Coke can shims

tufty

Retro Guru
I've made a plastic seat post shim from a PET "spring water" bottle. Made a lip by putting it in place ad running a heat gun over the exposed part.
 

ultrazenith

Senior Retro Guru
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Has anyone here ever shimmed a frame / seat post to make up a difference of less than 0.2 mm? I've got a bit of a weird case, which I suspect is a frame that was not reamed properly and the main seat tube is 26.8, but the upper 25 cm is about 26.9. When fully tightened, the seat clamp tabs touch each other but the post still slips. A coke can shim that goes abut 25 mm down, and a third of the way around the post circumference seems to have done the trick, but I wonder if it's safe to put a shim around only part of the seat post? Any ideas.
 

jimo746

Gold Trader
MacRetro Rider
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I think unless you get the seat tube reamed properly all the way down, then a make shift shim would be your only option for your particular situation.
 

ultrazenith

Senior Retro Guru
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What frame is it btw.?

It's a Raleigh M Trax Duo Tech from 1995, with the bonded steel and Ti frame. What's a bit odd is these frames (I'm a bit of a collector of them) universally have 27.0 seat posts, and this is the first and only one I have ever heard about with a different diameter. I started to wonder whether it came from the factory incorrectly reamed out, but I'm doubtful Raleigh Special Products would have allowed that to slop through, and in any case the frame has had plenty of use judging by the marks to the finish, so it must have had a correctly fitting seat post at some point in its life.
 

hookooekoo

Retro Guru
Re:

I made a seat-post one for a mate.

Just cut the can to rough size; scissors work well. Then bend as many as fits best around the seat-post to fit in-between it and the seat-tube.

I then bonded (metal-two-part adhesive type stuff) the two 'shim' pieces together and left to set wrapped around the seat-post, wrapped tightly with rubber bands!

You can then anneal the top and 'bend' it over a bit to give a lip so it doesn't drop down.

It works well and still going strong on his bike :)

Not sure of the can thickness, but I could measure for you if required?

Cheers

Pics!...

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That's some great craftsmanship on display! Best DIY shim I've ever seen!
 

grahame

Senior Retro Guru
For a 26.4mm post into a 27.2 diameter seat tube, you will only need 0.4mm of shim, not 0.8mm - the measurements are diameters, and one shim will add thickness on both sides.
 
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