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Stuck seatpost

canoascanoas Posts: 271
edited February 2016 in Workshop
ALU seat post in Carbon frame...stuck :evil:

Tried so far.....

Extremely strong chap at my office
WD40
GT85
Penetration oil
Hot water on seat tube 10mins
Removed saddle turned bike upside down soaked in water bottle of Anomonia for 4 hours

Can anyone think of something else. Does hot water need to be poured over carbon seat tube for a recommended length of time?

Posts

  • First.AspectFirst.Aspect Posts: 3,334
    Freeze the seatpost, rather than heat the frame? I would have thought the prolonged heating would work against you. The underlying post will have pretty much equilibrated after 10 mins' hot water and will expand more than cf, which is basically plastic. Personally I'd try upending the seat post in a very salty ice bath. It will conduct heat faster than the frame and should shrink more.

    Its a long shot though.

    Another thing to try is more leverage. Its a risk to your frame, but get an old saddle, mount it backwards, use a crowbar or similar between the saddle rails.

    Ask the the strong bloke back. Close your eyes.

    After that, its n+ 1.
  • Turn it upside down and pour a bottle of coke down the seat tube
  • keef66keef66 Posts: 13,286
    Turn it upside down and pour a bottle of coke down the seat tube

    And you'll soon have a very sticky bike with a stuck seatpost.

    You'd be better off drinking the coke; caffeine plus sugar = more grunt power when you're swinging on the lever of choice.

    One tip I read on here a while ago was to remove the saddle and jam the clamp in a roadside drain so you can then twist the frame off the post. Hopefully I'll never have to try it on any of my bikes which are subject to a periodic removal / clean / relube* of the seatposts.

    * actually it's carbon assembly paste; I have a carbon bike with an alloy post and an alu bike with a carbon post, so I'm greasing neither.
  • keef66 wrote:
    Turn it upside down and pour a bottle of coke down the seat tube

    And you'll soon have a very sticky bike with a stuck seatpost.

    You'd be better off drinking the coke; caffeine plus sugar = more grunt power when you're swinging on the lever of choice.

    One tip I read on here a while ago was to remove the saddle and jam the clamp in a roadside drain so you can then twist the frame off the post. Hopefully I'll never have to try it on any of my bikes which are subject to a periodic removal / clean / relube* of the seatposts.

    * actually it's carbon assembly paste; I have a carbon bike with an alloy post and an alu bike with a carbon post, so I'm greasing neither.

    The coke will dissolve the rust or whatever has caused the seatpost to seize.

    Just using grunt and a lever can destroy the frame. it is better to remove the post without writing off the frame surely?

    And the bike won't get covered in coke as it is upside down ;-)
  • Steve-XcTSteve-XcT Posts: 267
    keef66 wrote:
    Turn it upside down and pour a bottle of coke down the seat tube

    And you'll soon have a very sticky bike with a stuck seatpost.

    You'd be better off drinking the coke; caffeine plus sugar = more grunt power when you're swinging on the lever of choice.

    One tip I read on here a while ago was to remove the saddle and jam the clamp in a roadside drain so you can then twist the frame off the post. Hopefully I'll never have to try it on any of my bikes which are subject to a periodic removal / clean / relube* of the seatposts.

    * actually it's carbon assembly paste; I have a carbon bike with an alloy post and an alu bike with a carbon post, so I'm greasing neither.

    As it happens phosphoric acid is one of the few things that can remove aluminium oxide. (The other is hydrofluoric and you definitely don't want THAT) ... so it might be worth a go though I'd use diet rather than full sugar for the stickyness....

    Before that its well worth the salted ice bucket on the seatpost though ....(IMHO)

    Could also try cut off the seatpost 2-3" above the frame then just slowly cutting the seatpost on the internal diameter with a fine hacksaw blade until its 80-90% cut through then cut a slot from the bit left sticking out to a 1/8th inch above the frame then try the ice and stick the seatpost in a vice and hope it collapses where you cut it ????


    I just checked and Park Tools actually does recommend coke!
  • Cheers. I love it when know it all keyboard legends are put in their place.
  • I have this issue on both my bikes. Tried brute force, oils, fluids...errr but not coke - that stuff is pure liquid evil so will give it a go and see if it works.

    On my bianchi, I tried brute force...just for reference the frame has never felt the same afterwards....not risking my current frame as the seat is in the right position, but, it would be useful to be able to tweak it for certain situations.
  • keef66keef66 Posts: 13,286
    Anybody out there actually used coke to remove a corroded alu seatpost from a carbon frame?

    Have a read on Snopes.com for a summary of all the things that Coke is alleged to do but in fact doesn't.
  • Steve-XcTSteve-XcT Posts: 267
    keef66 wrote:
    Anybody out there actually used coke to remove a corroded alu seatpost from a carbon frame?

    Have a read on Snopes.com for a summary of all the things that Coke is alleged to do but in fact doesn't.

    Phosphoric Acid (the stuff in coke) is used to etch aluminium .... its one of the few things removes the oxidised surface (why aluminium doesn't rust/corrode) and why aluminium can's of coke are actually coated...

    It's (from an educated guess based on chemistry) fairly innocuous to carbon and epoxy...
    Park Tools actually have it as a method on THEIR website ... and they are pretty good for stuff like that.

    It beats the heck out of splitting the carbon frame and costs a few pence to try.....

    I'm sceptical .... but I'd give it a go before potentially junking the frame....
  • sungodsungod Posts: 12,190
    if you can get some dry ice or freezer spray and can get it into the seat post, could be worth a try to see if it'll loosen it - the coefficient of thermal expansion for al is much higher than cf (how much depends on the cf layup)

    the acid in coke will dissolve the corrosion product, if it can reach it, the thin oil from the wd40 etc. will tend to prevent this, flushing with solvent first might help
    my bike - faster than god's and twice as shiny
  • Monty DogMonty Dog Posts: 20,614
    Coke will do F-all for aluminium oxide, just create a sticky mess. Get some ACF50 which is far more effective.
    Make mine an Italian, with Campagnolo on the side..
  • Monty Dog wrote:
    Coke will do F-all for aluminium oxide, just create a sticky mess. Get some ACF50 which is far more effective.

    It would be interesting to find out if it did or didn't!
  • socratessocrates Posts: 453
    Brown vinegar poured down the seat tube. Obviously have to take the chainset off first.
  • carefully cut the seatube vertically downward to the first cage mount, the seatpost will lift out.
  • With a saddle installed, invert the bike and insert the saddle between two fixed objects. Gently rotate the frame as if it were a breaker bar.
    Infinite diversity, infinte variations
  • Moontrane wrote:
    With a saddle installed, invert the bike and insert the saddle between two fixed objects. Gently rotate the frame as if it were a breaker bar.

    Not breaker bar but wingnut.
    Infinite diversity, infinte variations
  • redvisionredvision Posts: 2,515
    Admit defeat and take it to your lbs.
  • Moontrane wrote:
    Moontrane wrote:
    With a saddle installed, invert the bike and insert the saddle between two fixed objects. Gently rotate the frame as if it were a breaker bar.

    Not breaker bar but wingnut.
    I knew somebody called wingnut. Was bow-legged.
  • peterbob wrote:
    Moontrane wrote:
    Moontrane wrote:
    With a saddle installed, invert the bike and insert the saddle between two fixed objects. Gently rotate the frame as if it were a breaker bar.

    Not breaker bar but wingnut.
    I knew somebody called wingnut. Was bow-legged.

    I'll thank you to leave my physical malformations out of this discussion. :wink:
    Infinite diversity, infinte variations
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