Mar 20 at 12:11
up vote 1 down vote

there is aerosol spray available at most hardware stores called PB Blaster it is much more effective when dealing with rust than WD=40

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up vote 0 down vote

Try put your seatpost / saddle on the vise ( reverse the bike ) then rotate the frame for pulling out the seatpost, put WD-40 or other lubricant for before you do it....

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