I’ve just bought a USE Thermoplastic seatpost shim for using a gravity dropper (27.2mm) on an SX Trail (30.9mm seat-tube internal diameter). I’m using a Hope QR seatpost clamp as I will still want to drop the post as low as it will go on occasion. I have done it up pretty tight but the post slips down very easily and from side to side.
Has anyone else had this problem and if so, how did you fix it?
Thanks

I expect your seat clamp is a bit dirty – there might be some mud or grit between the cam and the brass bushing. If this happens it can feel like you’re clamping it up tightly but you’re not. Give it a clean and grease and it should sort it.

By coincidence, I have a USE shim on my desk this morning. Box says you must not grease between the shim and the post. Have you?

i find the thermoplastic shims undersized. currently using one 0.2mm bigger than i should need and it all fits together perfect, no slipping.

I used the same shim for a GD on my turner (30.9 also) and found it to be loose. Measuring the shim diameter whilst on the post and it came out about 30.7mm so I ended up getting a 31.0mm alloy one from the CRC flood sale which is a perfect fit.

They still have em too!

CRC

arraldite..?!

If you get no joy, get a metal shim instead. Chainreaction used to do them, think they still do. edit – just noticed the above link!

thanks everyone. It does appear to be slightly smaller than stated so i have now ordered a metal one by a different manufacturer.
Cheers

Maybe try lightly roughing up the shim with a pit of wet + dry.
Hairspray sometimes works as well – just gives it that bit of ‘tack’.

use carbon assembly paste.. its almost a toothpaste type substance with suspended particles in it.. at least thats what the Scott carbon paste is like. Presumably it helps it grab?