How to Remove Aluminum Seat post Stuck in Steel Frame

If you have had an unused bike for a very long time, or you have attached a seat post to a different kind of bike’s steel frame, then the chances are that the seat post will be stuck in the steel frame.

You clearly need to be aware of this scenario, as removing a stuck steel post is incredibly tedious. It requires a lot of hassle and time to get it removed.

I have a colleague who almost stopped using his bike due to the aluminum Seatpost getting stuck inside the steel frame. The height and the saddle made it uncomfortable for him to use.

Now let us talk about some of the tips and hacks to remove your aluminum Seatpost. 

Why is your Aluminum Seat Post Stuck in Steel Frame?

Aluminum Seatpost stuck in steel frame

Before approaching the ways to fix issues, it is essential first to identify why it has happened in the first place. So, before closing to troubleshoot, you may have to determine why your Seatpost has become stuck.

Because identifying the problem will make it easier for you to get a fix. Usually, an aluminum Seatpost gets stuck mainly for a few reasons, a couple of which are 

  • It could be a mechanical problem. Like, an oversized Seatpost has been attached to the frame with force. 
  • Or, the issue can be caused due to chemicals like erosion due to lack of usage and maintenance. 

Usually, for you to get a solution, the key should be to heat the frame, let the steel expand, and cool the aluminum to allow it to compress.

Now, as we go forward, we will dive into some of the tips to get your aluminum Seatpost out of your steel frame. 

How to Remove Stuck Seat Post from Steel Frame

1. Ammonia

Aluminum seat posts or your bike with an Aluminum Seatpost are prone to corrosion if it’s not taken care of from time to time and if it’s left out. Making the Seatpost stuck to the point that it’s completely unmovable.

Now, what you can do is get Ammonia liquid. Ammonia dissolves aluminum oxide. So, you should get ammonia and put it into the attached part of the seat post, and the frame. Then, keep the bike upside down for a couple of days, and it should get loosened. 

2. Heat Gun

If you are unable to do much about the aluminum Seatpost, then you should probably focus on the steel frame. You might want to consider getting a heat gun for this method. Heating the steel frame will cause the steel to expand, making it easier for you to open, but you have to be careful while heating as it might damage the steel and the paint.

Also, you must be careful to not heat the aluminum post. Because if Aluminum is heated accidentally, it will make your life even harder. Aluminum and titanium in general, get expanded more than steel when heated. 

3. Pipe Wrench

For this method, you may be able to get at least some form of movement to your aluminum seat post. You must need a get a pipe wrench and penetrating oil also the ammonia liquid. Put the penetrating oil into the area where the seat post and the frame are attached, then try to move the seaport with your pipe wrench.

You get a fair bit of movements, a trial and error process is required, and after multiple tries, you should get some form of movement. But, even after trying, if you still don’t see any movement, you should use ammonia liquid and try again. 

Keep in mind that you must not simply put penetrating oil and do nothing as penetrating oil will expand your Seatpost. The process in total requires penetrating oil but not just the penetrating oil.

4. Apple Cider Vinegar 

I have heard from one of my friends that Apple cider vinegar does the trick in removing the stuck Seatpost from the steel frame. Apple cider vinegar eliminates rust from steel materials like screws and bolts.

So, you might want to get apple cider vinegar from your local grocery store. Put the apple cider vinegar around the attachment all around, and then let it soak overnight.

In the morning, you might see that the attachment has become loosened. With some twists and pulls, your aluminum Seatpost should finally be opened. 

5. CO2 Cartridge 

In this method, the key is to cool the aluminum seat post. And, to do that, I can’t think of any non-technical way other than getting a CO2 cartridge. Getting a CO2 cartridge might do the trick.

If it’s sprayed inside the seat post, it will eventually shrink down just enough to get it out from the steel frame. You might also get dry ice, but that might be harmful, so you have to be extra careful. 

6. Technical Methods

how to remove stuck seat post from steel frame

To try these methods, you must be cautious and well-equipped with masks and gloves at all costs. You also have been aware of the risk factors since you will be dealing with toxic chemicals that could harm your skin.

And, if chemicals are not involved, then you may need to get a few tools that are not always inside anyone’s home. 

Hacksaw blade trick 

You require a hacksaw blade in this method. To start, you have to cut the seat post off about half the post size, which is left, carefully insert a hacksaw blade into the seat post, and cut a slit in the post.

After you’ve cut the slit, use a locking plier to hold one edge of the incision and roll the seat post up inside itself, pulling it out.

Caustic Solution (Sodium hydroxide)

This is the method that is the most dangerous and requires your attention all the time. You have to be a responsible person and be sure about every component. You need sodium hydroxide and water. Together they are from caustic soda.

Before forming the soda and trying the method, you must wear gloves, masks, and clothes covering your body. You need 200 grams of sodium hydroxide power and around 500 ml of water for the proper blend. 

Cut the seat post and from the top of the tube after covering things with plastic materials. You must remove other parts of the bike if they have aluminum because caustic soda exerts hydrogen gas if it is mixed with aluminum.

Keep some spaces for the fumes to get out so that your bike doesn’t become hazardous. After 5 minutes, the solution will start to bubble up along with the gas, and in an hour or two, the seal will be broken. You finally will be able to get it out.

A lot of toxic liquid will come out, and you must be with gloves and masks while your body is covered. I’d suggest approaching this method after talking with someone or watching a few videos related to it. 

Frequently Asked Questions

Does applying the caustic solution harm the other parts of your bike?

Yes, it absolutely can. After cutting the aluminum tube then, you also need to be careful if the other parts of the bike are aluminum or not. If the solution by any chance gets attached to the different parts of the cycle, then indeed, your bike will get damaged.

Does putting penetrating oil in the seat post help detach the steel frame?

No, it doesn’t. Instead, it only makes your situation is removing it difficult as penetrating oil expands aluminum. You require something that will compress the aluminum seat post, like a CO2 cartridge. 

Are there any alternatives to the heat gun to expand the frame?

Yes, there are. Not having a heat gun is actually quite normal for any people living in the urban and suburban areas. You can try using a propane torch or blow dryer as alternatives.

The propane torch’s flame is quite overflowing and expands if it’s sprayed onto something recklessly, so be careful not to accidentally heat the aluminum rod.

You will expand the aluminum rod if it’s heated. Basically, you’ll increase your work and make it tiring. Usage of blowdryer is relatively easy as the hot air can’t be controlled with the meter installed. 


I hope now you are pretty knowledged about what to do when an aluminum seat post is stuck in a steel frame. There are many ways to fix this issue. Some are technical, some must be done carefully, some require patience, and some are pretty easy to do. If you try the ways I have suggested to you, I believe you will indeed remove your seat post. 

Thus, I believe the next if you see your friend or someone you know has an aluminum seat post stuck in a steel frame. Then you surely will step up to help. 

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