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DU bushing problems (help)

Discussion in 'Downhill & Freeride' started by demo 9, May 7, 2009.

  1. demo 9

    demo 9 Turbo Monkey

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    My 2005 demo 9 has been eating the bushings for my ROCO WC. I average about 2-3 runs before they totally wear out and get alot of play. I called marzocchi and talked to one of the tech people and he said that i need to get the 2 piece system instead of the 3 piece because my frame is pinching them wrong which makes them wear out, first off-any truth to this and secondly, where do i find the 2 piece system, i cant seem to find them anywhere
     
    #1 -   May 7, 2009

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  2. gonefirefightin

    gonefirefightin free wieners

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    specialized will have them
     
    #2 -   May 7, 2009
  3. klunky

    klunky Turbo Monkey

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    #3 -   May 7, 2009
  4. davep

    davep Turbo Monkey

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    Sorry, I forgot to respond to your PM.....:bonk:

    Anyways, IMO the guy at Marz is full of it or someone is mis-understanding someone else. I have never used, seen, nor heard of any instance, story, tale or recomendation that would suggest the el-crappo aluminum top hat style reducers do anything but shorten bushing life.

    What kind of bushings are you using? Steel backed DU or polymer? How are you installing the bushings? How are you installing the pin/axle? Are you lubing the bushings? Have you checked the thru axle/pin of the mounitng hardware for any rough spots or burrs? Is it orig hardware? Orig to frame or shock?

    At this point, the best mounting hardware that I have seen readily avail is the Vivid kit. Precision ground pin, two aluminum centering collars with o-rings to seal the bushing area http://www.bti-usa.com/images/thumbnails/large/rs/rs7411.jpg this is a much nicer set than Marz sells and it is 1/2 the price.
     
    #4 -   May 7, 2009
  5. Brian HCM#1

    Brian HCM#1 MMMMMMMMM BEER!!!!!!!!!!

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    Fox sells those, FYI.
     
    #5 -   May 7, 2009
  6. slowitdown

    slowitdown Monkey

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    wouldn't failure at 2-3 runs max indicate something is wrong in the rear half of the bike -- like some lateral or torsional movement of the back end, translating to stress at the eyelet bushings? or maybe a misaligned frame? or a bent or misaligned shock?
     
    #6 -   May 7, 2009
  7. davep

    davep Turbo Monkey

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    In one word, Yes!


    there are other less catastrophic possibilities, but yours is definately alive and well.....
     
    #7 -   May 7, 2009
  8. slowitdown

    slowitdown Monkey

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    just makin' sure I'm not losin' my mind.

    I haven't been here long but I see a ton of knowledge flowing from you dave. that's generous of you.
     
    #8 -   May 7, 2009
  9. EVRAC

    EVRAC Monkey

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    #9 -   May 7, 2009
  10. demo 9

    demo 9 Turbo Monkey

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    Sorry for the little delay, im picking up the bike tomorow from the shop(for other work) and im going to get pictures and make sure im talking about the right stuff with the correct names. All opinions are welcome as far as other ideas(such as frame damage) and stuff.
     
  11. Spunger

    Spunger Git yer dumb questions here

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    I had the cheapo ones that came with my 5th element and ate through them pretty quickly on my M1. I switched to the ones that Fox uses (bronze colored inside) and have had little trouble or issues with them. I have the 3 piece hardware for them.

    I did buy a DU bushing tool as trying to rig something up I didn't feel like doing. CTS makes a slick tool for DU bushings and you can do it all with 1 tool (remove the pin/replace the bushing) I think it was like $40 which is expensive, but what tool isn't?
     
  12. JCL

    JCL Monkey

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    Thought the Demo 9 had bearings in the rear shock eye/sub-seatstay mount ?
     
  13. demo 9

    demo 9 Turbo Monkey

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    OK, so ive got some pics to help anybody help me, it seems that the 2 fatter pieces are loose on the long piece, they fall off and can jiggle around. When in the frame i see them moving and they get about 1-2mm of play (at the seat). The long piece in the shock itself is pretty snug but i can "twist" it a very little amount. (mayb i should replace that also?) i did not use any tools to put these in or out, they seem pretty easy to do by hand.





    Can i ride these tomorow without causing any more damage to the bike or shock?
     
  14. Spunger

    Spunger Git yer dumb questions here

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    That is your problem right there. Those aluminum spacers aren't suppose to move at all. They should sit flush with the DU and the mounts. That play is allowing things to move and not stay centered.

    If you could rig something up to take that space up then you might get it worked around for a bit, but the correct fix would be new spacers and a pin that are the correct size. I'm sure the pin is, but those spacers aren't..

    If you can put the pin in by hand with a new DU bushing then the pin is worn and needs to be replaced. A tool should be necessary to get that pin out. Mine when worn just fall out, but when new they go in with a tool only. I couldn't get them to budge in by hand unless I was the hulk or something.

    Anything DU related on a rear shock should not press in by hand period.
     
  15. uncle-mofo

    uncle-mofo Chimp

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    They'll be fine to be ridden for a day, mine have been loose for more than a year now and I've been lazy about changing them. I find it hard to justify upwards of 25 euro for those little pieces.
     
  16. illflip

    illflip Monkey

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    you might have some play between the mounting bolt and the "long piece".

    reading your post reminded me of the little play i have on my frame(R9), so i checked my bushings. My bushings on my lower eyelet are worn out as well, and i discovered the play between the bolt and the long piece. the bshings on my top eyelet are snug, and dont have any play.
     
  17. davep

    davep Turbo Monkey

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    The spacing collars do seem a bit short. They should have just a hair of space (be lightly snug) when everything is tightened up in the frame....if they were truely tight (side to side) when everything was bolted up, they would bind the shock. This is again one of the benefits of the Vivid hardware as the collars have o-rings that face the shock eye to prevent metal-to-metal contact and keep dirt out.

    The pin should not go in by hand, although I doubt the pin itself is worn as it is stainless and runs against urethane (or lead infused copper if the bushing is badly worn). Sounds like a lightly worn (but not very bad) bushing. Really worn bushings will allow the pin to fall right out and it will feel loose in the shock.

    Illflip also mentioned something worth checking. It is not uncommon on the demo (because of the forged parts) to have issues tightening the bolt to be able to properly pinch the pin and make it tight in the frame. IIRC spec had some very thin shims to help take up side to side slack on the front mount...you could also source something yourself via mcmaster if you need.
     
  18. demo 9

    demo 9 Turbo Monkey

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    so im still kinda lost on this stuff, what should i buy to replace it and will that work? i dont completely understand how the system works and why (for me) it goes so quickly
     
  19. pain

    pain Monkey

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    have a shop machine you a pair out of some hard steel.
     
  20. dilzy

    dilzy Monkey

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    The pin should most definetly go in by hand, or it will gaul. It is a very fine line with bushings between gauling and slop.

    Those spacers are not nessesary to the bushing. In most cases, frames are not built perfectly in line, so the shock is being forced into line by those spacers. Take them out, go for a little spin down some stairs (just to cycle the rear end a lot) and then look where the eyelet of the shock ends up. Most bikes it's off centre, indicating frame miss-alignment.

    Most of the slop you speak of I can almost guarantee will be because the bolt is lose in the pin, not the pin loose in the du bush. There is nothing you can do to solve this except get a custom bolt made that is a tight fit. No amount of tightening will solve it.
     
  21. davep

    davep Turbo Monkey

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    It is galling and although the formal definition seems to allow for what you are describing, it generally refers to near-same material issues that result in cold welding type results. Scratching a plastic coating with a piece of rough metal would not be considered galling IMO.

    Either way, if the pin is smooth as it should be, a careful press fit is quite possible and will result in the best/longest lasting interface with near zero DU removal.

    All shock reducing hardware on every frame is larger ID than the bolt OD that it fits on. Unless you are refering to custom shoulder bolt hardware (threads are larger than OD of a 'normal' bolt thus there is no way to slide a part on to a bolt and have it 'tight')), there is no realistic way to find or have made a pin that will fit radially tight to the mounting bolt. The frame should/is designed to flex enough at the mount point to 'pinch' the shock pin/mount hardware...preventing all movement of the shock hardware (pin) in both the radial and axial directions. THe demo 9 uses a very thick, very stiff forged cage that suppports the shock mount area. Because of this design, the frame is not able to flex enough to pinch the shock mount pin. This resuts in pin movement on the shock mounting bolt.

    I would agree that it is highly likely that you have thiss issues, however, there are several things that can be easily and cheaply done to solve/eliminate this problem....


    Demo, solving this (like any other problem in life) will take a systematic approach. You will need to test and eliminate the possibilities.

    First, I would mount just the pin in the frame and torque to spec. If you can move the pin in any way even with some difficulty, you definately have an issue with the pin being too short for your frame application. Find either the spec frame shims for this exact issue, or a slightly longer pin that will be long enough to be properly pinched in the frame...contact Spec about this!

    I would also suggest new hardware (I won't mention my preference AGAIN) and a new bushing (instal/removal will wear the DU) as preventative work as well as simply better parts.
     
    #21 -   May 11, 2009
    Last edited: May 11, 2009
  22. dilzy

    dilzy Monkey

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    I suppose galling isn't really the right term, but I have had the coating wear from the DU as a result of too tight a pin. It should be a H7-G6 clearance.

    I was refering to having a threaded bolt that is a locating fit in the pin to secure it to the frame. Pinching the frame to hold the pin tightly transfersly to stop radial slop around the bolt is a band-aid for a knife in the chest.

    Mine slops and frankly I couldn't give a rats, but if you want to get ride of any slop, that's the only way to do it properly.

    My final suggestion to the OP is to put the pin in a drill (if you don't have access to a lathe) and give it a light going over with 600 grit, then a good polish until it's a nice smooth push fit with some lubrication into the du bush.
     
    #22 -   May 11, 2009
    Last edited: May 11, 2009
  23. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    I agree with davep. The pin should not go in by hand, and I think you're wrong about the bolt too dilzy. Clearly if the pin is quite a loose fit in the shock or even slides in and out by hand then it is wear on the DU bushing.

    The bolt/nut assembly just clamps the frame against the reducer (that slides through the shock eye). Once the frame is clamped adequately against either side of the reducer, even if the tolerences between the bolt OD and reducer ID aren't ultra tight, there will be no play.

    Another thing to throw in, what everyone generally calls a DU bushing isn't a DU bushing to my knowledge. DU = black inner coating. DP is the bushing type that most shocks use (fox, RS, etc). You'll notice the part number on the stock fox part is 08-DP-08. Unfortunately they're harder to find aftermarket, but they seem to last longer and the coating appears to be of higher quality than the black ones.

    Also, davep, you're wrong about the vivid hardware to my knowledge. I've had two vivids on two bikes (09 v10, 09 sunday) and the o-ring doesn't actually sit against the bushing / shock eye. Therefore it doesn't really seal the bushing from anything, it just makes the system go together nicely without spacers falling off while you assemble. The later fox shocks on the other hand use spacers with an x-ring that actually sits against the eyelet/bushing and correctly seals the bushings. You'll have them on your 07+ sunday.

    I don't really think that it matters a whole lot, but I just thought I'd throw that in having owned multiples of both shocks and hardware.
     
  24. dilzy

    dilzy Monkey

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    The OP said the pin was a very tight fit. If you have to put it in with a press/hammer/vice, then it's too tight.

    The clamping friction between the pin and the frame will not be sufficient to prevent movement. Discounting bottomout forces, just full compression of the spring will put 5+KN on the pin and that small amount of clamping on the pin is not enough to hold it properly and will gradually loosen.

    It doesn't really matter when your riding, but lifting the seat gives the sensation of bushing slop.
     
  25. demo 9

    demo 9 Turbo Monkey

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    the frame bolt is kind of "loose" in the long piece, and the long piece is loose in the shock itself, what im wondering is could the inside of the shock be worn? the long piece seems to be perfectly flat and not worn
     
  26. dilzy

    dilzy Monkey

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    Right, up the top you said the pin was tight in the bush. If you've got access to some verniers (calipers) and could measure the pin, that would be very helpfull.
     
  27. demo 9

    demo 9 Turbo Monkey

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    i can get the pin measured tomorow or the next day, i just dont want to go and order new bushings (or whatever this stuff is called) and have it wear out super fast. what im thinking is that even if i get a new pin and the 2 barrel pieces, the shock will still be loose because of the bolt.
     
  28. illflip

    illflip Monkey

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    dont think the two barrel pieces matter too much. getting the right length pin to fit snug in between the frame will probably help a lot.
    if the pin is just falling out of the eyelet on it's own, then get a new bushing.
     
  29. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    No, he said it was fairly snug but he can twist it around. Take any brand new shock with 3pc reducers fitted, you cannot twist the reducer by hand. Often if you can move it around by hand in the shock, it can translate to some amount of play on the bike. Am I missing something, or have you never installed hardware in a new shock? You're not getting that reducer into that DU bushing without a press of some description.

    I also disagree with your claim that the clamping force of the bolt is insufficient to prevent movement. I've had plenty of frames where the tolerence between bolt and reducer is less than perfect, but when done up there has been zero play (and zero play has developed). The forces generated on rebound stroke are much lower than those on compression and therefore if you do up the bolt with the bike compressed a little then nothing should move in use. If there is play in your frame, something is wrong and that something should probably be addressed if you don't want to accelerate wear on components other than ones designated to wear (in this case it should only be the DU bushing).

    Having read through everything again, I'd say the problem is likely one that davep touched on of the frame not actually clamping against the reducer properly. Purely due to that, the play between the bolt and reducer may have become evident.

    demo9 -
    I would suggest getting a new DU bushing installed if the long piece (reducer) is loose inside the shock; and if after that you install the shock and there is still play (after doing up the bolt/nut assembly quite firmly), then you will need some small shims to go either side of the existing reducer (they will sit between the frame and reducer) OR get a new reducer that has a tighter fit in the frame (and replace those two spacers while you're at it, because they seem to be on the short side). Make sure when they replace the DU bushing, that they use one with the red coloured material on the inside - if it's black it tends to wear faster.
     
  30. demo 9

    demo 9 Turbo Monkey

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    Last night i ordered a new bushing kit, i got 1 long piece and the 2 barrel pieces. also it doesnt get play side to side, it gets play up and down. that means that it IS NOT the frame? its quite a pain to get the shock into the frame because of how tight it is(the long reducer) and the frame width. after everything comes in i am going to see where there is play and work from there. If there is still play does that mean that the super skinny piece IN THE SHOCK is worn out?
     
  31. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    Yeah we understand the play is up and down. It shouldn't be anything wrong with the frame.

    By the way, that one long piece is called a reducer and together with the two barrel pieces can be called reducers (or you can call the two barrel pieces spacers). The thing to note is that none of those parts are bushings - a bushing is a wearing part. That is the "super skinny piece" that you can see inside the shock eyelet, that bushing is actually replaceable and it might be a good idea to get a new one popped in along with your new reducers when you get them. A shop can do it for you, shouldn't cost much.

    By the way, if your new stuff doesn't fix it, I'd advise very carefully trying to figure out exactly what part the play is coming from - only you can do this. See if there is play between the shock eyelet and the reducer+spacer combo OR if there is play between the reducer and frame - rock the back of the bike to create the play and use your finger on the parts to see what is moving. That way we can tell you what to fix, otherwise it's just going to be guessing like it has been so far.