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  1. #1
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    Seat post diameter question

    I have a Giant Cypress DX with a stock 30.9mm diameter seat post.
    There is a carbon fiber seatpost from Nashbar I'd like to get, but its only available in a 27.2mm diameter.
    Is it possible to use a 27.2mm diameter seat post in a bike that has a stock post of 30.9mm?
    Thanks

  2. #2
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    +1, while you can't just stick in the wrong post, you can use a shim to reduce the frame ID to 27.2. It's less than ideal for a number of reasons, but not seriously bad. Many frames already use bonded in shims as it is.
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  5. #5
    Senior Member mulveyr's Avatar
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    Quote Originally Posted by techman View Post
    I have a Giant Cypress DX with a stock 30.9mm diameter seat post.
    There is a carbon fiber seatpost from Nashbar I'd like to get, but its only available in a 27.2mm diameter.
    Is it possible to use a 27.2mm diameter seat post in a bike that has a stock post of 30.9mm?
    Thanks
    As other posters said, yes you can, with shims.

    But that begs the question--why? I used to have a Cypress DX, and between the suspension and wide tires, it already had a very cushy ride. On a bike that heavy, the weight savings of a carbon post would be unnoticable.
    Knows the weight of my bike to the nearest 10 pounds.

  6. #6
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    Good point, I should have mentioned that the post I want to use is a dual-bolt infinitely adjustable angle type,
    which I want to try considering that I'm having some Perineum numbness and soreness.
    I need a post with better adjustability. The carbon fiber is a plus for even better ride quality.
    I have no interest in saving weight with my seat post.

    Quote Originally Posted by mulveyr View Post
    As other posters said, yes you can, with shims.

    But that begs the question--why? I used to have a Cypress DX, and between the suspension and wide tires, it already had a very cushy ride. On a bike that heavy, the weight savings of a carbon post would be unnoticable.

  7. #7
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    here's a 30.9 with infinitely adjustable clamp design, i think. 30 seconds with google to find it.

    so many, i can't shake a stick at all of them. good luck.
    Last edited by hueyhoolihan; 04-22-14 at 06:18 PM.

  8. #8
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    Thanks for posting some alternatives. It wasn't that I was too lazy to Google.
    Just like the price, the reviews and I like working with my trusted online retailers like Nashbar.
    But It may be best to find a 30.9mm post instead of dealing with shimms. Thanks

    Quote Originally Posted by hueyhoolihan View Post
    here's a 30.9 with infinitely adjustable clamp design, i think. 30 seconds with google to find it.

    so many, i can't shake a stick at all of them. good luck.

  9. #9
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    An additional downside of shims is that they tend to creak annoyingly.

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