Seat-Clamp Orientation…….

[sevenfourate]

Slot in clamp lining up with slot in frame ?

Or opposing: to exert more equal force around the clamp / frame ? **Or is that only true / more important on a Carbon post so as to not create a nip point ?

Form, fashion or function 🤷‍♂️

 

[GuyBoden]

Opposing would make sense for stress balance, but not esthetics.

Also, if manufacturers cut the slot in the seat post into the front rather than the rear would less rain get in?

 

[Ajax Bay]

Tightening a seat bolt clamp generates/increases a uniform (tangential) tension in the (circular) clamp so the positioning of the bolt doesn't matter. The tightened clamp exerts uniform centripetal force on the seat tube. The slot is designed to allow tangential movement of the seat tube at the slot which avoids a resisting force. But mainly, it allows the necessary (minimal) reduction in effective diameter of the seat tube: needed for the seat clamp function - to ensure sufficient friction (seat post / seat tube) to stop the post twisting or dropping (under rider's weight).

I can't see that the material the seat post is made of makes a difference, other than affecting the means of ensuring sufficient friction. If the tension is going to be limited (eg 6Nm on the bolt) then the co-efficent of friction (μ) must be increased by using paste (or whatever) - grease on the bolt but not on the post.

Aesthetically and aerodynamically the bolt is best placed at the rear, irrespective of the slot position (which is anyway 'normally' at the back).

 

[rogerzilla]

Opposing would make sense for stress balance, but not esthetics.

Also, if manufacturers cut the slot in the seat post into the front rather than the rear would less rain get in?

Some do!

 

[Jameshow]

I'd put it lined up with the slot so that the friction your applying to the clamp is directly on the post and not trying to tighten the seat tube then the post.... Which then slips because it's not gripped tight enough.

 

[Ajax Bay]

The clamp is not applying friction "directly" to the post. By tightening the clamp it compresses the seat tube: that's exactly what you need to do to "grip" (induce friction of sufficient magnitude) between the tube and the post.

I'd put it lined up with the slot so that the tension you're applying to the clamp is trying to tighten the seat tube onto the post.... which then doesn't slip because it's gripped tight enough.

FTFY

 

[Jameshow]

The clamp is not applying friction "directly" to the post. By tightening the clamp it compresses the seat tube: that's exactly what you need to do to "grip" (induce friction of sufficient magnitude) between the tube and the post.

FTFY

Afaik you have an addition friction between the clamp and tube if the clamp and slot aren't lined up therefore logic dictates that there is less clamping pressure for a given bolt torque?

Where is Brucey when you need him!

A few might know who I'm referring to....

 

[wafter]

My understanding is that in the case of both the clamp and seatpost tube, you're slightly reducing their effective diameter by applying a load / displacement at a single point (the slot) in their circumference.

Hence, any displacement will be greatest at this point and were they not aligned this would require unnecessary slip between components potentially both reducing the clamping force for a given bolt torque and causing un-necessary friction between parts.

As such the slots in both parts should always be aligned.

Here's a pic for anyone offended by slots in the front of the seat tube