Carbon Seatposts?

donnie murdo
donnie murdo Posts: 986
edited September 2009 in Road buying advice
Do you need to be careful when tightening the seatbolt with a carbon post more than an alloy one?

I'm thinking of getting one but not sure if I fancy the hassle of having to carry a torque wrench just for the occasional on-the-hoof adjustment.

Thanks,

Comments

  • Smokin Joe
    Smokin Joe Posts: 2,706
    I tighten mine the same as I do an alloy one. Most carbon posts have a 6nm limit, believe me your face will be purple if you attempt to reach that figure with an Allen key. If you use a carbon specific clamp with the smaller diameter bolt the thread will strip when you get over 5nm anyway.

    Carbon is tough stuff, manufacturers like to remind people of the safe limit because they have to take account of some one brain cell sue-happy fat yank who uses a six foot extension bar on the bit and gets three of his even fatter and more stupid buddies to bounce up and down on the end of it.
  • Monty Dog
    Monty Dog Posts: 20,614
    If you're worried, get a Ritchey Torquekey - pre-set to 5Nm, but if you get a t-shaped Allen key driver, 6Nm is no more than a twist of the wrist. I spent a few years doing mechanical assembly of components and got to know what different torque setting felt like. However, if it's a really lightweight post, over-zealous tightening can crack a carbon post.
    Make mine an Italian, with Campagnolo on the side..
  • chriskempton
    chriskempton Posts: 1,245
    Monty Dog wrote:
    If you're worried, get a Ritchey Torquekey - pre-set to 5Nm, but if you get a t-shaped Allen key driver, 6Nm is no more than a twist of the wrist. I spent a few years doing mechanical assembly of components and got to know what different torque setting felt like. However, if it's a really lightweight post, over-zealous tightening can crack a carbon post.

    +1 best tool ever - use it all the time on stems and posts (and even Ikea furniture)

    http://www.probikekit.com/display.php?code=T0019
  • maddog 2
    maddog 2 Posts: 8,114
    the carbon paste helps on some posts
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • nferrar
    nferrar Posts: 2,511
    Carbon paste and Ritchey key ftw. To the guy that said 6nm would have you purple in the face, err no it's pretty low (not trying to have a dick-swinging contest - just a warning to anyone that might read that and not have a torque wrench, 20nm is more purple face territory).
  • Smokin Joe
    Smokin Joe Posts: 2,706
    When I finally got a torque wrench (freegift with a sub to Cyclesport) I used it on my carbon seatpost because I was worried by all the scare stories about fracturing the material. Before I got to the 6nm limit on the wrench the thread stripped on the clamp, and thinking the clamp might be faulty I tried a replacement, set the wrench to 5nm and all ok, reset it to 6nm and as soon as I put pressure on it the same thing happened.

    Using the wrench on an ally post at 6nm (with an M4 bolt on the clamp) and then trying to undo it with a standard Allen key I can say that I have never tightened a metal seatpost up like that in my life. And I have checked my wrench against someone elses to make sure mine wasn't wrongly calibrated.

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