Stuck seat post

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Johnocyprus
Posts: 159
Joined: 13 Jan 2008, 4:12am

Stuck seat post

Post by Johnocyprus »

I have a alloy seat post in a metal frame which refuses to budge. I’ve tried penetrating oil, ice and boiling water to no avail.
The seat post is in two sections and if you bash the saddle with a mallet the top of the seat post will move however the bottom of the seat post is still fixed. I’ve researched Sheldon Brown etc and would like to would like a specialist to sort this as I don’t want to damage the bike.
There’s a guy in Lancs who has specialised jigs and will do the job for £80 which I’d pay but I’m far away and don’t want the faff and expense of stripping the bike and sending the frame up there. Does anybody know of a specialist that offers such a service within 100 miles of Surbiton, SW London?
PT1029
Posts: 1744
Joined: 16 Apr 2012, 9:20pm

Re: Stuck seat post

Post by PT1029 »

Two thoughts.
Did you try heat on the frame before trying to remove it? Heat here meaning enough to dry out (and so shrink) the aluminium oxide around the seat post. Contracted oxide means less tight in the frame. Heat here means not paint strippingly hot.
Assuming you want to save the frame, but are not to fussed about the seat post. Sometimes the seat will post move if only you can grip it enough - which you often can't, If you drill an M6 side hole through the seat post and put a M6 bolt through it, the bolt will stop the post from slipping round when the seat post is in the vice, so you don't need a crushngly tight grip on the seat post. You do need a feel on how hard you can twist the frame (assuming seat post in a vice), if you twist too hard you shear the seat post off leaving you with a much harder job.
Google "caustic soda seatpost" - disolves the aluminium, doen't harm the steel.
I said 2 things, actually it is three!

Any decent bike shop should (usually) manage to get a seat post out, though often due to teh variability of the job, can't give a price until it is done.
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gaz
Posts: 14649
Joined: 9 Mar 2007, 12:09pm
Location: Kent

Re: Stuck seat post

Post by gaz »

High on a cocktail of flossy teacakes and marmalade
alexnharvey
Posts: 1923
Joined: 10 Jan 2014, 8:39am

Re: Stuck seat post

Post by alexnharvey »

You might find someone local with a jig on the Facebook group? https://www.facebook.com/groups/372288659621602

Has part of the post broken off inside? I don't know how you could extract that save for dissolving with caustic soda.
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fausto99
Posts: 952
Joined: 19 Sep 2011, 10:06am
Location: NW Kent

Re: Stuck seat post

Post by fausto99 »

Johnocyprus wrote: 2 Apr 2021, 11:08am ...if you bash the saddle with a mallet...
Very worrying statement :shock: :lol:
I have a big vice attached to a big bench bolted to a wall. I’d be happy to help you but not if you don’t want to strip down to pretty much just the frame. PM me if you’re interested and NW Kent is close enough to you.
peetee
Posts: 4292
Joined: 4 May 2010, 10:20pm
Location: Upon a lumpy, scarred granite massif.

Re: Stuck seat post

Post by peetee »

You say ‘metal’ frame.
Do you mean steel, aluminium, titanium, magnesium....?
Is it welded, lugged, bonded..?
The older I get the more I’m inclined to act my shoe size, not my age.
Johnocyprus
Posts: 159
Joined: 13 Jan 2008, 4:12am

Re: Stuck seat post

Post by Johnocyprus »

Thank you for your replies and links, lots of good information there.

PT 1029 I haven’t applied heat part from boiling water ( and ice ). I really need the use of jig/ massive jack.
peewee I said “metal frame “ doh should have written steel ( welded ).
Fausto 99 Thank you for your kind offer PM on way.
Thanks again all. What a helpful forum this is.
ClappedOut
Posts: 585
Joined: 30 May 2020, 12:43am

Re: Stuck seat post

Post by ClappedOut »

A proper release agent not WD 40 as water dispersant
Hacksaw handle and cut Almost right through and peen in the post without damaging frame

Slide hammer on post with m8 12.9

Impact gun socket and m8 12.9

https://youtu.be/P-YpmDx86d0
ClappedOut
Posts: 585
Joined: 30 May 2020, 12:43am

Re: Stuck seat post

Post by ClappedOut »

ClappedOut post_id=1594308 time=1617621893 user_id=51486]
A proper release agent not WD 40 as water dispersant
Hacksaw handle and cut Almost right through and peen in the post without damaging frame

Slide hammer on post with m8 12.9

Impact gun socket and 2 m8 12.9 and a cobalt drill bit better than one in video go slow with lube drilling impact socket
rogerzilla
Posts: 2887
Joined: 9 Jun 2008, 8:06pm

Re: Stuck seat post

Post by rogerzilla »

Any chance of the last bit in English? It sounds good but something has gone wrong with the formatting, I think!
fastpedaller
Posts: 3435
Joined: 10 Jul 2014, 1:12pm
Location: Norfolk

Re: Stuck seat post

Post by fastpedaller »

I'd only use the hacksaw method as THE VERY LAST RESORT! One slip and the tube is damaged! The caustic soda appears to be a much slower/better method.
philkeeble
Posts: 10
Joined: 2 May 2016, 10:21am

Re: Stuck seat post

Post by philkeeble »

I've tried all the suggestions (except caustic) on my Reynolds 531 frame with a stuck Campagnolo aero seatpost ... with zero success. On a trip from Aberdeen to Southampton I dropped the bike off at https://theseatpostman.com and picked it up on the way home. I can't recommend him highly enough. He did a perfect job. He did warn that if you mess it up too much trying to get it out yourself (e.g. the hacksaw method) then it makes it more difficult (read expensive) for him. And if he finds you've cracked the frame, he won't touch it.

Note that using caustic is a) highly risky, b) highly messy, and c) ruins the paint job.

Phil
peetee
Posts: 4292
Joined: 4 May 2010, 10:20pm
Location: Upon a lumpy, scarred granite massif.

Re: Stuck seat post

Post by peetee »

philkeeble wrote: 6 Apr 2021, 1:01pm
Note that using caustic is a) highly risky, b) highly messy, and c) ruins the paint job.

Phil
a) Yes
b) Yes
c) Not necessarily. I had to do the same on a 753 Peugeot which was ‘in soak’ for two days and the paintwork wasn’t affected.
The older I get the more I’m inclined to act my shoe size, not my age.
rickbranton
Posts: 3
Joined: 21 Nov 2018, 5:02pm

Re: Stuck seat post

Post by rickbranton »

I’ve tried ammonium hydroxide with success. Left it in overnight.
ClappedOut
Posts: 585
Joined: 30 May 2020, 12:43am

Re: Stuck seat post

Post by ClappedOut »

rogerzilla wrote: 5 Apr 2021, 4:21pm Any chance of the last bit in English? It sounds good but something has gone wrong with the formatting, I think!
A suitable impact socket cross drilled cobalt drill bit with M8 12.9 tensile strength bolts and nylock nuts.
The two bolts through socket and tube spread load. The hammers of impact gun more chance of breaking corrosion without tube collapse.
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