Originally Posted by
ljsense
I'd guess it's a 27.2 carbon post epoxied into a 31.8 or 31.6.
The epoxy is not an issue -- it's stronger than the binding force you'd get from tightening a seatpost collar.
The problems may be the length of the carbon post. And whether it was sanded down to fit.
If you can measure the inserted post and it's still 27.2 and it goes a long way -- like 5 or 6 cm -- into the alloy sleeve, the only issues will be aesthetic.
You should just be able to feel how deep it goes by running a spoke or something similar up the bottom.
It doesn't look like carbon to me. I would highly doubt that it is on an older C'dale anyway.
I tried using a 27.2->30 shim with a carbon post and a carbon frame and could never get it to hold. And yes, I used carbon paste too. I gave up and found an original post for the bike, the same as my own original, except mine stripped the ridges that held the saddle angle. It isn't a great design, nor is 30.0 a great diameter. Only Thompson makes an alloy one but I couldn't find a CF post anywhere in that size except an original.