Slightly peculiar seatpost shim

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  • Slightly peculiar seatpost shim
  • andrewh

    I have a 27.2 seat post and a 30.0 seat tube (seemed the only way of getting a dropper into a 30.0)
    I bought a shim, but it seems quite odd. The internal diameter is fine but it appears to be sort of tapered outside. This means that it doesn’t push down all the way into the frame and presumably there is very little contact between seatpost, shim and seat tube and so the seatpost revolves in a rather annoying manner. I have changed from a QR to a bolted collar but this hasn’t helped.
    Is it normal for shims to be tapered like that?
    Would buying a nice straight one solve my seat rotation issues? Any recommendations as to which one to go for?
    Not quite sure what the current one is, but it’s made up of two parts, one inside the other, and is silver. It was fine in my old frame, which was also 30.0


    Anyone got any ideas?


    I’ve got a USE one that’s rock solid. What brand is yours?


    I have seen quite a few that taper and have 2 seperate shims. I think this is more what you are after shim


    Good old tapering frame snapper shims, i suggest you stop using that shim.

    Use make the only shims id consider


    ….Or go for a 30.0 dropper?

    Gravity Dropper amongst others make 5 inch droppers in 30.0 seatpost size. Meaning you won’t need a shim at all.

    Premier Icon Onzadog

    Depending on the frame, it might be possible to ream it out to 30.9

    Premier Icon letmetalktomark

    The shim should go all the way into the frame … Definitely not half way in.

    Pace offer a 30.0 to 27.2 shim as their 26″ steel frame uses a 30.0 post.

    iIRC it was longer than the USE one at 125mm but cannot be sure as managed to find a 30.0 post before needing a shim.

    There was a Kona in the classifieds a week or so ago that had had its ST reamed from 30.0 to 30.9 by 18Bikes.

    May be helpful and 27.2 droppers re sell well.

    There certainly wasn’t the metal on my Pace for this though 🙁


    Dan and Trail rat, thanks, it’s not just me dim then, it really is a silly design!
    I do actually have a Kona (a 2008 Stinky) and asked on here a little while about having it reamed out to 30.9 so I could get a Reverb I it but this suggestion didn’t meet with much approval!
    I’ll try the USE shim first, see how I get on with that, consensus above seems to be that they are the ones to go for. If it doesn’t work I’ll look at reaming again. Not sure about a GD, if I was going to buy another I’d want a proper hydraulic one I think..

    Thanks all.

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