I've just got myself a Carbon 456 Evo frame and was wondering if I'm ok to run a 27.2mm dropper with a shim in the frame. If it makes any difference I'm a slightly lardy 15 1/2 stone.
I run one in my Cube carbon frame for my Reverb, and for a while I ran two (had a 27.2 dropper and it's a 34.9).
But I 'only' weigh 12 stone 🙂
Never had any trouble with one in my Carbine. 13 stone and used it as intended.
Don't do it! The frame will explode and then you'll have a massive thread here about how On-One are the Devil for not warrantying your frame.
Actually that probably won't happen but there have been a good number of threads about seattube failures and manufacturers not replacing the frame as a shim was used. Varies by manufacturer though and the 456 is pretty over built and not *that* expensive to replace if the worst really did happen. Just get on with it 😀
Depending on the shim material, if it's an aluminium shim, I'd be very careful, lots of grease/assembly paste to stop it corroding into the frame. If it's plastic then it should be fine.
Been running a shim in my road bike for years - it came with it. Only problem was once the anodising wore off (it's an alloy shim) I had some bad corrosion.
Try and get a non-corroding shim or check/clean/repaint/replace it if not.
Install post with carbon assembly paste to prevent electrolytic corrosion and it should be fine.
Every month or so just take it out and check it and reapply if necessary.
I wouldn't use grease as it can affect the resin in the carbon fibre.