Seatpost slipping down no matter what

[bikeworkshop]

Two pages in and not a single mention of using a Coke can as a shim. This site has gone

Coke can?
You mean
"Euroshopper energy drink"
Retrobikers have "moved on"

@Splatter Paint did mention a drinks can, but has yet to finalise his "product placement" contract...

This, if the seat post wobbles in the frame or drops rapidly down without the clamp present then you can be pretty sure the post is too small for the frame.

Your average aluminium drinks can is 0.1mm thick. So you very carefully cut one up and make a shim 100mm long

 

[rhmcbride]

I have successfully used the drink can shim technique several times.
That said if you can find a professionally made shim with top rolled edge it will ensure a much more secure fit and look much better than a taped on drink can section.
A sheet metal worker or shop could easily make one for you if a manufactured one can't be found.
BTW drink can sections make good bottom bracket sleeves in a pinch or the plastic one gets lost or damaged

 

[Elev12k]

Had the same with my Yo. Changed the Moby for a Heylight post and the Twister for a XTR QR and the issue was solved. Sliding saddles and posts are a common issue for me.

 

[Fatal Swan]

Is it a standard size frame diameter and seatpost diameter (like 34.9 & 31.8 or 31.8 & 27.2)? If so, then surely one of these double layer clamps would do the trick?

This is just one example for illustration, there are different brands/models of the same sort of thing.

 

[winjohn]

I had this issue with my son on his Van Nicholas road bike. He weighs over 120kg so this was always going to be a problem. I solved it by cleaning everything and putting a Hope clamp on it.

 

[Twozaskars]

You could try the twin lever Crank Brothers QR clamp.