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.

 

[Tootyred]

Im with @bikeworkshop on this one. Either try wobbling it or even better, buy a cheap set of bore gauges...my set at home for measuring unimportant stuff was £6 ! That way you can measure the seat tube 3 or 4 " down inside....not round the often crimped camp area. A good investment for anybody as it removes the "post trial and error" phase of a build.

If the post is right you shouldn't reslly need a "fix around", provided the clamp doesn't have a design flaw, such as a big old bit of plastic in it or a weeedy external cam.

 

[PanoIgano]

Thanks for the ideas guys!

So far, what I have managed to do and seems to be working is to simply replace the QR with an allen screw. This keeps the seatpost in place.

Nevertheless, quite a few ideas in this thread of what to do in cases where nothing seems to work. I quite liked the idea of adding a CatEye light clamp. Tried this in the past and worked wonders.

 

[1552]

Are you 100% sure the seat post is the correct size?
It looks to be a Fat Chance yo eddy?
These use a specific size post, quite hard to find, 29.4 from memory.

 

[Imlach]

Have it welded in place