Is it a bad idea to use a shim for my seatpost?

by sponging-machine   March 27, 2009  

I'm keen to change my aluminium post for a carbon one but I'm struggling to find one I like/can afford in 30.9.

I've seen plenty in 27.2 and have a reducer shim from my mtb. Would this be a daft idea with a carbon post, especially considering I'm 115kg?

3 user comments

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I would shy away from this practice. Most budget "Carbon" models are pretty hardy in my experience but given your size and weight it would be very, very painful were one to fail and you'd void the warrantee into the bargain.

Shaun Audane's picture

posted by Shaun Audane [779 posts]
28th March 2009 - 0:17


as a fairly heavy rider too, who's broken more than one frame at the seat tube/top junction i'd tend to agree with shaun. by adding the shim you're decreasing the area over which the forces are dissipated through that critical junction (unless you can find a really long shim). so it's more likely to break.

you can get cheap carbon posts in 30.9 though... this one
is only 30 quid and you can get decent FSA and Kore ones for around 50 notes

purplecup's picture

posted by purplecup [233 posts]
28th March 2009 - 9:37


Thanks chaps. That was my train of thought, and why I'd never dream of doing it with my MTB. Having searched around, I've also found a few posts (including the FSA) for around £50 in a 30.9, so all good.

I just need to find a matching stem and bars, 'cos I'm a tart!

sponging-machine's picture

posted by sponging-machine [109 posts]
30th March 2009 - 7:58

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