i've searched past posts on this question, and did not find an acceptable answer (mostly static from "gee-whiz" guessers...):

problem:
alien carbon 27.2mm dia post
stock giant tcr comp. seat collar clamp - the one with the diagonal cut in the back
seat clamp size 31.8mm
tube and post are clean and spotless

seatpost contantly slips under normal riding conditions. extremely annoying.

bolt tension is tight, so much that i hesitate to crank further from fear of stripping the bolt or damaging carbon frame "lug". it's as tight as you can comfortably hold an allen key during torqueing.

i've tried a better quality seat clamp collar, salsa lip lock, but to no avail. post held slightly better, but eventually slipped albeit at a slower rate.

the posts about hairspray and jelly/preserves sound far fetched, besides they are both water soluble and therefore temporary solutions.

shim idea sounds interesting, but what thickness? and material?
a shim could quite possibly make impressions into the seatpost wall, not a good thing, but sounds like the most promising.

carbon post surface indeed seems slippery, and so does the inside of the carbon frame. this seems like the root cause of the problem. it does not help that the seat frame "lug" is slightly tapered on the O.D., which decreases clamping surface/pressure (poor design, even trek has better shaping in this area).

if carbon to carbon interface is too slippery i may try a different material post. alum or ti.

has anyone else had similar experiences? what were your solutions?

i've searched past posts on this question, and did not find an acceptable answer (mostly static from "gee-whiz" guessers...):

problem:
alien carbon 27.2mm dia post
stock giant tcr comp. seat collar clamp - the one with the diagonal cut in the back
seat clamp size 31.8mm
tube and post are clean and spotless

seatpost contantly slips under normal riding conditions. extremely annoying.

has anyone else had similar experiences? what were your solutions?

I had the same problem with my 2004 TCR frame. I roughed up the surface of the clear coat with some 220 grit sandpaper below the portion that showed. Problem solved. It's been 8 months and no problem. It can be polished back if needed.

I had the same problem with my 2004 TCR frame. I roughed up the surface of the clear coat with some 220 grit sandpaper below the portion that showed. Problem solved. It's been 8 months and no problem. It can be polished back if needed.

tried the 220 grit on the portion beneath the seatclamp. test rode by jumping some curbs while seated (ouch, not something i would recommend doing regularly). seatpost stayed put (marked with some tape).

it broke the shiny clear coat glaze on the carbon, but this seems to give the clamp just enough "bite" to hold the post properly. this idea would work on any seatpost, only drawback is if you change frames/bikes. the dull matte finish produced may not be as sexy, but bottom line it works.

looks good, long distance testing to follow...

thanks for the tip.

I sand down the clearcoat on all my carbon posts and then apply hairspray. This always works for me.

this idea would work on any seatpost, only drawback is if you change frames/bikes. the dull matte finish produced may not be as sexy, but bottom line it works.

thanks for the tip.

Glad to help. The clear can easily be brought back to shiny with a little work. Sanding with 400 then 600 and 2 grits (medium and fine)of rubbing compound will make it just like new again(but I doubt anyone will ultimately want that again if they actually use the post.

yah... hair spray may sound far fetched and because you think it is water soluable it is temproary solution - but it works..

Sometimes the simplest solution is the best one... hairspray the post once and you'll not have slipping problems. How often do you take it out and wash the post anyway....