Seized Seatpost - Revisited

I have a 1999 Trek 930 with a seized seatpost.

I've tried everything from using hot water, soaking it in diesel fuel, soaking it vinegar and lemon mix and finally heating up the post with a torch till the vinegar was boiling inside the tube turned upside-down. Then I'd dip only the post into a bucket full of ice water. It won't spin. The seat clamp is still there and I've used it to latch a long pipe in attempt to twist it. Again, no success.

So I'm thinking of using caustic soda as shown in this video: https://www.youtube.com/watch?v=-dYnSVVDxrE

However, I need to know if the frame is steel or otherwise the caustic soda will eat through it too (in addition to the seatpost).

Do you know guys know if the frame is steel?

Or maybe any other ideas for removing this stuck seatpost?

Thanks,

You can see if your frame is steel by seeing if a magnet will stick to it.

If it is, remember that you *will* need to remove the bottom bracket before applying caustic soda.

Personally, I'd try hitting it with a slide hammer first. Caustic is effective, but it's pretty unpleasant / dangerous to deal with..

Another option, which *might* work, might also destroy the whole shooting match, is to electrically heat the corrosion that's blocking the seatpost. This is done using a welder, -ve connected to the seatpost, +ve to the frame, maximum amps, turn on, wait 2-3 seconds, turn off, wait a couple of minutes, repeat as necessary. Works a treat for loosening steel studs corroded into / snapped off in alloy engine blocks, but I have never tried it on a bike. Basically, it "burns out" the corrosion.

Hmm, I don't have a welder, so that option is out, and to be honest I don't have a slide hammer and I don't know if it's worth purchasing one.

I did try something similar - I connected a hoisting rope with a rachet and cranked it till the rachet gave up which about the time I couldn't crank anymore... all to no avail. Yeah, I really didn't want to go the caustic soda route...

I put mine in a vice horizontal drilled a hole in seat post and put a bolt though it then wrapped a ratchet strap around the bolt and hooked the other end on the the concrete wall , tightened it up and heated the seat tube up.

I did the same with seized forks to

Watching with interest. Got one soaking............

The History Man":3pfai4tl said:

Watching with interest. Got one soaking............

Click to expand...

In what and how long?

In steel overbury's and over a week.

Re:

Did mine with caustic soda. £3 odd from b&q. Cut the seatpost off fairly flush with the frame. I taped up all the holes, including the stays and bottom bracket (old innertube), taped the seat tube to protect the paint as much as possible. Mixed my potion in an old plastic bottle. Add the caustic to water, not other way around, you will feel the bottle getting hot! With goggles and merrygolds fill the seat tube and watch the magic happen. Also eats all rust away.

Anyone who can be bothered to send/bring frame, I would be happy to do it for them.

npn":39b8wnjx said:

I have a 1999 Trek 930 with a seized seatpost.

I've tried everything from using hot water, soaking it in diesel fuel, soaking it vinegar and lemon mix and finally heating up the post with a torch till the vinegar was boiling inside the tube turned upside-down. Then I'd dip only the post into a bucket full of ice water. It won't spin. The seat clamp is still there and I've used it to latch a long pipe in attempt to twist it. Again, no success.

So I'm thinking of using caustic soda as shown in this video: https://www.youtube.com/watch?v=-dYnSVVDxrE

However, I need to know if the frame is steel or otherwise the caustic soda will eat through it too (in addition to the seatpost).

Do you know guys know if the frame is steel?

Or maybe any other ideas for removing this stuck seatpost?

Thanks,

Click to expand...

I wouldn't trust the guy in that video

But yes, your Trek 930 frame will be steel, so it is doable. Just bear in mind that either you will have to be very careful not to splash it on the paintwork or it will need repainting afterwards.