I heard somewhere (I don't remember where) once that a seat post clamp should be oriented with the gap at the front of the seat tube, opposite of the gap in the top of the seat tube. The logic behind this was that it supposedly exerts more equal pressure around the entire seatpost.

However, I've noticed that bikes off the rack are almost always sold the other way around, with the two gaps on top of each other.

Does it really matter? Is one way better than the other?

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    Don't know that it matters much. Some bikes come with an integral clamp and it necessarily "faces backwards", since there's only one "gap". "Loose" clamps are usually oriented the same way, but probably as much for looks as anything. – Daniel R Hicks Sep 26 '13 at 3:25
  • My current mountain frame has a pair of cut outs, what to do there, sideways? I prefer to have the clamp facing forwards as it keeps the threads a little cleaner. – alex Sep 26 '13 at 5:32
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    My mechanical intuition says you want the gaps lined up, but my common sense says unless you've got a $10K bike and you're competing professionally at world-class levels, it probably doesn't make one damn bit of difference. – Carey Gregory Sep 26 '13 at 5:38
  • My seat-post and seat-tube have symmetric wing profiles. The seat-post has a rear-facing slot while the clamp is slotted at the front. – Carel May 17 at 19:31

Typically, for an aluminum post you align the gaps. For a carbon post you turn the clamp 180 degrees from the gap in the seattube to minimize the chance of crimping the seatpost. Some manufacturers have their own recommendations, but they're typically in line with what the aforementioned guidelines.

  • This makes sense. Just for the sake of completeness: what about steel or titanium? – jimchristie Sep 30 '13 at 21:46

Aligning the gaps will allow the clamp to compress the tube a little better, therefore reducing the amount of tension needed from the clamp to hold the seat post in. And less tension means a longer life for your seat post clamp.

Now, there's the issue of which way your clamp lever faces if you use a quick release clamp. Most have it facing backwards so it doesn't interfere with clothing and doesn't catch on anything while riding. But, with something this small and utilitarian, I think you can put it any way that keeps your seat post from falling and it's probably OK.


According to a forumer working in bike building industry (SUNN, France), mounting the seat post clamp with its gap on top of the seat tube gap is important to ensure an equal and secure gripping.

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    +1 In my experience, some clamps don't grip properly unless the gaps are lined up. The same is true of shims inside the seat tube. – James Bradbury Sep 26 '13 at 7:45

My two cents:

If you align the gap in the tube with the gap in the clamp, the grip will be much stronger. You'll need less force in the lever to hold the seatpost in place.

If you keep them counter-aligned, you'll exert considerably less pressure, and there is a chance that the pressure will be "more evenly" distributed, although I don't "feel" it to be necessarily like this, since it is only the frame itself that actually deforms to grip the seatpost, and I think it tends do deform the same way on both cases (a lot of common-sense here, that would need experimental data to be totally sure).

My advice would be: use first option UNLESS you have reasons not to do so. Such reasons could be: sensitive seatpost (carbon fiber, delicate metals), or a tendency from the clamp to leave marks/grooves in the seatpost.


It is not the clamp who bite into the post. The edges of the seat tube will. If you align the slit of the tube with the slit of the clamp the tendency of the edges will be to follow the easy resistance path which is a straight line and not a curved line. If the clamp is reversed, using a relative thick non deformable clamp, the edges of the tube will follow the radius and not crimp into the post. Of course the effort of tightening will be substantial cause now the clamp act to the whole section of the tube and not just to the edges

  • Interesting, so which is better? Can you edit in an explanation of which is better or whether it matter? – Swifty May 15 at 7:54
  • In my thinking better meant the easiest tightening force so basically aligning the slit of the post with the slit of the clamp is the correct engineering way. But this suppose a tight adjust with tight tollerance to be effective. Reversing the clamp give the chance to compensate the precision of the adjustment because the clamp will deform the tube more uniform. The problem here is if the deformation of the tube you want to allow is supported by the resistance of material because you have to apply a lot of force in reversed mode. Is all of compromise. – CatG May 15 at 21:30

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