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Using boiling water to free up a carbon seatpost

mattyfatty1mattyfatty1 Posts: 14
edited May 2014 in Workshop
So my carbon seatpost is stuck in my carbon frame. I've seen that boiling water works by expanding the aluminium shim. But as you can see my shim is not exposed much- http://i.imgur.com/VXlZPhT.jpg

Couple of questions- would pouring the water over it as seen in the picture work for expanding the shim? And also, is there any chance of the boiling water damaging the carbon frame?
Thanks
I was using this GCN video for reference https://www.youtube.com/watch?v=54WhdrLKKvY

Posts

  • mattyfatty1mattyfatty1 Posts: 14
    Just tried the water, it didn't work... not sure what to do now.
  • sungodsungod Posts: 12,213
    if the aluminium has corroded the product takes up more volume, it could jam the post solid, in which case heating or lubricants probably won't help

    options...

    use a mild acid to dissolve the corrosion, steep it in coke (the drink, contains phosphoric acid), or vinegar

    it will take a while to penetrate, ideally you'd need a deep vessel and insert the seatpost 'upside down' into it to a depth that will ensure the sleeve is below the liquid level

    btw you may see ammonia recommended, but this would also attack the aluminium, probably not what you want

    last resort would be sacrifice the seatpost, chop it off a couple of cm above the seat tube, use a saw to notch it from the inside, then break it out
    my bike - faster than god's and twice as shiny
  • mattyfatty1mattyfatty1 Posts: 14
    This is helpful advice, thanks a lot.
    Would the coke/vinegar do any damage, structurally or aesthetically, to the frame? Because I've heard this method being used on aluminium, but not on carbon.
  • sungodsungod Posts: 12,213
    you said there's an aluminium shim, so if there's corrosion that is what needs the attention rather than the cf

    coke, vinegar etc. will not attack the epoxy resin that binds the cf
    my bike - faster than god's and twice as shiny
  • tuneskylinetuneskyline Posts: 370
    Aluminium and carbon are a big no no. Galvanic corrosion. You could try all the things suggested and as much force as you can. It nearly wrecked my carbon bike. Seat post you can replace don't forget. Swap all aluminium contact points for carbon or titanium and you will be corrosive free
  • Monty DogMonty Dog Posts: 20,614
    ACF30 is designed specifically designed to deal with aluminium corrosion. As said, the problem is due to galvanic corrosion between the bare aluminium and carbon fibre helped by water - there is a resultant aluminium oxide build-up that jams the components together. I have seen carbon frame tubes split by corrosion. Sometimes it's simply a case of cutting out the seatpost carefully by hand and then getting the frame seat-tube re-reamed. Many frames have a bare aluminium insert in the seat-tube.
    Make mine an Italian, with Campagnolo on the side..
  • Aluminium and carbon are a big no no. Galvanic corrosion. You could try all the things suggested and as much force as you can. It nearly wrecked my carbon bike. Seat post you can replace don't forget. Swap all aluminium contact points for carbon or titanium and you will be corrosive free

    Is this for real?! Hahahaha!

    Just use some carbon slip when inserting your seatpost & you'll be fine. Never gone wrong for me. Just take the post out every 6 months, clean, "re-grease" and then pop back in.

    As for getting it out now, I'd just take a saw to it and have the seat tube reamed out afterwards.
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