Stuck aluminum seatpost---destructive removal

Discussion in 'Bicycle Repair' started by Happy Valley, Aug 2, 2011.

  1. Happy Valley

    Happy Valley Active Member

    Hopefully you never experience this because it's a real pain....aluminum alloy stuck in a steel frame, the seatpost from h3ll, lol! The galvanic action can literally 'weld' the post in place.

    Recently I picked up a couple nice vintage bikes, lugged cromoly steel frames:

    post A.JPG

    Unfortunately one of them had a stuck seatpost. I tried a number of tricks, spread the clamp lugs, nothing. Pipe wrench, nothing. Heat.....well aluminum expands 2 times as much as steel so heat doesn't help in removal but there is a trick of heating the seatpost with a torch to expand the aluminum and then letting it cool completely thereby hopefully breaking the corrosion bond. Tried heat twice, but nothing. Then the ammonia trick, ammonia supposedly dissolves aluminum oxide but it has to get down in to do any good. Again I got nothing. Only thing left was to saw it out. You saw off the post about 1/2" above the top of the seat tube and cut vertical slits down inside the seatpost with a hacksaw blade.

    post 1.JPG

    After breaking a few blades I made this: milled a slot into a 5/8" hardwood dowel and epoxied a hacksaw blade into it. I left just an 1/8" of the blade showing so I wouldn't cut into the frame.

    post 3.JPG

    A lot of work, maybe not worth it on some frames, about an hour on each slot. I've read where sometimes one slot is enough to kinda get the metal of the seatpost to curl inside itself with a pair of visegrips but in this case no go and I ended up having to cut 3 slots.

    post 2.JPG

    Finally, I was able to make some headway and get the damm thing free, loaded with corrosion.

    post 4.JPG

    Use anti-seize or grease, move them once in awhile, they can become a real pain in the neck when they freeze up like that. I hope this helps if you have a steel frame you want to keep or have trouble with a stuck aluminum seatpost in it.
    Last edited: Aug 3, 2011