My seatpost slips- Mtbr.com
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  1. #1
    Fragile - must be Italian
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    My seatpost slips

    I have had a really hard time keeping the seatpost stable on my '03 NRS Air. The seatpost is a 27.2 Sette carbon fiber post and I am using the shim that came with the frame. The seat collar is a bolt-on Salsa.

    I was worried about torquing the seat collar too tight so I first inserted the post with moderate torque on the seat collar bolt. But I could not keep the seatpost from slipping constantly. So I tightened it up further, and it still slipped. I *finally* think it is stable, but I have the bolt really tight.

    Some people say that the NRS frame can accommodate a 30.8 post diretly and ditch the shim, but nobody makes a 30.8 carbon post. So it looks I am stuck with the shim if I want the carbon post.

    Is there anything else I should check or do? Having the bolt cranked down so tight worries me.

    Thx...Doug

  2. #2
    U V
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    first off i would take eny grease off around the post but you've probaly done that allready, if you can't get the post to stay up useing a 'normal' allen-key and hand-tight after that you've simply got the wrong post size, some post shims don't have the length to work aswell as they should and you need one atleast four inches

  3. #3
    Rollin' a fatty
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    Remove all the grease (if any) and clean all the parts (post, shim). Reinstall and tight according to Giant's recommendations.

    I've the same thing happen with a Salsa post on my VT and solved it by a little ovethighting.

    Another alternative will be to replace your carbon post with a Thomson 30.8.

  4. #4

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    An old school trick here...

    I've done this before (with a carbon post, too). Take a beer can and cut it up, and then insert a piece of the aluminum between the post and the shim, and then tighten it down. Your post is probably a tad undersized, and this may help...

  5. #5
    Fragile - must be Italian
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    No grease

    Quote Originally Posted by DiRt DeViL
    Remove all the grease (if any) and clean all the parts (post, shim). Reinstall and tight according to Giant's recommendations.

    I've the same thing happen with a Salsa post on my VT and solved it by a little ovethighting.

    Another alternative will be to replace your carbon post with a Thomson 30.8.
    My post has no grease and never had grease on it. The post was new as was the frame and shim. I inserted the seatpost dry.

    I really didn't want to get a Thompson if I can help it. They're great posts, but I *really* wanted a carbon post for the looks (to match the carbon bar).

    How much did you "overtighten" your post?

    The other poster's beer can idea is an interesting one. I never thought that the seatpost could be a tad undersized.

    Thx...Doug

  6. #6
    Rollin' a fatty
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    In my case overtighting wasn't a big deal because the post is made of metal. If you over tight a carbon post you'll break it.

    Try the beer can shim first, I've done it in the past successfully with a carbon post (LP). Also try another shim just to see if that solves the slipping mistery.

  7. #7

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    Definitely degrease FIRST.

    Oxidation and metal shavings can make an alloy post stick in an alloy frame tube which is why people will grease them. However, this is not the case with carbon and the grease can cause exactly the problem you are having. I'd pull the shim and give it a good degreasing, along with the carbon stem, then reassemble. I've got a Sette post and it doesn't slip however my frame spacer was never greased.

    Danny

  8. #8
    shaved yeti
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    I've seen this twice in the last couple of months (regardless of grease). Both cleaned up with a coke can and a little precision cutting.

    You can cut your shim two ways... shim the 30.8 shim, or shim the post. Personally, I'd shim the shim if it's a carbon post.

    If you decide to do the post.... When you cut your shim, be sure the cut ends have no burrs on them. Use a sharp utility knife or a sharp pair of scissors. The last thing you want is a shim creating a stress riser in your post.

  9. #9
    Fragile - must be Italian
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    Shimming the shim

    Quote Originally Posted by bonkey
    I've seen this twice in the last couple of months (regardless of grease). Both cleaned up with a coke can and a little precision cutting.

    You can cut your shim two ways... shim the 30.8 shim, or shim the post. Personally, I'd shim the shim if it's a carbon post.

    If you decide to do the post.... When you cut your shim, be sure the cut ends have no burrs on them. Use a sharp utility knife or a sharp pair of scissors. The last thing you want is a shim creating a stress riser in your post.
    Thanks for pointing this out. I was considering trying your shim idea but the thought of wrapping rough aluminum around a carbon post made me a little nervous. But wrapping the shim itself with the aluminum can makes sense.

    So I think I am going to try shimming the shim. As I stated on 2 occasions now, there is NO GREASE on my seatpost - never was. Both were installed by me as new.

    How wide of a strip do I need to cut? Something that is just wider than the seat collar?

    Thx...Doug

  10. #10

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    Not on my NRS.

    Quote Originally Posted by dgangi
    Thanks for pointing this out. I was considering trying your shim idea but the thought of wrapping rough aluminum around a carbon post made me a little nervous. But wrapping the shim itself with the aluminum can makes sense.

    So I think I am going to try shimming the shim. As I stated on 2 occasions now, there is NO GREASE on my seatpost - never was. Both were installed by me as new.

    How wide of a strip do I need to cut? Something that is just wider than the seat collar?

    Thx...Doug
    I'd have a heck of a time installing a aluminum can shim between my shim and the frame. It is already a very, very tight fit.

    Danny

  11. #11
    U V
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    Quote Originally Posted by slowride
    I've done this before (with a carbon post, too). Take a beer can and cut it up, and then insert a piece of the aluminum between the post and the shim, and then tighten it down. Your post is probably a tad undersized, and this may help...
    thanks for that little tip, the post on my road has allways been a little too thin for the frame for my liking and this just added what i needed

  12. #12
    shaved yeti
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    shimm'in all day long

    Whether or not you can shim the shim really depends on how well the seattube was reamed, and how tight the shim fits into the seattube. All I can say is if the 30.8 shim isn't extremely tight (and normally it isn't) you can shim it (cut a strip about 1/2" wide and 3/4" long and reduce it from there). That should be all you need.

    Like I said before, if you can't shim the shim. You'll be fine shimming the actual post as long as you use a very sharp cutting tool.

  13. #13

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    easton makes a 30.9 carbon post

    123bikes.com sells a 30.9 Easton EC70 post. I'm told that size works as well.

    http://www.123bikes.com/results.php?...ikes&cat_id=31

  14. #14
    wait a minute....
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    Quote Originally Posted by dgangi
    I have had a really hard time keeping the seatpost stable on my '03 NRS Air. The seatpost is a 27.2 Sette carbon fiber post and I am using the shim that came with the frame. The seat collar is a bolt-on Salsa.

    I was worried about torquing the seat collar too tight so I first inserted the post with moderate torque on the seat collar bolt. But I could not keep the seatpost from slipping constantly. So I tightened it up further, and it still slipped. I *finally* think it is stable, but I have the bolt really tight.

    Some people say that the NRS frame can accommodate a 30.8 post diretly and ditch the shim, but nobody makes a 30.8 carbon post. So it looks I am stuck with the shim if I want the carbon post.

    Is there anything else I should check or do? Having the bolt cranked down so tight worries me.

    Thx...Doug
    i tried everthing with my giant and ended up haveing to buy a thompson that fit without a shim.

  15. #15
    Fragile - must be Italian
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    Solved my problem

    I was going to try the aluminum-can shim idea, but I ran into a small snag -- we have NO aluminum cans in the house. Seriously...none. My beer is all in bottles and our diet soda is in 2-liter bottles.

    Instead of sheepishly asking my neighbor for a used aluminum can (or a "free" Bud Light, which I hate the taste of), I decided to rough up the inside of the shim with 180 grit sandpaper.

    I lightly sanded the top 1 inch of the inside of the shim, just to the point where the black paint was worn off. I then reinserted the seatpost and tightened it back up. And so far no slippage.

    Thanks for the beer-can shim idea. I will keep that in mind should I ever have this problem again.

    Thx...Doug

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