Best material for a shim for seat post?

[Brucey]

A single layer i probably best, but I think a double layer will be fine.

[Maharg]

I had the same problem fitting a UK made seatpost on to a US touring frame (Surly Long Haul Trucker). It was, in other words, a conflict between imperial and metric measurements. Add a Pitlock security clamp into the situation and things got even more complicated. Fortunately a thin strip of copper shim (purchased from B&Q) solved the problem completely.

[Keezx]

.......Diameter of the titanium sleeve was spot-on , but the inner surface was too smooth........

how did you measure it? I have never seen a moving seatpost that did not also wobble, and Ti would be the last material I'd expect problems with.

That sleeve was slotted over the entire length (80 mm) so measurement is not relevant.
The post did slide in with some effort though, so to my assessment it had the right dimensions.

[Brucey]

ah, I see; I think you need to carefully measure the assembled diameter of the seat pin + shim and compare, to see if it possible for the bottom of the seat pin to move inside the seat tube, or not.
If it is as I suspect all it would have taken to effect a complete cure would have been a few turns of tape around the base of the shim.

[Keezx]

My guess is that on a microscopic level , aluminium oxide has more grip on a soft surface (Carbon seat post) than titanium oxide.
As in : braking with aluminium rims works better than steel&chrome rims.

[Brucey]

My guess is that on a microscopic level , aluminium oxide has more grip on a soft surface (Carbon seat post) than titanium oxide.
As in : braking with aluminium rims works better than steel&chrome rims.

it probanly does. But the usual problem when Ti is involved is galling causing things to become stuck, not loose. So I still think your Ti shim might have been undersized on wall thickness, and allowed the seat pin bottom to move around slightly. On my own Ti bikes, I always used Ti posts too, and there is no such thing as 'too smooth to grip' in my book.