Giant Cadex problem

[Skapegoat]

I have a Giant Cadex Aluminium frame I built up as a hybrid.
All is working well apart from the seatpost.
I have tightened the bolt as much as I feel it should and yet the seatpost keeps slipping down when riding.
It's the correct size for the seat tube.


Any gentle ideas to solve this?
Grip paste?
Take the seatpost out and tightened the bolt to get a better grip?
New seatbolt?
Shim?

Any ideas or experience welcome?
Thanks.

 

[moonlite]

The time-honoured beer can shim might be worth a try. Easy to cut to size, low-cost, no damage to frame or post.

https://www.velonews.com/gear/making-it-work-have-a-beer-fix-your-bike/

 

[Skapegoat]

The time-honoured beer can shim might be worth a try. Easy to cut to size, low-cost, no damage to frame or post.

https://www.velonews.com/gear/making-it-work-have-a-beer-fix-your-bike/

Brilliant, I'm going to buy some beer so!

 

[MuchAlohaNui]

A wild concept, subjective yes, but maybe use the right diameter seatpost? I understand you are using the 'right' size, but is incorrect. Your current size may be off by half a mm or more.

Catalog specs have been known to be wrong.

 

[Mod-Master]

Look at the bottom of the seatpost and find the size, it usually says it there. Then get some verniers or a ruler and measure the seattube. If it’s not the same size then there you go.

If it is then I don’t know what your problem is

 

[rikster]

It's a 27.2mm seat post on my Giant Cadex and not had a problem with it slipping.

 

[hamster]

As a final point, just becasue it says 27.2 on the post doesn't mean it's 27.2. I've had ones closer to 27.0!