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Thread: Cooter tests Red and Yellow rear coils.

  1. #1
    EBRforum Expert Cooter's Avatar
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    Cooter tests Red and Yellow rear coils.

    My 2014 (#24) came with the yellow rear coil and I thought it was a bit stiff, so I got a red one and tested them both side to side while they were off the shock. I was surprised by what I found, so I re-tested 2 more times and got repeatable results.



    Last edited by Cooter; 04-27-2018 at 09:53 PM.

  2. #2
    EBRforum Expert Cooter's Avatar
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    Wire diameter .4240(Yellow) vs. .4440 (Red)
    IMG_0724 by Cooter!, on FlickrIMG_0725 by Cooter!, on Flickr

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    EBRforum Expert Cooter's Avatar
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    The free height was 6.4" (yellow) and 7.25" (red)

    IMG_0745 by Cooter!, on Flickr
    IMG_0744 by Cooter!, on Flickr
    Last edited by Cooter; 04-27-2018 at 12:12 PM.

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    EBRforum Expert Cooter's Avatar
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    The yellow weighed 1.85lbs and the red was 2.6lbs:
    IMG_0732 by Cooter!, on Flickr
    IMG_0738 by Cooter!, on Flickr

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    EBRforum Expert Cooter's Avatar
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    At exactly 1" of compression I got 475.5lbs for the red, and 496.5lbs for the yellow
    IMG_0733 by Cooter!, on FlickrIMG_0739 by Cooter!, on Flickrr
    IMG_0741 by Cooter!, on Flickr
    IMG_0739 by Cooter!, on Flickr
    Last edited by Cooter; 04-27-2018 at 12:22 PM.

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    EBRforum Expert Cooter's Avatar
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    I thought there was supposed to be a much bigger spring rate difference than 20lbs?
    I measured sag on the bike with both springs (220lbs rider weight) and couldn't measure a difference at the shock or at the tail.

    Since there is an actual top and bottom to the coils as shown in the EBR tech video, I assume they are progressive, but I'll need to weld a jig together and get a higher capacity scale test the 2nd inch of travel.

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    Very interesting, thank you for your efforts

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    Kool Facts Cooter. Great Job!!!!!!

  9. #9
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    Anyone mind if we revisit this thread for a couple clarifications?

    Quote Originally Posted by Cooter View Post
    I assume they are progressive, but I'll need to weld a jig together and get a higher capacity scale test the 2nd inch of travel.
    Based on the pics, I believe the yellow spring is linear and the red spring is progressive. Even though the wire diameter is about 10% thicker, the SX appears to have 6 full coils vs 5 for the yellow RX spring. The initial spring rate should be lower having an extra coil. But as it compresses, the closely spaced coils come in contact, you get coil bind and it essentially becomes a 5 coil spring. Compressing further, the next coil binds and it effectively becomes a 3 coil spring. A linear rate spring will have even spacing between coils so no coil bind occurs until it's fully compressed.

    I read somewhere the 2014 (yellow) rear spring should be 550lbs/in. The 2015 (red) rear spring is supposed to be 475lbs/in. But if the spring isn't linear that number won't remain a constant.
    Last edited by Brian S; 07-24-2018 at 11:38 PM.

  10. #10
    EBRforum Expert Cooter's Avatar
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    I don't believe there is a difference in RX and SX coils like you say, and the wire diameter is only a 2% difference, not 10%. There is not nearly enough travel on this shock to get into coil bind. Which would be very bad anyway.

    Progressive coils can be made by varying the coils wire diameter, root diameter or winding rate. It happens, but rarely is a coil made to operate with coil binding as a calculation, because coil bind will kill a coil in short order.
    One exception is the "3rd rate coil" on a very long travel coil-over shock. But that can work because they are built to sit at coil-bind and only extend when coils are at free height (shock extension) so all the coils are kept in position on their seats. They are not used to support weight.

    I also read those rate numbers for these coils and thats what drove me to test them. My findings didn't support that rumor but who knows? I do know that a 75lb difference in coil rate would make the sag-height measurably different and that didn't happen either.

    Initially I thought they were slightly progressive simply because they do have a top and bottom direction of install. I now believe that is not the case for two reasons.
    1) There isn't enough travel in this application to make a progessively wound coil to get through its transition period.
    2) The spring rate I found is written as a single rate (same as you did). Not as 225/500lb like a progressive coil would be written.

    I'm still curious, and would still like a MUCH softer spring for me, even at 220lbs. Still tuning compression rates though. We'll see:)

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