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Seat post clamp orientation for carbon frames

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Seat post clamp orientation for carbon frames

Old 08-17-18, 11:14 PM
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Bike Gremlin
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Seat post clamp orientation for carbon frames

Is there any consensus (rule of thumb) on seat post clamp orientation for carbon frames (and carbon seat posts). For all I know, on most metal ones, the orientation was usually with the slit in the clamp aligned to the slit in the seat tube.

With more than one slit in the seat tube, for all I know, clamp slit can be aligned with a slit in the frame, even on carbon frames with carbon seat posts.

When there is only one seat tube slit in a carbon frame (especially if a carbon seat post is used), should the clamp be oriented so that clamp's slit is 180 degrees away from the seat tube slit - no pressure concentrated at the slit, less risk of damaging the seat post and/or frame, or does it depend on the frame/clamp?

Using proper torque and carbon mounting paste, can a wrong clamp orientation cause frame damage? Can it cause seat post damage?

Anyone have some experience, useful links on the subject etc?
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Old 08-17-18, 11:21 PM
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Originally Posted by Slaninar View Post
Is there any consensus (rule of thumb) on seat post clamp orientation for carbon frames (and carbon seat posts). For all I know, on most metal ones, the orientation was usually with the slit in the clamp aligned to the slit in the seat tube.

With more than one slit in the seat tube, for all I know, clamp slit can be aligned with a slit in the frame, even on carbon frames with carbon seat posts.

When there is only one seat tube slit in a carbon frame (especially if a carbon seat post is used), should the clamp be oriented so that clamp's slit is 180 degrees away from the seat tube slit - no pressure concentrated at the slit, less risk of damaging the seat post and/or frame, or does it depend on the frame/clamp?

Using proper torque and carbon mounting paste, can a wrong clamp orientation cause frame damage? Can it cause seat post damage?

Anyone have some experience, useful links on the subject etc?
For all I know if it ever makes any practical difference in the life of any of those parts, then they had inadequate safety factors from new. And with "racing" hardware you pay extra for that, so clamp it any old way.
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Old 08-17-18, 11:36 PM
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Originally Posted by AnkleWork View Post
For all I know if it ever makes any practical difference in the life of any of those parts, then they had inadequate safety factors from new. And with "racing" hardware you pay extra for that, so clamp it any old way.
So, just for example, this "jewel" of Italian engineering is just a marketing gimmick?
(not that I'd have the confidence to trust that torque recommendation for a carbon frame and seat post)

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Old 08-17-18, 11:53 PM
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Originally Posted by Slaninar View Post
Is there any consensus (rule of thumb) on seat post clamp orientation for carbon frames (and carbon seat posts). For all I know, on most metal ones, the orientation was usually with the slit in the clamp aligned to the slit in the seat tube.

With more than one slit in the seat tube, for all I know, clamp slit can be aligned with a slit in the frame, even on carbon frames with carbon seat posts.

When there is only one seat tube slit in a carbon frame (especially if a carbon seat post is used), should the clamp be oriented so that clamp's slit is 180 degrees away from the seat tube slit - no pressure concentrated at the slit, less risk of damaging the seat post and/or frame, or does it depend on the frame/clamp?

Using proper torque and carbon mounting paste, can a wrong clamp orientation cause frame damage? Can it cause seat post damage?

Anyone have some experience, useful links on the subject etc?
I use a double bolt clamp. Clamps on both the tube and post independently. No slits so orientation doesn't matter you can tourque on the tube independently of the post.

Just remember that unless you put some type of lube on the bolt threads your tourque readings are essentially useless.
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Old 08-18-18, 12:01 AM
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Yes, definitely - mounting paste. For bolts one for metal, for seat post and clamp-seat tube interface carbon mounting paste.
But the question is how to orient seat post clamps that do have slits? Does it matter (make a difference)?
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Old 08-18-18, 12:31 AM
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Originally Posted by Slaninar View Post
Yes, definitely - mounting paste. For bolts one for metal, for seat post and clamp-seat tube interface carbon mounting paste.
But the question is how to orient seat post clamps that do have slits? Does it matter (make a difference)?
If the seat tube is slit, all of the stresses are going to be concentrated there no matter what you do. I would think aligning the slit in the clamp with the slit in the tube makes the most sense. That way all of the force of the clamp bolt goes into closing the slit, which is its whole purpose.

If you orient the clamp 180 degrees away from the slit in the tube, the clamp must slide along the tube surface as the slit closes and the diameter of the tube decreases, so you have to overcome that friction before you can start closing the slit, so the torque you apply to the clamp bolt does not really correlate to the clamping force on the post.

Does that make sense?
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Old 08-18-18, 12:58 AM
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Originally Posted by Tape2012 View Post
If the seat tube is slit, all of the stresses are going to be concentrated there no matter what you do. I would think aligning the slit in the clamp with the slit in the tube makes the most sense. That way all of the force of the clamp bolt goes into closing the slit, which is its whole purpose.

If you orient the clamp 180 degrees away from the slit in the tube, the clamp must slide along the tube surface as the slit closes and the diameter of the tube decreases, so you have to overcome that friction before you can start closing the slit, so the torque you apply to the clamp bolt does not really correlate to the clamping force on the post.

Does that make sense?
It makes perfect sense IMO. It is also the reason I think there is less pressure concentrated at the slit when the clamp slit is turned 180 degrees away from the seat tube slit. Which should be good for a carbon seat post.
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