How to remove a rusty, stuck steel seat post from a bike frame

I recently needed to remove a seriously stuck, rusted steel seat post from a chrome 1981 Cross Rider Pro BMX frame. The previous owner had tried to remove it by putting the seat post in the vice and twisting, but it had flattened, bent and actually created a weak point in the seat post where it had been twisted. Thankfully the post wasn’t broken off and was still intact.

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The head clamp method (I’ll write this one up another time) has worked for me before (on an alloy seat post), however I couldn’t use it on this old frame as the seat post was no longer round and straight.

The tools I needed were pretty scary (hammer, flat and pointed pin punches, and a butane torch) as my gentle options were running out. My main goal was to remove the post and save the original chrome finish on this classic old vintage BMX.

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After soaking the inside of the seat tube with WD40 for a couple of weeks, I heated the the end of the seat post with my blow torch until it was glowing red hot and smoking out the garage. I was careful not to let the heat from the torch reach the frame or chrome. To cool off quickly I hosed cold water down the inside of the seat tube from the hole inside the bottom bracket. I needed to cool the seat post first before the seat tube, to create shrinkage to attempt to break the rust seal. If the seat post end wasn’t flat I would have poured water in from the top.

Once cold I again applied heaps of WD40 into all areas of the seat tube. Then placed the frame upside down in the vice. Then to the scary bit.

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On the corners of the flat spots on the seat tube I began hitting my pointed and flat pin punches straight down as hard as possible. Carefully making sure I didn’t accidentally hit the frame. I turned the frame around and did the same on the other side.

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After about 2 dozen or more massive hits (and countless half hits) on both sides, I was about to heat and cool again, but I started noticing some very slight movement. The post was beginning to come out. I ended up shredding both sides of the seat post, but it stayed together enough to finish the job. If I had snapped the end of the seat post off, I would have flattened the next part and kept going.

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This may not be the best method, and and certainly not the only one, but this was one occasion that required some aggressive tactics, and it worked. Next time I will put an old set of cups into the bottom bracket as the vice clamp bit the frame slightly on the edges of the bottom bracket tube. But noting major.

I have another frame that needs the same treatment. If the clamp method doesn’t work I will be trying this again. Hope this post can help you.

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