Carbon seatpost and shim

woodchips69

Is it ok to use a carbon seatpost with an aluminium shim?

I want to use a 27.2mm Specialized zertz carbon seatpost in a 31.6 seat-tube to add a bit more comfort.

brin

when i bought my new bike last year i told shop i was going to use my own spesh seat post (the same as yours), the mechanic told me the seat tube was a bigger diameter so i suggested inserting a shim, but he advised against it as he reckoned they weren't a good alternative,and they have been known to create an annoying rattle with it vibrating. this in no way affected the price of my bike, so seemed there was some truth in his advice, i have seen threads on other forums where people have used shims with no problems, so seems the truth of the pudding....? They are quite cheap, so you could try one first and if not happy change the post.

ride_whenever

Load of bollocks...

I'd use a USE thermoplastic shim with carbon assembly paste both sides (assuming carbon frame as well, grease on outside if ally frame) Mine didn't rattle at all, which i'm also selling if you're interested

Berk Bonebonce

woodchips69 wrote:

Is it ok to use a carbon seatpost with an aluminium shim?

Of course.

However, I would advise on buying two or three in order to get a good fit. Or even take your bike along. The real problem is with steel frames where a poor fitting shim has the potential to result in damage to the brazed-on seat clamp fixings.

The comfort gains from a carbon seatpin are likely to be barely perceptible. Fatter tyres and a saddle with more padding get results in respect of comfort.

woodchips69

Sorry, but I probably should have said what bike it's for. I want to use it on my Ribble Carbon Sportive road bike.
I already use a shim on my Giant full susser (aluminium to aluminium) and have had no problems at all with it, but was wondering if a carbon post with a shim would be ok in a carbon road frame.

murraymint77

I could be wrong but i think ribble say not to use a shim on there carbon frames.
Seem to remember them saying this when i got my Gran fondo.

Monty Dog

Been using USE shims on carbon frames for yonks without any problems - however, I'd steer clear of aluminium shims purely from a galvanic corrosion perspective, unless you're rigorous with maintenance i.e. remove and relube regularly. As for seat shims rattling - WTF?