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Newbie Seatpost Query(8 posts)

Newbie Seatpost QueryI Love Shimano
Sep 27, 2001 3:34 PM
I noticed that my seatpost has gone down 2-5mm over the past 4-6 weeks. Is this normal at all? Or do I just have to tighten my seatpin?

Any advice would be greatly appreciated.

Thanks.
Slipping not normalKerry Irons
Sep 27, 2001 5:01 PM
You may just need to tighten the bolt, but it could be a poor fit, in which case you may need a shim (small piece of pop can), or to minimize grease on the post. Don't over tighten the bolt - if you still have slippage after tightening with firm hand pressure, then you have a fit problem.
Slipping not normalI Love Shimano
Sep 27, 2001 5:50 PM
Thank, will try tightening a bit. I already had some gnurling but around the post before because it slipped at lot after just 40 mins. of riding. This problem is beginning to irritate me. Thanks for your advice.
re: Newbie Seatpost Queryjacques
Sep 27, 2001 8:21 PM
Kerry Iron's reply connects with a very astute observation in Robert Pirsig's novel "Zen and the Art of Motorcycle Maintenance":

"There are only two kinds of mechanically-minded humans: those who would fix a slipping BMW handlebar grip with a piece of beer can - - and those who would stop riding their bike, order a new handlebar from BMW Germany at great cost and resume riding their bike only after having it it installed by the factory-authorized BMW dealer."
How do I use a pop can as a shim?I Love Shimano
Sep 27, 2001 10:06 PM
Never saw it that way! I'll be sure to try the shims if tightening the pin does not work. How do I do this? Do I attach the shim/pop can to the inside of the seattube or do I wrap it around the post (this does not sound right because the shim can get caught on the seat tube when trying to jam the post in)?

Any advice on this guys? Kerry?
How do I use a pop can as a shim?jacques
Sep 28, 2001 1:58 AM
It's trial and error. Cut a strip of aluminum out of a beer/pop can with a regular pair of scissors, about one-quarter inch wide by 2 inches long. Bend one end over 90 degrees to put a little tang on it so the shim cant disappear into the seat tube. Work seat post and shim down into the tube, tighten and check. If that's not enough of a shim, cut another, wider one. I doubt that you need the full wrap.

I sold a Cannondale years ago that had a 1 by 2-inch Budweiser can shim in it. Never told the new owner, even though the little tang was still visible on top of the seat tube. I remember thinking when I first inserted it "printed side against the post or against the set tube?" as if that mattered :-)
Forgot . . .jacques
Sep 28, 2001 2:12 AM
. . . to say: Insert the first trial shim vertically between seat post and seat tube. Don't think "wrap" unless you have a whopping mismatch between post outside diameter and seat tube inside diameter.
Hmmmm....JohnG
Sep 29, 2001 3:41 PM
I'd go to Home Depot or similar and get some industrial aluminum tape in 2" wide. This stuff is used for heating ducts. It's VERY strong and preety thin .... works reasonably good as shim material.

Most likely you need to use some alcohol and clean the post and frame area VERY carefully. Also, if you are using a slick Ti seatpost you may have to rough up the surface a bit.

YMMV
JohnG