Are these ok to use?
Looking to use one to shim my seat post up from 27.2 to 31.6
Both the post and bike frame are carbon and worried my cause problems with flexing etc etc
Shimming a 27.2mm post into a 31.6mm frame is no problem. Often done to add a little more comfort to an overly stiff frame. Done it on my CR1 for long rides - makes a fair difference.
Downside is looks - the post can look a bit think compared to the tubing.
No problem shimming down from 31.6 to 27.2 - some 31.6 posts can be overly-stiff whereas the 27.2 has more give. Shims are made from acetal (USE) and you'll never have to worry about a sticking post either. I've got a 27.2 FSA post into my Battaglin and from a distance you'd never tell - there's more choice in 27.2 posts as well.
Make mine an Italian, with Campagnolo on the side..
Posts
should be fine though
Downside is looks - the post can look a bit think compared to the tubing.