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I am helping a friend fix his bike that he got for free. Everything went well, except that I cant raise the saddle. The seatpost is really stuck in the frame.

The clamp was easily removed. When I tried to turn the saddle only the saddle itself is turning, and the seatpost remained stuck. I tightened the saddle bracket as hard as I could, and I managed to turn the seat post a few millimeters back and forth. But somehow it is even more stuck now and I can't move it at all. I am afraid that I will bend/break the bracket in the seat if I tighten it anymore.

I tried with a pipe wrench and still couldn't twist it. Perhaps I will be able to if I have another person holding the bike so I have two hands for the wrench. I did manage to damage the surface of the seat post though.

I have a few questions:

  1. How would a professional remove the seatpost?

  2. Why is it even stuck? Can this happen because of rust, or is it more likely because the previous owner hammered a 30.2mm seatpost into a frame meant for 30mm? I can see at the Wikipediaartikel (link) that both 29.6, 29.8, 30.0, 30.2 and 30.4mm are common sizes. As I don't have a precise caliper I can only tell you that it is approximately 30mm.

  3. If it is because of rust, can I polish off the rust and use the same seatpost again? If so, should I polish the post or the internal part of the frame?

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marked as duplicate by jimchristie Aug 8 '14 at 18:55

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  • Dynamite is probably the best option. (And you're right that seatposts come in a stupid array of sizes, and it probably is possible to hammer in one size too large in some cases.) – Daniel R Hicks Aug 8 '14 at 18:47
  • (It would be of interest to know the type of metal used for the seatpost and the frame.) (And I'd probably strap the frame to something solid and use the pipe wrench, after letting some penetrating oil soak in for a few hours.) – Daniel R Hicks Aug 8 '14 at 18:49
  • Now I solved my problem, and I would really like to contribute with the result, but I can't since the question is (partly) a duplicate :( – Mads Skjern Aug 8 '14 at 20:59
  • You can edit your question to insert the "answer". – Daniel R Hicks Aug 8 '14 at 21:10
  • (I upvoted you, in anticipation of seeing your "answer" edited into the question.) – Daniel R Hicks Aug 9 '14 at 1:18
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Penetrating oil (Liquid Wrench).
It may take a few days as it needs to work its way down.
Or it may free it up in a few minutes.

The risk you take with a lot of force with a pipe wrench is you bend the bike or brake off the post or get the post out of round.

You should grease the seatpost to help prevent this. If you don't bend the post then I would reuse it.

It is most likely rust. You cannot hammer in an over sized seatpost.

If you do sacrifice the seatpost and use a use a lot of force with a pipe wrench then don't have the pipe wrench close to the bike as you could get the post out of round and really jam it in there. That may have happened when you got it to move a bit and then jammed.

You have a couple comments of use heat and I don't disagree but I would hit it with penetrating oil for a couple days before I resorted to heat. Not just once. You need to hit every few hours with oil. If you do go heat then heat gun before torch.

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    Penetrating oil, time, some more penetrating oil, more time. Gentle (!) heat from a hair-dryer might accelerate the process. Don't use force you'll just damage the bike. – Carel Aug 8 '14 at 16:26
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    Agree with @Carel. Heat will definitely help, but in my experience a hair dryer won't kick out enough. You'll need a torch, and a respray afterwards. It's more effective when Al stems have seized inside steel steerer tubes (different metals having different expansion coefficients), but even with steel on steel, the seat tube and seatpost will expand at slightly different rates. This will help "pop" the two surfaces apart once the oil has done its work. – linguamachina Aug 8 '14 at 16:41
  • If using heat after penetrating oil, beware of starting a fire. Wouldn't be a big fire, but could take you by surprise and set something else on fire. – Daniel R Hicks Aug 8 '14 at 18:50
  • That's why I suggested gentle heat just to accelerate the penetration. If it remains stuck I'd saw the post off 1 inch above the collar, then carefully use a saw-blade to make a vertical slit from the inside. – Carel Aug 8 '14 at 19:17
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I had the same problem. I used vise grips and clamped down very tightly. I hit the vice grips with a hammer, repeatedly. This will jar it loose- it took me about 15 minutes. The bad news: when I did this with my bike, it left deep scratches on the post (the vice grips will come loose and need to be clamped down again).

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So, for starters, I wouldn't worry too much about damaging the seat post--it's likely that you'll need a new one anyway. Or you'll need to really buff the post off, and that will remove any scratches. Eventually, though, I would recommend getting an aluminum post, that will help keep this from happening again (see my next point).

Secondly, yes, it is almost certainly rusted together. I would be very surprised to learn that someone had forced (successfully) a 30.2mm seat post in to a 30mm seat tube. Particularly because there are no obvious deformations in either piece. However, things rusting and sticking together is very common, but perhaps not in the bike world.

So, on to the crux of the question: how to get it apart?

I think you're on to something using a pipe wrench to try to twist it free. You should also use some sort of penetrating lubricant to help get it loose. Personally I like PB Blaster, but WD-40 is similar. Spray it down, and let it soak in for a few minutes (if you have the bottom bracket off, you may try turning the bike over and spraying it in to the bottom of the seat tube, might not hurt). You can also try hitting the frame/post with a mallet to break it apart a bit.

I know this sounds like voodoo, but getting rusted stuff apart usually comes down to brute force and ignorance. And lube.

If you're really desperate you can heat the seat tube with a blow torch while you work the post loose, but that will risk blistering the paint on the frame (also lighting the PB Blaster on fire, so be careful with that).

Godspeed.

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I recommend hitting the stuck seatpost with something like PB blaster for a while. If that doesn't work, I normally stick the seatpost in a vise and try to get some leverage on it that way (this is out of order with the tips of Sheldon).

Sheldon has 14 tips for removing a stuck seat post which you can see here.

As for heating, I've found that sunlight provides enough heat in some areas to help with the process.

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