I currently have a 31.6 seatpost which i want to replace but the one i want is 30.9, can i get a shim to make up such a small amount of slack or would i be better off getting a 27.2 seatpost as there are loads of shims for that sizing?

Shims need to be long and fill the gap properly. What can you not get in a 31.6 that you can in 27.2?

FWIW I only buy droppers in 27.2 or 30.9 and shim up to whatever frame, saves buying a new dropper every frame change, the shim you want is here.

http://www.wiggle.co.uk/ultimate-use-309-internal-shim/

I’ve run a 30.9 reverb in my old BFe using the shim fooman linked to up there, no issues at all.

The USE one’s i’ve used before – tried to use on on my current bike & it was crap.

The perfect thickness cheap, home made shim is a 4pt plastic milk carton IMO. Cut a sleeve, insert with post & it’s great. Doesn’t slip like the USE shims either.

I’ve run a 30.9 reverb in my old BFe using the shim fooman linked to up there, no issues at all.

+1 on my fatty.

How can the USE shim slip, it’s got a lip on it?

Mikewsmith – its a cheap sdg i-beam layback seatpost, very hard to find a 31.6.

Fooman – that looks like it might just work,cheers.

I’m using the wiggle (use) shim on a 30.9 dropper in a 31.6 frame without issue.

i use the USE shim for 30.9->31.6. I bought a reverb in 30.9 specifically for ability to use in either 30.9 or 31.6 with the shim. Works a treat.

As long as the shim goes below the seattube/chainstay/top tube junction you should be ok.

Liteville specify a minimum shim length for their frames.

I also have a USE shim on my 30.9 dropper / 31.6 frame and so far I haven’t ripped anything apart.

I use one of the Wiggle shims too, no issue so far in about 18 months