Seatpost shim idea- Mtbr.com
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  1. #1
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    Seatpost shim idea

    Anyone ever thought of doing this (or actually done it) to a shim? Since the seatpost isn't subject to as much latteral forces as it is to forward and backwards forces, I think it could handle it. However, would the lack of surface area compromise the grip on the seatpost and seat tube?

    I'm also wondering if this would work for headseat spacers (anything over 10mm thick)
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  2. #2
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    Quote Originally Posted by BOhNSAI!!!
    Anyone ever thought of doing this (or actually done it) to a shim? Since the seatpost isn't subject to as much latteral forces as it is to forward and backwards forces, I think it could handle it. However, would the lack of surface area compromise the grip on the seatpost and seat tube?

    I'm also wondering if this would work for headseat spacers (anything over 10mm thick)
    sure this works. expect savings between 1-3g

    remember a 10cm long plastic shim weighs ca. 20g so these holes won't do too much...
    cutting the shims to a minimum lenght saves more. i have mine cut to ca. 65-75mm lenght.

  3. #3
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    Good idea. It could even be some webbed structure perhaps, with very little material but good load spread. Those holes as pictured still only save 10-12% I reckon?

  4. #4
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    Quote Originally Posted by nino
    sure this works. expect savings between 1-3g

    remember a 10cm long plastic shim weighs ca. 20g so these holes won't do too much...
    cutting the shims to a minimum lenght saves more. i have mine cut to ca. 65-75mm lenght.
    This was only a quicky draw up to give an idea of what I wanted to do. I'll have to experiment with different hole size, pattern, and number arrays on the computer to come up with a good weight savings-to-surface area ratio. This would be for an aluminum shim by the way. Do they make plastic ones in 27.2 to 30.9 sizes?
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  5. #5
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    this is more what i'm going for (I'm incredibly bored today, can't you tell ) 3D in AutoCAD sucks btw
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  6. #6
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    Since I have nothing better to do today, the calculated weight reductions are:

    cutting the 90mm shim to 75mm results in a 17% weight reduction

    just cutting the holes as in first pic results in a 9% weight reduction (right on Cloxxki )

    and cutting to 75mm and drilling the massive amount of holes as in the second pic results in a whopping 38% weight reduction!
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  7. #7
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    cutting is easier...

    Quote Originally Posted by BOhNSAI!!!
    this is more what i'm going for (I'm incredibly bored today, can't you tell ) 3D in AutoCAD sucks btw
    as i already said above, cut away 20-30mm and the savings are bigger than all those holes combined.

    yes, USE has plastic shims in the size you are looking for. below some shim-weights i measured on my own:

    USE Seatpost Shim (plastic,27.2/30.2x 100mm) : 16g
    Nino's Seatpost shim (34,9/31,6 x 75mm) : 16g
    USE Seatpost Shim (plastic,27.2/31.6x 65mm shortened!) : 18g
    USE Seatpost Shim (plastic,27.2/30.9x 100mm) : 20g
    Extralite Seatpost Shim (plastic, 34.9/ 31,6 x 100mm) : 22g
    USE Seatpost Shim (plastic,27.2/31.6x 100mm) : 27g

  8. #8
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    Quote Originally Posted by BOhNSAI!!!
    Since I have nothing better to do today, the calculated weight reductions are:

    cutting the 90mm shim to 75mm results in a 17% weight reduction

    just cutting the holes as in first pic results in a 9% weight reduction (right on Cloxxki )

    and cutting to 75mm and drilling the massive amount of holes as in the second pic results in a whopping 38% weight reduction!
    how many days did you plan to make all those holes

  9. #9
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    Quote Originally Posted by nino
    how many days did you plan to make all those holes
    I'd let the CNC machine worry about that
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  10. #10
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    I was just thinking about this the other day and it's a good idea. I'd probably start with a plastic shim though which is already much lighter than aluminum.

    I have an aluminum 27.2 - 30.9 that weighs 30 g and it's only 70 mm in length! All that work will just get you down to what a plastic shim already weighs.

  11. #11
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    Quote Originally Posted by nino
    as i already said above, cut away 20-30mm and the savings are bigger than all those holes combined.

    yes, USE has plastic shims in the size you are looking for. below some shim-weights i measured on my own:

    USE Seatpost Shim (plastic,27.2/30.2x 100mm) : 16g
    Nino's Seatpost shim (34,9/31,6 x 75mm) : 16g
    USE Seatpost Shim (plastic,27.2/31.6x 65mm shortened!) : 18g
    USE Seatpost Shim (plastic,27.2/30.9x 100mm) : 20g
    Extralite Seatpost Shim (plastic, 34.9/ 31,6 x 100mm) : 22g
    USE Seatpost Shim (plastic,27.2/31.6x 100mm) : 27g
    ah, i didn't know the USE were plastic I can easily start with one of those
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  12. #12
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    do both !

    You should cut it short and then, drill the holes, saves you time and weight !

    Jean-Sebastien
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