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  1. #1
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    Are Seat Post clamps often overlooked ?

    When installing a seat post clamp, is there a proper way to align the slot? Does it matter if the frame is carbon?
    Does it matter if the frame is aluminum? How about a Carbon post, would that change anything?

    Most of what I can find states to put the clamp slot 180 degrees from the frame slot, for carbon frames.

    Aluminum frames I'm not sure if it matters.

    Is the rule always to have clamp slot 180 from frame slot no matter the frame material?

    Anyone know ?

  2. #2
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    My carbon frame has slots front and rear, so can't do 180.

    Anyway, I put mine facing the front because...I saw it like that on a pro bike...

  3. #3
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    Quote Originally Posted by factory feel View Post
    When installing a seat post clamp, is there a proper way to align the slot? If the seatpost is metal, the clamp's slot position does not matter.

    Does it matter if the frame is carbon?
    It's been suggested to position the clamp slot 180 degrees opposite the seat tube slot for carbon seatpost equipped bikes to minimize the clamp scoring the carbon post.

    Does it matter if the frame is aluminum?
    Only if the seatpost is carbon. It's all about preventing the potential to gouge the carbon seatpost with the clamp, and if the frame is metal, then the frame's slot can damage the carbon post as well. Positioning the seat clamp out of phase with the frame minimizes this problem.

    How about a Carbon post, would that change anything?
    See above.

    Most of what I can find states to put the clamp slot 180 degrees from the frame slot, for carbon frames.

    Is the rule always to have clamp slot 180 from frame slot no matter the frame material?
    It only matters if the SEATPOST is carbon. Anything else shouldn't be an issue.

  4. #4
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    From Thomson website....

    If the Thomson Seatpost Collar is used with a carbon fiber frame or with a carbon
    fiber seatpost, or both, orient slot in the seatpost collar 180º away from slot in
    frame.

  5. #5
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    Some of the Bianchis have Miche clamps which have 2 settings, one for a CF post and the other for alloy. That said, these clamps pretty much open at the rear where the slot in the CF seat tube is.

  6. #6
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    what's the idea behind orienting the collar's slot 180 degress away from the seattube's slot? Is it to minimize the cracking of the seatpost in case you over tighten the clamp?
    When I orient the collar in such fashion, I find that I need more torque on the collar to hold the seatpost down.

  7. #7
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    Quote Originally Posted by aclinjury View Post
    what's the idea behind orienting the collar's slot 180 degress away from the seattube's slot? Is it to minimize the cracking of the seatpost in case you over tighten the clamp?
    When I orient the collar in such fashion, I find that I need more torque on the collar to hold the seatpost down.
    The theory is that most clamps open towards the back ,and therefore combine with the "split" in the seat tube at the back to add additional force to the split area grabbing onto the CF post. Not a problem with an alloy post, but with CF the thought is that reversing it so that the tightening force is in front of the seat tube, there will not be exaggerated force on the area of the seat tube slot.

    Of course, there may be some Physics majors here that can dispute all of that theory.

  8. #8
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    Quote Originally Posted by aclinjury View Post
    what's the idea behind orienting the collar's slot 180 degress away from the seattube's slot? Is it to minimize the cracking of the seatpost in case you over tighten the clamp?
    When I orient the collar in such fashion, I find that I need more torque on the collar to hold the seatpost down.
    Yes. If you align the slots, when you compress the clamp, the edges can push on the slot and put increased stress at a focused area.


    Even if you just rotate it a little, it's better.
    Custom Di2 & Garmin/GoPro mounts 2013 SuperSix EVO Hi-MOD Team * 2004 Klein Aura V

  9. #9
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    Quote Originally Posted by tlg View Post
    Yes. If you align the slots, when you compress the clamp, the edges can push on the slot and put increased stress at a focused area.


    Even if you just rotate it a little, it's better.
    the theory about putting stress on the edges makes sense

  10. #10
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    I just turned all mine 180 degrees.

  11. #11
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    I have been doing this incorrectly for 45 years - on steel, aluminum and carbon frames. Yet, it has made absolutely no difference. That said, I'll spin the ones that spin.

  12. #12
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    Funny that when you look at all the photos of CF frames using CF seatposts, all of them show the clamp facing rearward. Colnagos, Bianchis. etc.Many of these do use the Miche clamp with the dual settings.

    Why aren't they selling the bicycle with the clamp turned 180d?

  13. #13
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    Quote Originally Posted by Peter P. View Post
    It only matters if the SEATPOST is carbon. Anything else shouldn't be an issue.
    Wrong

  14. #14
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    Quote Originally Posted by aclinjury View Post
    the theory about putting stress on the edges makes sense
    Yes it does but also aligning the relief of the clamp with slot whereby the seat tube slot edges don't touch is a viable practice as well.

  15. #15
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    Quote Originally Posted by GKSki View Post
    The theory is that most clamps open towards the back ,and therefore combine with the "split" in the seat tube at the back to add additional force to the split area grabbing onto the CF post. Not a problem with an alloy post, but with CF the thought is that reversing it so that the tightening force is in front of the seat tube, there will not be exaggerated force on the area of the seat tube slot.

    Of course, there may be some Physics majors here that can dispute all of that theory.
    Principle reason of course that the slot exists in the seat tube and relief in the seat clamp is to allow for reduction in diameter for clamping. If there is uneven clamping i.e. one edge of the seat tube slot pushed into either a carbon or alloy seat post, this may in fact help retain it because it creates a stress riser but it can score the seat post and degrade the seat tube. Best the slot edge is either avoided completely...or...the slot is completely covered by the clamp. Either or will work fine.

  16. #16
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    Quote Originally Posted by 11spd View Post
    Yes it does but also aligning the relief of the clamp with slot whereby the seat tube slot edges don't touch is a viable practice as well.
    I used to do it like this until I researched it. Now I put them all at 180 from seat tube slot

  17. #17
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    Quote Originally Posted by factory feel View Post
    I used to do it like this until I researched it. Now I put them all at 180 from seat tube slot
    Put them all back. Then, tomorrow, reverse order and repeat.

  18. #18
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    Quote Originally Posted by 11spd View Post
    Put them all back. Then, tomorrow, reverse order and repeat.
    Nope, not gonna do it. They’re staying. It makes perfect sense now.

    Even aluminum on aluminum are gonna be 180 now.

    I’ve seen the light !

  19. #19
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    Quote Originally Posted by tlg View Post
    Yes. If you align the slots, when you compress the clamp, the edges can push on the slot and put increased stress at a focused area.


    Even if you just rotate it a little, it's better.
    I don't have a fancy clamp like that one, so I just offset mine so that the slot in the clamp doesn't line up with the slot in the seat tube. I can't see any reason wy 180 degrees rotation is functionally any different than a slight rotation of the clamp.

  20. #20
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    Quote Originally Posted by Kerry Irons View Post
    I don't have a fancy clamp like that one, so I just offset mine so that the slot in the clamp doesn't line up with the slot in the seat tube. I can't see any reason wy 180 degrees rotation is functionally any different than a slight rotation of the clamp.
    Symmetry and harmony of the universe are the reasons. Go against this grain and you affect your karma.

  21. #21

  22. #22
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    Oh my, a troll who doesn't know the difference between your and you're. What will they think of next?

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