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I bought an old bike. However there is one problem with it. The seatpost is stuck and I can't take it up or down ... and it's too high for me that my back hurts. It seems that the old user made it this way and I need to find a way to take it off or replace it somehow. Any ideas please?

Edit: do I have any chance with it? I need to note that when I got the bike I didn't find a screw that holds/locks the seatpost ... so I got it exactly as in the picture.

Pics for the seat.

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    Have you tried the suggestions on sheldonbrown.com/stuck-seatposts.html ? – Batman Mar 25 '15 at 17:28
  • @Batman i haven't tried anything with it yet. But I wanted to know if I have any chance with it by asking people here. Maybe by just looking at the pics someone can save me a lot of time and suggest a good trick. – Jack Twain Mar 25 '15 at 18:18
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    WD-40. It looks like it's rusted in place, and that should help break it free. – FreeMan Mar 25 '15 at 18:22
  • @FreeMan which one should I get? amazon.de/s/… and how to apply it? – Jack Twain Mar 25 '15 at 18:30
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    @armb Are you sure that is a steel frame? That look too thick for steel to me. And the rust did not necessarily come from the frame. There are exposed surfaces with no rust. – paparazzo Mar 27 '15 at 13:26
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Leaving out the back story - which is emotional - here is how I got an alloy seatpost out of a Columbus SLX (steel) frame.

I got a bunch of optimistic advice and it all failed me.

I tried:

Penetrating oil such as WD-40, Hard core penetrators like PBlaster and Kroil, Freeze spray, Hammers, and giant levers.

I was down to the last resort - sodium hydroxide, aka lye, aka drain cleaner.

enter image description here

I melted the seatpost out with drain cleaner. If you are going to do this you can't just buy drain cleaner. A lot of drain cleaners are not 100% sodium hydroxide. Get the pure stuff. This stuff is dangerous - use precautions. I wore safety glasses and huge gloves everytime I handled this stuff and I handled it a lot. This process takes time but if you persist you will get results with little more effort that the effort of mixing the lye and pouring the mixture.

What you are going to do is flip the bike upside down and pour lye down the seat tube so that it hits the seatpost and melts it from the inside. Lye is corrosive to aluminum, it does not affect steel. I cut the head off of my seatpost which in hindsight I would not do again. Seatposts are usually hollow and cutting the head off reveals an open hole which the lye runs out of. I plugged the hole with plumbers putty of all things. I also spring some leaks near the binder bolt so I plugged those with plumber putty also. Also my frame had holes in the top tube for cable routing so I plugged those also. I recommend experimenting with water to check for leaks! The water-test is also helpful to determine the volume that you want to use.

I pulled the wheels and fork off of my bike when I did mine because I did not want anything flopping around and also I wanted all aluminum away from the lye. You need to pull the bottom bracket because that is where you pour the lye. So with the bike upside down bike such that the seatpost is the furthest down, big gloves and eye protection donned, and your lye mixed according to instructions you pour the lye into the bottom bracket filling up the seatpost. Rinse out the container with water many many times and rinse your gloves many many times. At this point you can put your ear to the bottom bracket and you can hear the chemical sizzling. After a while - day or days - you will pour the lye out and pour some more in. I am not a chemist and I do not know how lye works, maybe if you agitate the stuff every few hours it works better. I just made sure to leave it in for at least a day and I never left it in for more than a few days.

Pour the old stuff out and pour some new stuff in.

Wait.

Repeat.

So about that hole which is revealed when you cut the head off of the seatpost. On the one hand this is something you need to plug constantly. Because of this you might not want the hole. On the other hand it makes draining easy. I got to where I would pull the plug over the slop sink, replug the hole, and pour in the fresh stuff.

The hole is also nice to access because you can see if the stuff is working - the hole gets bigger, gets jagged, etc. So you might want access to the hole during the melting.

Eventually you will get a nicely corroded seatpost which is still stuck in the frame. Now it is hacksaw blade time. enter image description here

Take a hacksaw blade, just the blade, and stick it into the seatpost hole and start cutting the seat post. These are long vertical cuts that run the length of the seatpost. You are basically cutting the round seatpost into pieces of pie. This is extremely tedious work and you will second guess yourself, thinking that you are sawing into the frame but eventually you will get a complete cut and you will realize that cutting the aluminum seatpost is very different than cutting steel.

Now you are making the vertical slices when you have time, and then plugging everything and using lye over the course of days and in between cutting sessions. The more mangled things get the more difficult it will be to keep the lye in the tube. Eventually pieces of the seatpost will come loose and you can pull them out with pliers. Keep going until everything is either corroded away or yanked out. What is left will be very rough. I recommend some files and then something attached to a drill, like a cylinder hone or perhaps a barrel hone:

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You use that to clean up the inside of the seatpost.

When you are done give your frame a good shake to make sure that all of the bits are out, then rinse again with water. You might take this opportunity to apply framesaver. You are ready to put everything back on, using grease liberally.

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Noone's mentioned heat to enlarge the steel frame.

First, check with a magnet to make sure the frame is steel. If its an aluminium frame, then stop now.

Remove the bottom bracket and bearings first. And remove the seat. Also remove brake cables from the area of the seat clamp.

Drill a good sized hole through the top of the seat pole, and fit a lever like a decent sized screwdriver.

Try some light warmth on the frame from a brazing torch or similar while an assistant dribbles water down the seat pole, to keep the seat pole cool and not expanding.

Assistant also pulls and pushes on the leverage trying to break the seatpole free.

Note this is very likely to damage the paint on the frame, and if you've used penetrating oils already, they may fume or ignite.

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Many of these answers are valid, but before you go through the trouble of heating your frame, using nasty chemicals, or anything else, there is a far simpler method that often does the trick.

  1. Get a dumpy saddle you don't mind bending and install it in the seat post.
  2. Clamp the saddle in a bench top vice.
  3. Using the entire bike frame as a lever, turn the bike. Doing this you may be able to break the corrosion that is locking your seat post in place.

If this doesn't work, go down the line of more extreme options like heat, chemicals, cutting and chiseling, etc... If its that bad though I would encourage you to go to your local bike shop.

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Not going to lie, seeing those pictures brought a tear to my eye. So sad how some people treat their toys, (referring to previous owner).

Anyways, this is a pretty simple fix. Easiest way to get the post outta there would be to give the whole area where the post meets the frame a healthy dose of wd40. Let it sit for a few minutes, then re apply. At this point, you should be able to jar it out of its rusted prison. Hit the front and back of your saddle with either hand, as if you were twisting the seat. You might have to hit a little hard, but the rust should give way enough for you to remove the post.

If that doesn't work, try recurring treatments of wd40 until it does.

Hopefully this helps. Good luck!

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    I think that by the time most folks are resorting to the techniques here they have pretty much emptied their cans of WD-40, Liquid Wrench, et al. – Daniel R Hicks Aug 19 '15 at 22:36
  • Well, to some extent I can see what you mean. But the reason you find the same solution over and over again is because it works. And beyond the products used, some people just might not know how to employ the right technique. – Weirix Aug 19 '15 at 22:50
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Just a thought…

Run a bolt – maybe even a high strength bolt – backwards through the seatpost clamp and put a putty knife or the edge of a heavy washer between the halves of the clamp so that as you tighten the bolt it opens the seat tube.

In a comment below, it was noted that in some seatpost clamps the threaded portion is an insert (i.e., it is not integral with the clamp) and would likely be pushed out by this method – so as you start tightening watch closely on the outboard side of the bolt, if you see paint cracking or any movement at all back off, you may have an insert and this idea won't work.

Tighten the bolt a bit, add your favorite penetrating oil (I like Kroil), try twisting the seat post. Rinse (or not) and repeat.

  • Might work, but note that in some frames the threaded portion of the seatpost clamp is an insert, and using this procedure would drive it out of the frame. – Daniel R Hicks Aug 20 '15 at 12:03
  • Interesting, I don't think I've ever seen one like that. Any chance you know where to find a photo of one or could at least describe how to recognize one? The one in this particular case does not appear (to me) to be an insert. – dlu Aug 20 '15 at 13:31
  • You'd see something sticking out of the outside end of the lug, generally it would be shiny chrome or stainless. – Daniel R Hicks Aug 21 '15 at 0:44

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