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  1. #1
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    Silk Carbon seatpost clamp bolt size?

    Looking to replace with Ti for the weight weenie in me.

  2. #2
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    Quote Originally Posted by Irrenarzt
    Looking to replace with Ti for the weight weenie in me.
    4mm, it is actually a good idea to change the original bolt anyway. The one that came with my silk seatbinder was very short and it ended up stripping.
    However, note that with at least 5.5-6nM of torque you might be pushing the 4mm titanium bolt above its limit. I used a titanium that I had around when the steel stripped but it might be a good idea to stick with steel ... at the end of the story the titanium will save a wapping 2 grams

  3. #3
    TelemarkTumalo
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    I used to think I was a weight weenie. Now, I realize how far I must travel.

    http://forums.mtbr.com/ibis/post-pics-your-ibis-here-195864-4.html#post1907585
    [SIZE="6"][/SIZE]"Dang! You got shocks, pegs. Lucky!

  4. #4
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    Every gram counts some say. Now when they say 4mm, you mean M4 x 20 or 4 mm wrench size? Aaron at Ibis sent me an email stating the bolt was:

    Silk Seat Binder Bolt: 19mm in length, 4mm head.

    In the fastener world, the correct nomenclature is the bolt diameter x thread pitch x length. Typically in the bike world, people don't discuss thread pitch as it is usually a 1 mm pitch or 1.25 if talking M8.

    Since the Silk bolt is a tad bit short (probably by design as too long of a bolt is like that extra piece of TP that stays behind after a serious wipe session, highly unsavory), I figure a 20 mm is correct.

  5. #5
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    M5 x 20+

    Quote Originally Posted by Irrenarzt
    Every gram counts some say. Now when they say 4mm, you mean M4 x 20 or 4 mm wrench size? Aaron at Ibis sent me an email stating the bolt was:

    Silk Seat Binder Bolt: 19mm in length, 4mm head.

    In the fastener world, the correct nomenclature is the bolt diameter x thread pitch x length. Typically in the bike world, people don't discuss thread pitch as it is usually a 1 mm pitch or 1.25 if talking M8.

    Since the Silk bolt is a tad bit short (probably by design as too long of a bolt is like that extra piece of TP that stays behind after a serious wipe session, highly unsavory), I figure a 20 mm is correct.
    I think I need a beeter caliper it is M5 ... sorry. The bolt I am using was a titanium left over from years ago). It was 30mm and I cut it to be flash when torqued down. I would get a 25mm and do the same ... I also take back the worry: 5.5/6 nM for a M5 should be fine.

    I don't know why they use such a small bolt (probably because this is a road seatpost). I made the mistake of adjusting the seatpost on the trail, the steel bolt (partly) stripped and there was no way to put it back ... luckily I was just a couple of miles form home.
    Last edited by Davide; 05-10-2007 at 09:00 AM.

  6. #6
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    Irrenarzt, Why are you already wanting to replace it even when you don't have the clamp yet?? I would suggest to use the standard steel bolt first, so you can easily adjust the height (the seatpost might turn or drop?!) and when you have your final settings, you replace it with a Ti-Version. That way you can measure it yourself and save weight time after time after time. You have to keep savings ahead, otherwise you can't live upto the moment

    @telemarktumalo: this setup took me while to gather.. Main reason is money... Almost all components come from my former bike a Principia alu-bike that cracked....

  7. #7
    mtbr member
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    It just gives me something to do while I wait for my bike to come. The more I have in order when it gets here, the quicker I'll have it set up and ready to go.

  8. #8
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    It's really an M5 x 20 with a 4mm Allan Head

    Hello from Ibis,
    It's really an M5 x 20 with a 4mm Allan Head and a little captured washer.
    If you can find it a 7075 Aluminum one will actually save some weight and will work. We are testing and so far so good... Amazingly it's about the same strength or even a little better than the stainless steel one. If you go the Ti or Al route, try to get a deep socket for the Allan key, like a socket head cap screw instead of a button head.
    Cheers!
    Hans

  9. #9
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    Thanks Hans. I see from pics of the one the binder comes with it has a button style head. I'll look into the options.

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