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Externally fastened bearings?

Discussion in 'Downhill & Freeride' started by Vrock, Dec 16, 2005.

  1. Vrock

    Vrock Linkage Design Blog

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    I have a question about bearings, pivots and stiffness...

    I've seen that some bikes clamp the bearings to the Swingarms and others suspension members, and they use to be the bikes that people say that are very stiff. Others bikes simply press fit the bearings.

    What are the differences??? Witch system is better/stiffer???
     

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  2. Fulton

    Fulton Monkey

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    provided you don't have to remove the part(bearing) very often, a press fit is usually lighter, simplier, and more reliable
     
  3. beaverbiker

    beaverbiker Monkey

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    While I do agree with what Fulton said, a pinch bolt system allows for easy maintenance and may also allow the bearing to last longer. You can vary the amount of preload on the bearing by how much force is in the pinch bolt. Having the right amount of preload on a bearing will help it last a lot longer without it binding up or developing "slop". With a press-fit system, you get whatever clearance you end up with after the tolerances on the o.d. and i.d. of the bearing, wall thicknesses of the races, ball bearing size, and the hole in the frame. Usually it's not too bad because you can specify how much clearance you want in the bearing itself, allowing for the outer race to distort more without causing the bearing to bind up. However, the larger the clearance, the more "slop" may develop in your bearings.

    Hope that helps.

    -beavers
     
  4. buildyourown

    buildyourown Turbo Monkey

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    From a manufacturing stand point, it's way easier to make a pinch bolt than a press fit.
    Your hole size has to be about 10x more accurate when making the press fit.


    IMO, the best systems use tapers. ie, the main pivot on a DHR. This introduces some other issues which is why bearings on a DHR have to be installed with special loc-tite.
     
  5. beaverbiker

    beaverbiker Monkey

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    most press fits use a cylindrical surface loc-tite. it allows for the plus side tolerances on the hole to be a little larger.
     
  6. Vrock

    Vrock Linkage Design Blog

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    Thank you very much for your answers. One friend of mine is starting a brand and I'm designing a bike for him. Its a Burly Faux-bar with the shock mounted to the top tube and 160mm of travel. I'm pretty sure that the main pivot and rocker fix pivot are going to have pinch bolt system. I'm not sure about the other two pivots, but time will tell. I'll investigate that pivot in the DHR too.

    Here are a couple of pics of the main pivot...
     

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