Seat tube shim adapters are quite expensive, what kind of material do you recommend as a shim?

I have seen in a thread some guys talking about home made shim:

  • paper tape
  • alloy drink can as a shim (aluminium or steel?)
  • Thin and quality paper/cardboard

Which one would be the best?

  • 3
    I would go with the pop/beer can. Among other things, the thickness of the metal varies with the height along the side of the can, so you can customize the thickness. And paper/cardboard will compress too easily and make a lousy shim. Mar 26, 2015 at 11:07
  • @DanielRHicks Would you choose steel or aluminium can? Some says that aluminium won't slide that easily, but have no idea why.
    – JinSnow
    Mar 26, 2015 at 11:11
  • 2
    Aluminum is easier to work with and "conforms", making it a better shim in most case. Steel will take wear a bit better in cases where the fit is poor. Aluminum will "stick" to steel in a way, which is probably good, to keep it from sliding around when you want it to stay put. Mar 26, 2015 at 11:16
  • 4
    When you get the shim in place, make sure there's at least 1/4" or so showing above the top of the tube, then use a thin screwdriver to bend the top of the shim outward, to make a "lip" that will help keep it from falling into the tube. Mar 26, 2015 at 11:17
  • 1
    Why shim, if you can buy the right sized seat post?
    – Criggie
    Sep 28, 2017 at 0:24

4 Answers 4


Soda cans do the trick, cf this tuto

enter image description here

  • 3
    That looks like a recipe for a death by a thousand cuts!
    – andy256
    Apr 21, 2015 at 9:22
  • 2
    @andy256 - Well, one presumes that he'd put a seat on top of it. But there's no need for the "ears" to be that long -- 1/4 inch is plenty. Apr 21, 2015 at 11:44
  • 1
    @DanielRHicks, You're right, this was an artistic touch! Quite nice, hey!
    – MagTun
    Apr 21, 2015 at 12:24
  • 1
    This is generally the right answer (I think), but I would not use an aluminum shim on a carbon-fiber frame and/or with a carbon-fiber seatpost, because galvanic corrosion can occur between CF and Al.
    – Adam Rice
    Sep 27, 2017 at 22:18
  • 1
    No, CF and aluminum. It’s a well-known problem.
    – Adam Rice
    Sep 28, 2017 at 1:59

Definitely alloy drink can or other thin sheet metal as it is not compressible and is not affected by water, oil or grease.


Try a rubber sheet cut to size and rolled around the seatpost. It won't slip. Just an idea.

  • 2
    If you have that much slop, you have the wrong-sized seat post.
    – Criggie
    Jul 11, 2016 at 19:55
  • 1
    Welcome to Bicycles @Sally. Good to see you here. Since each site is different, I recommend that you take our tour and read through the help center. Then you'll understand why I say this should have been a comment. But I think it would be hard to the rubber in position, and the seat would still feel a bit loose. Hope to see another post from you
    – andy256
    Jul 11, 2016 at 23:11

Done this a few times, including on trailer DIY axle and the standard pop alum held up over a couple years there without issue. Also on a prior seatpost issue.

  • TO THE GUYS WHO SAY BUY THE RIGHT SIZE SEATPOST there are manufacturers (AND OTHER APPLICATIONS) who don't think standards are for them.
    Example - just bought a folding e-bike with 36mm seat post. It's also literally twice as long. It spans use from 5'2" TO 6'5" (157-196 cm) (FUNNY!) and (it says) is good to support 395 pounds (180 kg). Well - there you go. Now I want a suspender to go with my hard-tail - and the biggest they have is 31.6. Which means folding or layering that can - which I did before.

However I would also be willing to try thin sheet aluminium/aluminum from the hardware store - and some kinds of plastic sheet used for durability (thick heat pressed packaging keeps it's properties under extremes.)

I also discovered a handy source of stainless in just about that thickness (2mm/79 thou) - hidden inside just about any hanging file folder. I went to throw out a bunch and said - hey -- these would be like 40 US cents apiece. And not only that, but I THINK the folder material would be good for most stenciling apps since it's a hard all through and somewhat water resistant. Where else do you find 20x15 sheets of stencil blanks for free?

So yeah - I think you just cut a bunch and drop them in to make a circle - if it fits. Bend, solder, cut, done!

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