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Finally doing the Shiver bushing enhancement...

Discussion in 'Downhill & Freeride' started by zedro, Oct 4, 2005.

  1. zedro

    zedro Turbo Monkey

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    finally after over a month of backorder waiting my bushings came in and my little experiment can begin. The plan is to add a third bushing in the middle of the two original bushing locations by removing a 15mm section in the spacer shown below. WB supposidly uses this arrangement and since people have said how it feels stiffer (despite a smaller structure) I'd figure I'd give it a try next overhaul. So after turning 5 years old this year and getting pretty shaky, it was finally time (and overdue) to change the bushes and seals. The process was really painless, the bushings came out by hand and by tapping on a socket and extention, the spacer was cut via Dremel cutting wheel using tape as a guide and sand paper for cleanup, popped it all back in and presto, a really really stictionny fork.

    I'm hoping theres a noticible difference; the FEA simulation i did last year when i proposed this suggested a possible 25% decrease in deflection (one leg, perpendicular force to the axle when fully extended). Wont be doing the lab study i was going to do :rolleyes:
     

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    #1 -   Oct 4, 2005

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  2. zedro

    zedro Turbo Monkey

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    heres the simulation i dug up from last year, one is the FEA with the displacement 'thermometer' showing the increased stiffness, the other pic shows why having more points of contact would increase stiffness (top shows tube-in-tube with two points of contact, the lower one with 4)
     

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    #2 -   Oct 4, 2005
  3. jackalope

    jackalope Mental acuity - 1%

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    Huh...Pretty nifty scheme there Zed... :thumb:
    So after the mod, the fork feels sticky again (i.e. like an out of the box fork)? Any lengthened break-in period I wonder?

    Also, were you the one who made one leg into air spring via a ghetto rigged schraeder valve set up? :think:
     
    #3 -   Oct 4, 2005
  4. kidwoo

    kidwoo Celebrating No-Pants Day

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    Still looks flexy.

    If that's all that wb is doing now that's different, then this should work well. Curb huckers fork was way stiffer than the stock wb forks I owned.
     
    #4 -   Oct 4, 2005
  5. zedro

    zedro Turbo Monkey

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    yeah i did that mod. The seals are new and the bushings seem to come with a powdered coating on them, maybe for anti-corrosion, so hopefully it'll loosen up pretty quick. Guess it'll just feel like a Dorado for now :D
     
    #5 -   Oct 4, 2005
  6. zedro

    zedro Turbo Monkey

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    yeah someone noted that while the WB was stiffer, it lacked the smoothness, so maybe theres the tradeoff. Shivers seem to have come with looser tolerances, these 888 bushings may be tighter too i dunno
     
    #6 -   Oct 4, 2005
  7. vitox

    vitox Turbo Monkey

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    from what i can recall, no matter how the bushings were arranged on the dh3/dh2.0`s, the fork felt stiffer than a shiver. hope you find out its otherwise but i think in this case its another factor thats contributing.
     
    #7 -   Oct 4, 2005
  8. kidwoo

    kidwoo Celebrating No-Pants Day

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    Yeah I'm kind of wondering how much the twisty flex is attributable to bushing config. I know when you hit things head on with a shiver, it's not like it flexes....at all really. But it's the turning in the really rocky, lateral deflection arena that there was a big difference between the brands.

    Zedro is pretty much the size of your average ape on a skyscraper swatting airplanes so I'm sure he'll be able to tell the difference pretty quickly.
     
    #8 -   Oct 4, 2005
  9. trust4130

    trust4130 Monkey

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    I love the geeky stuff...

    Zedro, what FEA program are you using? I'm a structural engineer (PE in PA), and I'm curious about what software packages different people use for their analyses of bike frames/forks/etc.
     
    #9 -   Oct 5, 2005
  10. Tarpon

    Tarpon Monkey

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    It waw worth a try. I suspect that it's a bit more complicated than just adding another bushing. The clearances and lubrication path may need mods as well.

    What are Marzocchi bushings made out of?
     
  11. zedro

    zedro Turbo Monkey

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    i used CATIA V5 for the modelling and FEA....not the best simulation software but i just wanted to see if there'd be any change.

    They look like aluminum backed bronze with some kind of coating
     
  12. ChrisRobin

    ChrisRobin Turbo Monkey

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    Polish'em down with fine sandpaper.

    In the pic it looks like you'll have almost 9" of bushing overlap?
     
  13. Kornphlake

    Kornphlake Turbo Monkey

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    I'm not real sure how or where all those parts go when assembled, but what I'm seeing is 3 bronze colored rings seperated by 2 black spacers. Presumably these 2 spacers used to be 1 spacer but you chopped a seciton out using a dremel tool to give clearance for the added bushing in the center.

    If this is to all be pressed into the leg of the fork you really need to consider how you trimmed those spacers, the bushings appear to be split so they will slop around quite a bit as you press them into the leg of the fork, if the spacer wasn't cut perfectly flat it might tilt the center bushing and increase stiction. Maybe you're a lot better at cutting things with a dremel than I am, but I'd use nothing less than a lathe for a job like that.
     
  14. ohio

    ohio The Fresno Kid

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    I would suggest cleaning up the spacer on a lathe. Other than that, looks good and should definitely stiffen things up...
     
  15. zedro

    zedro Turbo Monkey

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    theres no way the bushings can tilt with the fit they had going in, not to mention they're 15mm wide. The spacers werent all that true to begin with, the precision from the lathe would be overkill IMO, the overall length was carefully judged by sanding in increments tho, but some had mentionned before that their bushings could jiggle in the stock setup (i noticed there was quite the allowance for the primary seal). Not concerned about the install.
     
  16. Kornphlake

    Kornphlake Turbo Monkey

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    Like I said I don't really know how this all goes together or how tight the clearances are. From an outside perspective I could see the bushing binding if it were tilted in the leg slightly, well that and I'm pretty anti-dremel for anything but artsy fartsy stuff.
     
  17. zedro

    zedro Turbo Monkey

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    yeah i never use it usually. I would normally use my bench sander with guide after chopping it but i didnt have access to my regular tools. Using tape as a guide, the cutting wheel and sanding it down on a table worked pretty good tho. But yeah, free-handing a dremel is almost useless for any type of finishing work.
     
  18. go-ride.com

    go-ride.com Monkey

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    I'm interested to hear about the results. My WP mx forks on my KTM came with a 3 bushing set up and the hot hop-up was to remove the middle bushing? Apparently with the WP forks the middle bushing can cause a type of hydraulic lock both making the fork feel choppy in rough and forcing oil out the seals. For riders that don't want to remove the middle bushing they recommend adding a groove or two or drill holes through the bushing to allow the oil to pass from the bottom of the upper leg to the top of the upper leg.

    Let us know what happens.
     
  19. ChrisRobin

    ChrisRobin Turbo Monkey

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    I seem to remember RockShox bushings for Psylo's (for example), had very slight grooves running the length of the bushing for oil flow.

    ...could of been hallucinating though...
     
  20. zedro

    zedro Turbo Monkey

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    the Shiver uses split bushings but also has a drillout on the stanchions to re-circulate the oil. But that is a good point,
     
  21. go-ride.com

    go-ride.com Monkey

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    The WP lowers have a hole in them too, but it was drilled to high up on the leg. Some guys drilled a second set of holes that were just above the the static bushing in the upper leg (ie: lower on the inner leg).
     
  22. toodles

    toodles Turbo Monkey

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    Yeah the bushings we use at my work come in either a plain option, a split option, or you can get them with either multiple straight grooves or single spiral grooves for lubrication.
     
  23. ohio

    ohio The Fresno Kid

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    If you say so, but with split bushings they can still misalign, even with that much outer surface to align them. You're probably right that it's just a break-in period...
     
  24. Rik

    Rik Turbo Monkey

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    I'd be interested in doing this mod next time I rebuild my Shiver, but I'd definately be cutting the spacer on a lathe just to satisfy my pedantisms. Let us all know how it goes, as it could give interesting results.
     
  25. Cave Dweller

    Cave Dweller Monkey

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    I bought a second hand set of 2000 monsters for spare parts. The upper bushing in one leg was not in straight and was causing stiction and wear on the ano surface of the stanchion.
     
  26. ATOMICFIREBALL

    ATOMICFIREBALL DISARMED IN A BATTLE OF WITS

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    -Zedro,
    Is this mod good.Seems good to me !
    How did it work out ?
     
  27. kidwoo

    kidwoo Celebrating No-Pants Day

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    Zed's dead baby.


    Zed's dead.
     
  28. zedro

    zedro Turbo Monkey

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    my contract with Marzocchi in celebrating the glory of the Shiver apparently extends into the afterlife so I've come all the way back to tell you that i have no clue because i haven't ridden that bike in a year and a half....unfortunately. But hopefully this summer, if i can get the hell out of hell....uhh i mean Virginia....
     
  29. kidwoo

    kidwoo Celebrating No-Pants Day

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    Virginia????
    Man when you move to the land of obesity, American Idol and NASCAR, you don't fvck around.:rofl:


    How's the freedom™ treatin ya?
     
  30. OGRipper

    OGRipper Turbo Monkey

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    Jeez man, you are all over Zedro today like a Jodie Foster stalker. Back off dude, just back off.

    :crazy:
     
  31. kidwoo

    kidwoo Celebrating No-Pants Day

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    He completes me.
     
  32. Duzitall

    Duzitall Monkey

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    Now come on Zed, please to do some curb hucking on the 3 bushed Shiver and let us know what up. I need to rebuild mine again soon.
     
  33. largextracheese

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    I was wondering where Zedro went? Where did you go mang?
     
  34. zedro

    zedro Turbo Monkey

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    burnout. You know. The usual.
     
  35. kidwoo

    kidwoo Celebrating No-Pants Day

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    Suckit pal.......I'll be 13 and a half in 2 months.
     
  36. Duzitall

    Duzitall Monkey

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    you're big boned and eat all your vegatables. Loved your pictures of Moab.
     
  37. ATOMICFIREBALL

    ATOMICFIREBALL DISARMED IN A BATTLE OF WITS

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    yeah, plz tell zedro.My Shiver is working perfect on my Bullit.
    But, i might do the 3 bushing thing if it's worth the time & effort ?