spining a seat post clamp 180 for a carbon seat post
07-02-15, 11:56 AM
#1
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spining a seat post clamp 180 for a carbon seat post
i have heard that you should flip a seat post clamp 180 of where the frame has the ears when using a carbon post. does this serve any purpose or am i ok lining up the seat post clamp ears with the frames ears or will it dig into my seat post? thanks in advance
07-02-15, 12:12 PM
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Yes, it serves a definite purpose, though moving it 180° isn't necessary. When you tighten a clamp it wants to dig in at the ears rather than spread the tension evenly all the way around. Moving the clamp so it's slot is not aligned with the frame tube allows the tube and clamp to buttress each other and prevent the local stres concentration that would happen if the slots were aligned.
The tube supports the clamp at the ears so it can't dig in, an likewise the continuous clamp band doesn't allow the tube to dig in at the slot. Any misalignment of the slots of more than a few degrees accomplishes the same thing as rotating the band 180°, and many newer bands are already made with the lot offset from center for that reason.
BTW- it's critical that you grease between the clamp and tube when doing this so the band can slide on the tube as you tighten. Otherwise friction will keep the band from closing the tube at the slot and you'll have much less gripping force on the post compared to clamp bolt pressure.
The tube supports the clamp at the ears so it can't dig in, an likewise the continuous clamp band doesn't allow the tube to dig in at the slot. Any misalignment of the slots of more than a few degrees accomplishes the same thing as rotating the band 180°, and many newer bands are already made with the lot offset from center for that reason.
BTW- it's critical that you grease between the clamp and tube when doing this so the band can slide on the tube as you tighten. Otherwise friction will keep the band from closing the tube at the slot and you'll have much less gripping force on the post compared to clamp bolt pressure.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
“Never argue with an idiot. He will only bring you down to his level and beat you with experience.”, George Carlin
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
Last edited by FBinNY; 07-02-15 at 12:17 PM.
07-02-15, 01:01 PM
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You don't have to rotate it 180 degrees, just a small amount will do, as FB indicates. I have seen collars with position markings for metal and carbon posts and they are about 15 degrees apart.
07-02-15, 10:06 PM
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So for the clamp i just need to spin it just enough that the ears of the clamp arent on the frames ears or 15 degrees,And add grease? Thanks for your guys answers carbon seat post are a new thing for me and couldnt find much about clamp oreintation
07-02-15, 10:12 PM
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I clamped on the "ears" (never heard that term before, ... new every day), for a decades on my bikes and never once had any issue with clamps. I didn't hear much about clamp problems either. 50 years of riding.
07-03-15, 04:37 PM
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Spin it all the way 180 degrees for all the reasons listed here and you'll approve of the aesthetics more if it's lined up with your top tube. You'll continuously be looking down at it and thinking it looks stupid if you just rotate it some to the side.
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