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Old 04-22-14, 04:03 PM   #1
techman
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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
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Old 04-22-14, 04:04 PM   #2
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Old 04-22-14, 04:10 PM   #3
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Yes. There are shims available.

Seatpost Shim Fits 27.2mm Seatpost > Components > Saddles and Seatposts > Seatpost Small Parts | Jenson USA Online Bike Shop
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Old 04-22-14, 04:14 PM   #4
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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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Old 04-22-14, 04:42 PM   #5
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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.
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Old 04-22-14, 04:56 PM   #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.

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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.
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Old 04-22-14, 05:12 PM   #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 05:18 PM.
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Old 04-22-14, 05:20 PM   #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

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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.
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Old 04-23-14, 05:16 AM   #9
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An additional downside of shims is that they tend to creak annoyingly.
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