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  1. #1
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    Bolt in seat-post rounded.. CF seatpost

    Hi - My bolt in the seat-post to my seat is rounded I did it up to tight and now rounded it and I can't undo it. The seat-post is carbon fiber and I have the slit in the middle off the seat if this helps. What are the ways of getting it undone again? My seat is causing me problems below so need some quick fix thanks.

  2. #2
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    I assume that you mean the seat binder bolt. THat is the bolt that holds the clamp to the seat rails. If this is the case I recommend removing the seat post form the frame and then drilling the head off the bolt. you can then use a vise grip pliers to remove the bolt shank form the clamp. Go to you favorite LBS and have them get you a new bolt or have them do the work for you.

    THere is a reason that they put torque specs on bolts. You just learned why.

  3. #3
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    old allen wrenches get rounded off, try a brand new allen wrench, or get a slightly larger size allend wrench, and file it down a bit and then tap it into the rounded allen bolt head...maybe you will get lucky

  4. #4
    Senior Member CACycling's Avatar
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    Easy-out might do the trick.

  5. #5
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    From reading this, take it that it is the seat post to saddle bolt, not a frame to seat post!

    Would be useful to know the model of the seat post, but normally those bolts are steel, and are pretty strong, so shouldn't round out.

    Can you post a photo of the parts which you are having issues with?

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  7. #7
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    Ok, so it's the seat post, not the frame, don't know how you have rounded that out, unless it was Aluminium; am also wondering how much damage has been done to the saddle rails, they should be round, they look pretty squashed, as though the bolt has been clamped down for too much.

    As that bolt is effectively written off, can you use say a Torx driver which is over the size of that bolt, to hammer in, and then wrench out?

    If not, would consider cutting the sliding part of the seatpost (the head), so that the saddle could be extracted without any further damage, but this would be a destructive method, destroying the seatpost.

    If the seatpost rails are squashed (they look like it), would consider this a learning experience, bin the seatpost / saddle, and replace with new.

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    Use a Dremel tool or equivalent to cut two slots (min 2.5mm deep) on that bolt. Now use a big flat blade screwdriver to remove the bolt. Be sure to soak the threads with penetrating oil to facilitate removal.

  9. #9
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    The rails are 100% fine its just the angle when I took the photo. Seat and seat post are fairly new.

  10. #10
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    Like the Dremel idea, but there doesn't look to be too much space for error in there if any.

    Have you tried asking at a LBS to see if they have any suggestions?

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    Senior Member Chombi's Avatar
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    Buy a "screw extractor" bit form a good hardware/tool store. It's a bit that bites into stripped screw heads as you turn it counter clockwise. I'd try to do this first before trying to dremel little slits on the allenhead bolt head as I agree, that it will be hard to do so without possibly damaging the seatpost bolt hole edges. Take the post with you to the hardware and they can help you get the best size extractor for the job. You will have to replace the allen head bolt with a new one of course as the extractor will further bung up the socket on the bolt.

    Chombi

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    Hi - ok I've got it apart the problem now is my seat post has a crack in it. I'm not sure if its really a crack it looks more of a chip but hasn't fully chipped if anyone knows what I mean?

    Some pictures It maybe impossible to see as I couldn't really get a good picture but here they are. Not sure if its safe to use it I asked my LBS and they were not sure either they said carbon seat post are sometimes reinforced but mine isn't. And I don't really want to put it to waste as it cost 40


    EDIT - second picture is impossible to see, first picture is probably the best.








  13. #13
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    If that crack starts to propagate, it could fail real quick, and you may end up on the road.

    As advised, this area looked tight, and you have proved this; take this as a learning experience, and get a new seatpost.

    Good luck in getting a new Carbon post for 40, as most decent ones start at 70+; all you will get for 40 is a Carbon Wrap post

  14. #14
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    Quote Originally Posted by merlin55 View Post
    old allen wrenches get rounded off, try a brand new allen wrench, or get a slightly larger size allend wrench, and file it down a bit and then tap it into the rounded allen bolt head...maybe you will get lucky
    Torx head drivers work well for this.
    Il faut de l'audace, encore de l'audace, toujours de l'audace

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  15. #15
    Senior Member cyclist2000's Avatar
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    I can't see the crack but I think that is pretty irrelevant. The failure of a carbon seatpost can be too severe to take any chances. get a new seatpost.
    I don't do vintage, I bought them new, rode them, kept them. Now they are just old bikes
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