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  1. #1
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    Polymer bush + Kashima eyelet, free to move too easily or really bad frame alignment?

    Fitted heavy duty shock eyelet hardware, comprising of a polymer bush and steel pin/spacers to my kashima RP23 on my SB66.

    During use, the bush is shifting to one side in the shock eyelet. Checked the fit of the bush in the eyelet, requires a vice to install/remove.

    I assume it is standard practise to design so the bush rotates around the hardware/reducers, whilst the bush stays in a totally fixed position in the eyelet, correct?

    Assuming there is always going to be very minor misalignment between both shock mounting points of the frame, if the eyelet is free enough to rotate on the bush, things are going to shift.

    In comes the new fox low friction hardware -

    Name:  Low-Friction-Bush.jpg
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    Bushes are top hats that can be installed by hand, suggesting a slightly looser fit, i would certainly envisage rotation of the eyelet on the bush, are they top hats to prevent any wandering of the eyelet, side to side on the bush.

    So what im trying to establish really -

    If i want long lasting, low friction hardware, due to maybe the kashima coat and polymer bushes, shock movement side to side isn't constrained, forget the traditional heavy duty kits, i have to go for the fox low friction option?

    Or is my frame just that goosed?

  2. #2
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    Wat?

  3. #3
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    You still need the spacers on each side of the bushing. Your heavy duty steel pins should have still come with the proper width alloy spacers to keep the shock from moving laterally. The black washer-like things in your pic above are those said spacers for a Fox kit. Something similar should have come with the kit you have obtained.

  4. #4
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    What Scott said and it sounds like what you have is either too flimsy (kinda not sure what you have in there) or is the wrong size. It goes without saying that the fit needs to be very snug up in that mess. Nothing should be shifting around.

    mk

  5. #5
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    Hardware is this style-

    Polymer bush + Kashima eyelet, free to move too easily or really bad frame alignment?-35aaaf86-11ec-4121-8e20-9bbb00eac35b_600x450.jpg

    It's not like the rubber seals are going to stop anything shifting. Also, if the spacers were there to keep everything rigidly fixed, they'd eventually contact the sides of the eyelets, causing friction and wear.

    To make it clearer -

    446593d1239306064-advice-needed-rp23-bushing-replacement-bushing_load_fbd.jpg

    What is supposed to happen is figure 20, what i believe to be happening due to lack of friction between the eyelet and bush is figure 21.

  6. #6
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    I can't see but that looks like 6 pieces to me, yeah? I'm not excited about those black things if they are rubber. I'm used to seeing metal from the silver pieces through to the depth of the black suckers in there and that all ending up in the frame, thru-bolted.

    mk

  7. #7
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    Seems like anytime a discussion arises about shock mounting hardware all sorts of acronyms are thrown out and misused. The DU / bushing it fitted (pressed)into the empty eyelet of the shock. A steel pin is inserted (pressed) into the bushing. On the modern 3 piece + designs pin spacers are fitted on either side of the eyelet. Some, as noted above, will have rubber rings as additional pin spacers. The steel pins are sandwiched beteeen the frame / linkage mounts and do not rotate. The shock / bushing rotates around the steel pin. The pin spacers keep the shock centered but should NOT bear any load. OP if the shock is shifting from side to side the steel pins sound too short, they need to be held tightly by frame or suspension mounts.

  8. #8
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    Quote Originally Posted by DeanFBM View Post
    Hardware is this style-

    Click image for larger version. 

Name:	35aaaf86-11ec-4121-8e20-9bbb00eac35b_600x450.jpg 
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    It's not like the rubber seals are going to stop anything shifting. Also, if the spacers were there to keep everything rigidly fixed, they'd eventually contact the sides of the eyelets, causing friction and wear.

    To make it clearer -

    446593d1239306064-advice-needed-rp23-bushing-replacement-bushing_load_fbd.jpg

    What is supposed to happen is figure 20, what i believe to be happening due to lack of friction between the eyelet and bush is figure 21.
    Figure 20 is what is not supposed to happen. The pin that goes through the shock should never rotate, it should be fixed rigidly in the frame. The shock rotates around it.

    The width of shock eyelet+spacers, etc should be just slightly less than the length of the pin. If your pin has signifigant space between the frame and shock spacers, you need wider spacers!

    if you are saying the yellow top hat spacers are rotating in the shock eyelet, I could see this happening. Perhaps that is where Fox is getting the "low friction" from, the eyelet can rotate on the bushings, and the bushings can rotate on the pin. Sounds sloppy and seems like it would wear fast, but that's Fox for ya!

  9. #9
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    in the old DU bushing setup, what rotates against what?

    1) DU bushing vs spacer?
    2) bolt vs spacer

    The friction between bolt and spacer is actually very small.

  10. #10
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    In the old DU bushing the spacers rotate against the bushing.

    In the new 5 piece Fox system the black aluminum pin rotates against the tan bushings.

    In both systems the spacer/pin is fixed to the frame and should NOT rotate. Also, unless something is horribly wrong, the bushing should never rotate inside the shock eyelet.

    On a properly aligned frame there is very little lateral load on the shock eyelets, and the black plastic spacers included with the Fox hardware are more than enough to keep the shock position properly. The tan eyelet bushings have flanges on them to make setting them easier to give the black spacers a nice surface to rotate against. It sounds like your "heavy duty" shock eyelet hardware lacks a means to constrain the lateral movement of the shock.

    The new Fox system is really good, works well, and last a long time. There's little reason to not use it. If you want something even lower friction and you have a fair amount of rotation at the eyelet, take a look at the Enduro roller bearing shock eyelet hardware: ABOUT RWC SHOCK EYE NEEDLE BEARING KITS

    Fox's Kashima coating doesn't have anything to do with the eyelets.

  11. #11
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    Polymer bush + Kashima eyelet, free to move too easily or really bad frame alignment?-img_2452.jpg

    my FOX DHX RC4 comes from a 2011 Trek

    the sleeve doesn't move against the DU bushing. I need a hammer to push that out if I want to swap the spring.

    In my case, the bolt rotates against the sleeve and it's very smooth.

  12. #12
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    I have another bike which uses the old DU bushing. The spacer rotates against the bushing.

  13. #13
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    It looks to me like the bushing is too tight and should be fixed, because you do NOT want the sleeve rotating on the bolt. I'd recommend either upgrading that eyelet to the Fox 5 piece kit or the Enduro roller bearing kit.

  14. #14
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    I believe it's designed like this and wonder the latest session is still using the same design.

    btw, why it's bad to have the bolt rotating inside the sleeve?

  15. #15
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    It's not design to work like that. If the sleeve isn't meant to rotate then they wouldn't even bother putting a bushing in the eyelet. It's bad for the bolt to rotate inside the sleeve because it means the sleeve is also rotating against the frame link, which is going to cause wear on the link. Also when the bolt is tightened down it's pressing the sleeve's ends into the frame link, which is adding a lot of friction.

    It's cheap to fix, so just fix it.

  16. #16
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    What should I change? DU bushing or the sleeve?

  17. #17
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    It's probably the bushing's fault, but considering the new Fox kit costs $13 and the Enduro kit costs about $30, there's no reason not to go with better hardware.

  18. #18
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    the sleeve is very long at 40mm and the bolt (M10) is a special one too. The new Fox low friction bushing doesn't offer this dimension and the enduro kit costs $50 each side. $100 for two bearing is crazy...

    is checking this
    TF Tuned Shox - Mount Kits and Bushings

  19. #19
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    Might be easier and cheaper to just buy polymer bushings and use stock mounting hardware. For example (meant as an example and not as an advertisement): 4 x Performance Polymer Shock Bushings Du Eyelet Bushes Fox RockShox Marzocchi | eBay

    I just bought these bushings but I don't have any experiences yet. I would otherwise invest on needle bearings (at least to the other eylet) but not yet because I will be reshimming rear shock multiple times and I know that needle bearings are a lot harder to clean properly and contaminants will easily damage bearing and sleeve.

  20. #20
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    I do prefer the new Fox low friction bushing as I don't need special tool to replace them

    BTW, thanks mate. I will check that.

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