Viewing 11 posts - 1 through 11 (of 11 total)
  • Talk to me about shims
  • Coyote
    Free Member

    I’m about to swap frames and my current one has a 27.2 seatpost whereas the new one needs a 30.9. As it’s a Thompson I don’t want to sell mine and then have to buy another one. Has anyone used a shim for this? What were your experiences? Is there a particular one you’d go for or avoid?

    Cheers.

    clubber
    Free Member

    Shims are much of a muchness (though USE ones being plastic are light and are almost always creak free) but the important thing is to ensure that the shim is long enough to sit far enough in the frame (ie the same as if it was a normal seatpost) or you risk damaging your frame – this can be an issue with some frames that have a very long extended seat tube or a seat mast type arrangement (eg Pace 305)

    Oh and shims will also allow water into the frame if you ride in really wet conditions so remember to empty the water out from time to time (or pack it with grease or even silicone sealant).

    Chase
    Free Member

    Amazing. I was just about to post the exact same thing. 27.2 up to 30.9 on my new frame.
    The new frame states a minimum 4″ seatpost insertion so I will need a shim 4″ long. Wiggle are the only place I have found the size I need so far.
    Are shims just a short term fix or a long term possibility?

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    stevomcd
    Free Member

    Sell your post and buy a new one (always a ready market for Thomson posts on here).

    If you move your saddle up and down at all, you will HATE the shim very quickly.

    cynic-al
    Free Member

    what my soon-to-be Alps buddy Stevo said.

    shims are CRAP end you will not spend much in selling & replacing your hallowed Thomsom seatpost.

    Seriously, buy the right thing, shims are RUBBISH unless you never touch the seatpost, not to mention insertion issues.

    jackthedog
    Free Member

    I run a shimmed seatpost and have done for 5 years. I adjust the saddle very frequently whilst riding. It’s not the end of the world, and you get the bonus that all the crap and grit that gets sprayed all over your seatpost doesn’t get rammed into the frame when you lower the saddle, scoring it half to death.

    I only have it because the bike came with it. I wouldn’t choose to run a shim over running a proper size post, but I certainly wouldn’t go out of my way to get rid of a shim. A tiny bit of extra attention when adjusting the saddle is a good pay off for saving a few quid.

    But then I am a Yorkshireman, so I might just be a bit tight…

    mk1fan
    Free Member

    I have a shim for my Descender post. Although this set up means I don’t need to move the post up and down.

    james
    Free Member

    “Sell your post and buy a new one”

    You have a 27.2 Thomson seatpost, which is narrow enough to flex a bit. If you go upto a 30.9mm it’ll not flex a lot, being so wide and stiff. Thomsons aren’t exaclty known for being forgiving. For some reason I’m assuming its going into a hardtail frame (if not ignore me), then it might be worth shimming it and keeping a narrow post for comforts sake

    I’ve a USE shim on a bontrager carbon post and it slips down without a problem, and to pull up just touch the shim [its not tight on the post/in the frame, despite being the right size so doesn’t get stuck) to stop it pulling up as I pull the seatpost back upto pedalling hieght. No problems with one here

    mattsccm
    Free Member

    I was thinking of exactly the same thing , sizes as well! My 30.9 is buggered, doesn’t stay tight at the top and I have several very good 27.2’s. Also very skint so a shim makes sense to me

    takisawa2
    Full Member

    27.2 is a common size so it’ll sell on here.
    Likewise 30.9 is also common so you shouldn’t have much trouble picking one up. They generally go for about £35 or so.
    Shims are fine, I ran them for a long time but they can slip sometimes.
    If it were me I’d sell the 27.2 & buy a 30.9.

    Oh, & 27.2 Thomsons do flex, trust me…!!!

    Coyote
    Free Member

    Hmmm… thinking that selling the 27.2 may be the way forward. It’s prettu much mint so the differential between that and a replacement 30.9 shouldn’t be too horrendous.

    Thanks for all the input, much appreciated.

Viewing 11 posts - 1 through 11 (of 11 total)

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