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  1. #1
    Former Bike Wrench
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    Jan 2007
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    15,985

    Idea! Seatstay Pivot Motion

    I wanted to give a visual demonstration to prove a point that I had made in a previous post. I had stated that bikes with seatstay pivots (Faux Bar Links) don't require bearings in that pivot because of the limited movement they experience. In fact, something like a DU bushing (used on rear shocks) are probably the best option. First, here are two pictures of my Jamis XLT...one before compression and one after compression (125mm travel). I have traced a white line over the lines I made on the frame to make the movement more visible.

    At full extension:


    At full compression:


    According to my calipers, the movement was 0.3mm. The pivot is squarish and 23mm top to bottom. If you make that the diameter of a circle, it would give it a circumference of 72.3 mm (rounded to the nearest tenth). So the rotation of the pivot was 0.4% (.004) of the total circumference. Multiply this by 360 degrees and you have a total rotation of 1.44 degrees.

    So why does a bearing designed for full 360 degree rotation need to be there again?

  2. #2
    56-year-old teenager
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    Join Date
    Aug 2006
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    1,763
    That suggests to me that a well-lubricated bushing would work just as well... and might in fact wear better.

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