I’m after a seatpost shim for a dropper. 27.2-30. Anyone come across shims longer than 100mm? Looks like that might be a touch in the short side – would barely reach the bottom of the top tube.

Buy several of the USE thermoplastic ones, trim the top ridge from all but one, and glue them together…

Why is 100mm not enough support ? You just need long enough for the seatclamp to grip it, I would have thought.

The glue route is not a bad idea.. I’m probably being over cautious having broken a frame at the seatpost top tube junction – I’d ideally like the shim to extend well down into the seat tube past the top tube. Maybe an engineer will tell me it doesn’t matter and 100mm is plenty to dissipate the load ..

You could use metal ones with one with the metal lip trimmed off – plenty of anti seize on it will probably mean it stays put even without fixing together.

You just need long enough for the seatclamp to grip it, I would have thought.

You need enough shim that the seatpost is internally supporting the top tube/seat tube junction plus a bit to spare. Having the seat post flapping around in the tube but clamped up nice and tight isn’t really a goer.

I got a carbon shim that’s about 150mm long but looking at the site it’s not avauilable in the size the OP wants.

From another thread on here , someone said that it should be 30mm below the bottom of the top tube join

Thanks for responses folks – sounds like a couple of shins might be the way to go – though extracting one from half way down the seat tube might be interesting!