Seatpost diameter, related to strength??

brindlescoops
brindlescoops Posts: 464
edited February 2013 in Road beginners
Hi, as we all know, seatposts come in many different sizes, but... Is a 27mm post going to be weaker then a 30.9 post for example, or are the walls thicker to compensate???
My biggest fear is that should I crash, burn and die, my Wife would sell my stuff based upon what I told her I paid for it.

Comments

  • You aint gonna break a seatpost unless its dodgy carbon. Dont worry they are all strong as hell.
    the deeper the section the deeper the pleasure.
  • MichaelW
    MichaelW Posts: 2,164
    All you can say is that a wider seatpost is stiffer than a narrower one. Most are strong enough.
    If you are a heavyweight rider then it would make sense to look for a frame with a wider seat-tube and seatpost.
  • smidsy
    smidsy Posts: 5,273
    Its irrelevant as you can not fit a 31.6 if yours needs a 27.1 etc etc .
    Yellow is the new Black.
  • nicklouse
    nicklouse Posts: 50,675
    as above. and they all need to be strong enough to do what they need to do.

    so a 27.0 will be just a strong as a 31.6 but the weights may be different (given the same material)
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • smidsy wrote:
    Its irrelevant as you can not fit a 31.6 if yours needs a 27.1 etc etc .

    I know I posted in beginners but I'm not a complete Donkey! :lol:
    My biggest fear is that should I crash, burn and die, my Wife would sell my stuff based upon what I told her I paid for it.
  • MichaelW wrote:
    All you can say is that a wider seatpost is stiffer than a narrower one. Most are strong enough.
    If you are a heavyweight rider then it would make sense to look for a frame with a wider seat-tube and seatpost.


    I'm not even sure you can say that. The larger diameter seat post will have a larger second moment of area given a certain wall thickness. This means the wall thickness of the larger diameter post could potentially be reduced to achieve the same stiffness as the narrower post or a greater level of stiffness could be achieved by maintaining the same wall thickness as the narrower post. All of this has to be traded off against the final weight of the seat post and the ability of the post to withstand the compressive forces of the riders weight pushing down.

    At the end of the day, I suspect there isn't and significant difference between the two diameters of posts mentioned.