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cracked seatpost

  • This topic has 16 replies, 15 voices, and was last updated 10 years ago by chief-o.
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  • May 17, 2016 at 4:27 pm #25759
    RoadbikeRoss

    I’ve got a crack in my carbon seatpost. Does anyone know if it would be safe to swap it with the missus post as the crack would be below the clamp in her frame. Just until I can afford to replace it ? Many thanks.

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  • May 22, 2016 at 6:38 am #872039
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    chief-o

    The size and orientation of
    The size and orientation of the cracks are important. Today many manufacturers use ud carbon, which is fine, however they use it on the surface. In other industries it would be sandwiched between woven plies to avoid crack propagation. It may be that the is just a separation between fibres on the top ply. Let’s put it in context. Bikes are made in their thousands in China production lines. They do not have the same process controlled and inspection as other industries. Point is that all bike parts from carbon will have defects of some sort. Voids, wrinkles and delamination. Just need to judge how severe the cracks, if it is a cracking, is. I doubt very much that a carbon seat post would snap catastrophic.
    Post a pic and we see how it looks.

    May 21, 2016 at 8:47 am #872037
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    Canyon48

    The thing about carbon is

    The thing about carbon is once it’s got a small crack, that’s it gone really.

    Metals can usually perform fine even with cracks in them (assuming the stress is below yield stress of the material – yes obviously then you get failure due to fatuige), they just won’t last that long. 

    I woud consider the carbon seatpost structurally failed with a crack in it, therefore the bin is the only palce for it.

    I do see what you are saying though, suppose you cut it off above the crack (then treated the exposed fibres) before inseting to the original minimum insertion length, then you could reasonably consider it safe.

    May 21, 2016 at 8:24 am #872035
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    Kim Chee

    A cracked carbon post

    A cracked carbon post shearing a femoral artery or removing anyones perineum from usage (esp. your wife’s) is NOT wise! Even if the current, visible crack will be hidden, the structural integrity is GONE! Replace any carbon posts with the 

    Masterpiece Seatpost

    and ride with your mind at ease. You CAN afford it-if you want to go cheap, buy the 

    Elite Seatpost

    which is still better than anyone elses post (except for Nitto for classic bikes).  

     

    May 20, 2016 at 3:40 pm #872033
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    chief-o

    How big is the crack and in
    How big is the crack and in what direction? How much below the clamp would it be?

    May 19, 2016 at 2:04 pm #872031
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    Welsh boy

    BigMat wrote:

    BigMat wrote:

    … it is probably fine.


    I like the use of the word “probably”.
    I have just bought a Selcof seat post from planetX because my far easy carbon one cracked, £30 well spent if you ask me and a lot cheaper than a divorce/reconstructive plastic surgery.

    May 19, 2016 at 1:30 pm #872029
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    BigMat

    I’ve had a crack in the

    I’ve had a crack in the laquer to my carbon seatpost for the last 7 years, put a sticker over it and ignored it.  If the crack looks to be structural then bin it, otherwise it is probably fine.

    May 19, 2016 at 1:05 pm #872027
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    BikeBud

    Buy an alu seatpost until you

    Buy an alu seatpost until you can afford another carbon one, or an rsp carbon seatpost which are ridiculously good value.  

    May 18, 2016 at 1:12 pm #872025
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    matthewn5

    Do you actually like your

    Do you actually like your Missus?

    If you do, throw the cracked seatpost away.

    Otherwise, yeah give her a dangerous seatpost without that might impale her if it breaks without warning.

    Jeez.

    May 18, 2016 at 9:26 am #872023
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    RoadbikeRoss
    Butty wrote:
    listerine wrote:
    Not a good idea – the crack could propagate.

    But it’ll be OK as it will be on the Missus’s bike

     

    i only asked as the crack would sit below the clamp on her bike. 

    May 18, 2016 at 6:56 am #872021
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    Anonymous
    listerine wrote:
    Not a good idea – the crack could propagate.

    But it’ll be OK as it will be on the Missus’s bike

    May 17, 2016 at 8:01 pm #872019
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    Jack Osbourne snr

    Bin it.
    Bin it.

    May 17, 2016 at 5:55 pm #872017
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    listerine

    Not a good idea – the crack

    Not a good idea – the crack could propagate.

    May 17, 2016 at 5:40 pm #872015
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    stevenagesteve

    Assuming the post of the same
    Assuming the post of the same size, I’d still say that posts have a minimum insertion point for a reason. Although the clamp stops movement in two planes doubt it absorbs all the flex forces. And do you want to explain who is at fault to your wife if it breaks whilst she is on it…

    May 17, 2016 at 5:11 pm #872013
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    Grahamd

    Depends on whether your

    Depends on whether your missus knows beforehand…

    May 17, 2016 at 5:06 pm #872011
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    mike the bike

    You do love to live

    You do love to live dangerously don’t you.

    Why not get a short length of wooden dowel and jam it up the seat post, this will put your mind at rest until you can get a new one.  Incidentally, Planet X sometimes have decent seatposts at very attractive prices.

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