I’ve got a steel framed single speed frame with an aluminium seat post, and the two seem to be getting on a little too well. I’ve tried GT85, chain oil, twisting, pulling and hitting with a rubber mallet.
Anyone got any good recipes or ideas for separating the two?

Boiling water.

Boiling water.

Being STW someone has to post a totally opposite suggestion 🙂

Try freezing. I had a similar problem a couple of weeks ago and got one of those kits plumbers use to freeze pipes. got it cold then put seat post in vice and twisted the frame

Are you trying to twist the seat/tube?

Clamp the seat post in a vice, then twist the frame. If you’ve not got a vice, put the bike upside down, wheels off, and stand on the seat. You get A lot more leverage. Had the same problem myself. It let go with a bang with a good twist

As per Drac – boiling water and try to pour it only on the frame (eg keep seatpost a little upright) as you want to heat that more than the seatpost. Good luck and remeber to keep it clean and lubbed in future 😉

Upside down, bottom bracket out, sodium hydroxide down the seat tube, dissolve the aluminium oxide that has cause it to become stuck. However, dint under estimate just how nasty that stuff it.

Other option, cut the post and use an adjustable reamer to remove post from the inside.

My favourite, time machine and a tub of coppaslip.

There is a chap who specialises in this, send him the frame and they come apart by magic.

I would try the following in this order:

1. Vice and use the frame for leverage

2. Penetrating oil, keep soaking for a few days and try again

3. Caustic soda but as above its nasty

If boiling water doesn’t work caustic soda will. Sometimes can take a couple of days. Might scrap the seatpost but the frame will be fine.

Aluminium contracts and expands more than steel. So freeze it, then do all the pulling and twisting. Even waiting for a frost might help.

Caustic soda dissolves ALU itself, BTW, not ALU oxide.

I have a similar problem with a road bike, alloy seat-post and carbon frame though. Also to complicate matters, the seat-post is not round, it is shaped (as is obviously the frame). Will have to ry the freezing route and maybe oil at some point.

You have my sympathy OP, same thing here recently. I spent hours on most if the options above by which time I had developed a deep loathing for a previously trusted seatpost. In the end I did the caustic soda thing; it took 2 hours, worked perfectly and had the added bonus of being a great therapy as the damned seatpost dissolved to nothingness before my eyes.

Feel free to email for tips on the process. It’s dirty, gassy and probably a bit dangerous. Get kitted up properly and get it over and done with!

Before you go down the caustic soda route try using Coca Cola. Turn the bike upside down, plug all the holes in the frame ( so that the coca-cola doesn’t run out). Orientate the bike so that the seat tube is vertical then, using the holes in the bottom bracket shell, fill the seat tube all the way to the top with Coca Cola. Leave to soak for approx 48 hours, re-checking periodically to ensure that the seat tube is filled all the way to the top.

After 48 hours (or thereabouts) empty the coke from the frame (messy!), rinse out well, then put seat pin in vice or similar and twist. The seat pin should then release.

Buy large tub of copper grease, use a reasonable sized splodge of it to lubricate the new seat pin…or the old one depending what damage you did it trying to release it, and re-insert into frame.

I’m not going to claim any great idea expertise in chemistry past A-level but I was under the impression that alu oxide could behave in an acidic way and therefore react with a base (sodium hydroxide) but happy to be corrected if wrong.

http://www.chemguide.co.uk/inorganic/period3/oxidesh2o.html

But this thread is about seatposts, not chemistry so probably best not to derail it.

There are many videos online. These dudes show how to do it properly and safely, Walter White style.

how to cook a seatpost

Or simply get the expert to do it saving all that faff and risk to your nice and expensive gear.

http://www.theseatpostman.com

He did mine without any damage to the Ti frame or Thompson seat post.

Blog
http://johnclimber.com/2015/11/02/at-last-my-stuck-seatpost-is-out/

Stick an old saddle on the post then whack the nose from the side with a lump hammer. You’ll destroy the saddle, possibly the post as well but it’s pretty effective.

But this thread is about seatposts, not chemistry

Disagree, chemistry is the reason he has a problem, chemistry can solve it.

I tried caustic soda. Tested it out on ALU filings and the oxide. The filings produced the bubbles, the powder did nothing. So as above, it’ll work by dissolving the post.

Second the Seatpost man he’s brilliant, frame wasn’t marked in anyway. Totally recommend him.

Plus Merlin cycles is around the corner.

http://singletrackworld.com/forum/topic/removing-a-very-stuck-seatpost

http://singletrackworld.com/forum/topic/help-my-seat-post-is-stuck

http://singletrackworld.com/forum/topic/stuck-seatpost-1

http://singletrackworld.com/forum/topic/stuck-seatpost-what-next

http://singletrackworld.com/forum/topic/seized-ali-seatpost-steel-frame

http://singletrackworld.com/forum/topic/seat-post-stuck-in-frame-any-clever-ideas

http://singletrackworld.com/forum/topic/tips-to-remove-a-seized-ally-seat-post-from-steel-frame

http://singletrackworld.com/forum/topic/solid-jammed-aluminium-seat-post-in-carbon-road-bike-frame

http://singletrackworld.com/forum/topic/seized-seat-post

http://singletrackworld.com/forum/topic/removing-a-stuck-seatpost

http://singletrackworld.com/forum/topic/stuck-seatpost-in-a-steel-frame

http://singletrackworld.com/forum/topic/stuck-seat-post

http://singletrackworld.com/forum/topic/has-anyone-ever-really-removed-a-seat-post-with-caustic-soda

I had similar but with a stuck quill stem in a set of 1″ steel forks. Resisted everything from brute force, WD40, ammonia, a hack saw etc.

Finally cut the stem off and subjected it to a dunking in caustic soda. Took about 3 hours of this

To turn this

Via this stage

Into this

Result.

Caustic soda is nasty. Wear protective gear and eye protection.

Someone suggesting citric acid might dissolve Al oxide..

Wookster – Member
Second the Seatpost man he’s brilliant, frame wasn’t marked in anyway. Totally recommend him.

Plus Merlin cycles is around the corner.

The expense and risk of all of the above in my untrained hands was the thing that made me head ove the The Seat Post Man.
Plus also the cost of a new Thompson seatpost if I damaged it while taking it out was a no brainer

Wd40 won’t do anything but a few days of decent penetrating oil should. Wouldn’t try a vice or twisting without doing that first. Available in all homeware and diy shops