For the hassle involved with a coke can, I'd just buy a new seatpost.

Doesn't look like they make that size shim, probably because its such a small difference.

USE make one. I am certain, because I have one. I bought it from Winstanleys.

[url= http://www.winstanleysbikes.co.uk/product/31366/USE_SS_309mm_Seatpost_Shims ]CLICK HERE[/url]

Hiya. I've done this. Best thing you can get us brass sheets 0.035mm ( found in model shops usually by balsa wood etc ) then just wrap it around 0.035 x 2 = 0.07m + 30.9mm = 31.6mm job job.

If you can't find any I got some left over. Yours if you want it.

"probably because its such a small difference"

Not really, thinner shims are available
(25.0-25.4 for eg is almost half as thin)

I've been thinking they should make a 30.9-31.6mm shim for a while so you can buy a 30.9mm adjustable post and use it for 30.9mm or 31.6mm frames. Almost makes 31.6mm adjustable posts not worth buying, in case you buy a 30.9mm frame in future?

"I'd just buy a new seatpost"
A touch pricey if you've an adjustable post though? (or anything else pricey)

I think that's too much space for an ale can shim - they work when you're looking to shim the width of an arse hair. 0.7 mm is quite a bit bigger than that.

As above,you can buy the shim for around 7 quid. They fit in nicely,and they have a nice lip on the top that you can pinch when pulling the post out to keep it in place without it budging. I swap over my dropper post with the other bike quite often and the shim isn't a problem. I would never buy a dropper post in 31.6,it would always be 30.9 to make it more swappable between my bikes. If i had a carbon frame on the other hand.. I would be fitting the correct size post in there.

18bikes have them 🙂 cheers

I brought one from USE last week however do not need it as brought an outer sleeve off here for my Jopin 3 instead.

Email if you want to buy it. Its never been used or even been out the box.