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Signs your FIT RC2 damper needs a service/rebuild

Discussion in 'Downhill & Freeride' started by csermonet, Apr 30, 2014.

  1. csermonet

    csermonet Monkey

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    I have a 2011 Fox 40 and recently did an oil change on the lowers. While I had the fork apart, I cycle'd the damper side rod through its travel. When it got to the last ~15% of its stroke, you could feel a very slight "notch". I doubt it would be noticeable while actually riding. I haven't noticed any weird effects on the adjustments or anything, and I wasn't sure if the oil was possibly changing through a circuit or blowing through the shim stack or something in the travel thus causing the "notch" feeling(I am not up to speed on how the internals work exactly, plan on learning though.) Is this indicative of needing a service? I have no idea how many actual ride hours are on the fork, it was on the bike when I bought it and very lightly used. I know I personally haven't put more than 50 hours on it for sure.

    On another note..every time I change the bath oil, the spring side is extremely dirty when compared to the damper side. The damper side always comes out the same color that it went in, meanwhile the spring side comes out tinted pretty black. Any one else experience this? The original ti blue spring that came with it, snapped the seat off and had the blue coating worn off pretty bad. Wondering if that's whats accumulating in the oil? i've had a green ti spring with a long section of shrink wrap applied to that would hopefully keep it from wearing the coating off inside the stanchion.
     

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  2. canadmos

    canadmos Mater Slayer

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    I'm not sure about the notch feeling, but I do know that my Fox forks, as well as my friends, all experience the same thing with the spring side oil becoming dirty faster than the damper side. I have always just assumed it was from the spring rubbing around on the inside or from deterioration of the shrink wrap on the spring..
     
  3. tacubaya

    tacubaya Monkey

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    The notch feeling is probably the hydraulic bottom out engaging.
     
    #3 -   May 1, 2014
  4. csermonet

    csermonet Monkey

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    Thanks for the replies dudes.

    So can anyone tell me what some symptoms would be of needing a damper service? I know the manual says every 100hrs but just wanted to know if there would be any physical affects attributed to it.
     
    #4 -   May 1, 2014
  5. Steve M

    Steve M Turbo Monkey

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    As Tacubaya said, what you're feeling is the hydraulic anti-bottoming system engaging, it's nothing to be concerned about.

    If you're waiting until your damper has "symptoms" that physically tell you that it needs a service, then usually you're no longer performing a service, you are now performing a repair. With that said, however, FIT cartridges almost universally either lose oil or gain oil slowly over time - this is why the older non-inverted forks used to blow the bladders out the bottom after they slowly sucked enough bath oil into the damper. At a bare minimum, each time you drop the lowers to change the bath oil, you should be pulling the cartridge out of the fork and checking that the bladder is in a neutral state - if, when fully extended, it looks "dehydrated" or it's distended (ie at all stretched/pressurised), your damper needs some love. If it's lost or gained a substantial amount of oil in a short period of time, replace the seal head, otherwise a rebuild, inspection and bleed may be sufficient, as the Fox seal heads are not quite as perfect a seal as they perhaps should be - even from brand new they will slowly allow slight ingress/egress of oil.
     
    #5 -   May 1, 2014
  6. csermonet

    csermonet Monkey

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    Thanks for the response Steve. I have the full rebuild manual from Fox, I'll check it out and see what all is involved. I always planned on learning to service the damper myself, sounds like it's a good thing to be able to do yourself. Hopefully not too many proprietary tools are required.
     
    #6 -   May 1, 2014
  7. Steve M

    Steve M Turbo Monkey

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    The inverted Fit RC2 damper doesn't require special tools other than the correct size shaft clamps and a Mixmizer syringe (available from Walmart for about $5, or here http://www.enduroforkseals.com/id38.html), which are by far the best syringes available for use with suspension. Fox sell the shaft clamps for a fairly silly amount of money, but Barnett Bicycle Institute make an awesome set that will cover 99% of stuff you'll ever service.
     
    #7 -   May 2, 2014
  8. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    You don't really need the shaft clamps if all you are doing is a bleed / oil change, I find they're only necessary for a valving change. You can probably rig up something to hold the cartridge sufficiently enough to bleed it if that's all you need to do, just don't crush the tubes. A single circlip allows access to the oil from the top, at which point the syringe recommended above (and appropriate rubber sleeves to seal it to the cart) is all that is needed.

    Don't forget to use the right oil - Fox Red, or Silkolene Pro RSF 10wt @ 47cSt / 300VI. It's a shock oil because the damper is similarly low volume and requires it.
     
    #8 -   May 2, 2014
  9. mtg

    mtg Green with Envy

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    The shaft clamps are pretty easy to make, BTW. I made a set years ago from two pieces of 2x3 wood, clamped them together and drilled holes with forstner bits.
     
    #9 -   May 2, 2014
  10. csermonet

    csermonet Monkey

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    Awesome, thanks guys. I think I will cut out a clamp with some wood blocks to just be able to bleed it. Sounds like its not too bad of a job.
     
  11. blindboxx2334

    blindboxx2334 Turbo Monkey

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    just briefly read over this thread and didnt see any mention of a mixmizer.

    if you dont have one, get one. near impossible to get all the bubbles out if you dont have something similar to a mixmizer.
     
  12. bengxe

    bengxe Monkey

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    Post #7
     
  13. blindboxx2334

    blindboxx2334 Turbo Monkey

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    nice! i did indeed miss that.
     
  14. Happymtb.fr

    Happymtb.fr Monkey

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    I just found an old 36 rc2 on the Craig list and guess what? The bladder on the damper was shot!
    Part number 210-22-106 for the bladder does not appear to give any hit from online retailer... do you know if there are still spare parts available for inverted fit cartridges?
    And while I am at it, what else should I change?
    The rebound glide ring PN 002-02-011 and probably the seal head but I cannot find any part number for it here: http://service.foxracingshox.com/consumers/Content/Service/Forks/36FLOAT/36FLOAT_RC2.htm
     

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  15. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    That's the old pre-invert damper (designed in 2005), vastly different to what everyone is talking about in this thread. It's a known issue where the bladder will blow on those (like that), and often there is physical deformation of the housing and base when it happens (not always visible).

    I'd personally not even bother, it'd be better to run a newer 36 with the inverted FIT cartridge. If you must though, the bladders usually pop up for sale here and there - occasionally ebay, maybe try enduroforkseals, or even emailing TF or Push.

    In terms of what other seals to replace, I've had the LS/HS adjuster o-rings fail before so you can replace those if desired but they are a pain to get to. Usually not necessary, just annoying if it happens after a rebuild. It's also worth nothing these old dampers have less compression damping than newer forks, so doubling the face shim on the compression stack helps. It's not a standard size unfortunately.

    On these, the assembly process is critical to how long the rebuilt damper will last. It's important to make sure the bladder doesn't have any deformation during assembly and is completely free of oil internally. After bleeding and tightening down the nut, I unscrew it again, clean all threads with isopropyl, and use red loctite for final assembly.

    If you're wondering why the design was changed (external bladder in 2011 onwards), it's because the internal bladder has a finite max volume, and any air (or bath oil) ingress into the damper over time decreases this finite volume. This means that the damper starts generating high internal pressure near BO and eventually blows up.
     
    #15 -   Mar 31, 2017
    Last edited: Mar 31, 2017
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  16. Happymtb.fr

    Happymtb.fr Monkey

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    Thanks for the info!
    I don't have to but I think it is a cool project, a good way to get my hands dirty and learn something ;)
    I've got a Marzo 66sl from 2006 for almost nothing 2 years ago and put it back together. It was fun and I quite like the forks. We will see how the 36 will perform in comparison.

    Do you know how I could date the 36? It should be pre 2010 tho. It has kashima stanchions, 20mm axle, straight steerer and PM brake mounts.

    I have found that service kit 803-00-149 might be right for these forks... I will check with the local Fox dealer after the weekend.
     
  17. Happymtb.fr

    Happymtb.fr Monkey

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    I will have a look at it.
    If I cannot find the right size, what about running slightly thicker oil instead?
     
  18. Flo33

    Flo33 Monkey

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    That's the right kit. eBay is your friend.
     
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  19. djjohnr

    djjohnr Turbo Monkey

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    I may still have a rebuild for that lying around if you need one
     
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  20. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    Yeah that'd work OK - only concern is the stock oil is already quite thick, and you need a high VI fluid (for reasons explained earlier in this thread). It's Silkolene Pro RSF 10wt which is 47cSt, so you could run Pro RSF 15wt if it's still available, or find something with similar specs. It would have to have a cSt of 60+ and a VI of >270 or so. The doubled face shim (or thicker face shim) is definitely preferable though.

    RE: dating it - post up a pic. It sounds like an old damper retrofitted to a newer fork, as those dampers ceased production in 2010 and kashima began in 2011 (coupled with the new inverted FIT cartridge).

    They are a good damper functionally and can be sufficiently reliable if built carefully.
    Details of shim sizes here.
     
  21. Happymtb.fr

    Happymtb.fr Monkey

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    Thanks, a lot of information here! :)

    Here is a picture. I'm not quite sure it is kashima coated after all... there is no kashima inscription below the crown.
    20170401_130036.jpg
     
  22. Happymtb.fr

    Happymtb.fr Monkey

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  23. Lelandjt

    Lelandjt Turbo Monkey

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    Not Kashima. Pre-2011.
     
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  24. Happymtb.fr

    Happymtb.fr Monkey

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    I managed to open the cartridge and access the shimz :banana:
    They look kind of corroded, I suppose I need to get new ones on top of the extra face shims. What do you think?
    20170401_174425.jpg
    I will have to make some wooden shaft clamps in order to access the compression piston and the rebound assy
     
  25. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    That's a 2009-2010 year model, non-kashima.

    For the shims you can just scrub them a little over some 1500-3000 grade sandpaper to clean them up, no real need to replace. Keep in mind their permanent oil submersion.

    Also I've never really seen a worn rebound glide ring personally so there's no real need to pull apart that end of the damper either unless you really want to. The seal head uses a thick o-ring too, everything in the top half of those dampers is generally quite durable.
     
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  26. LAP

    LAP Chimp

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    I might have a bladder from a 2008 36 damper. Don't know if they are the same though.
     
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  27. Happymtb.fr

    Happymtb.fr Monkey

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    Thanks again @Udi !
    I wonder, are you a bike mechanic to have such a deep knowledge of bike parts?

    About the rebound, it is definitely working since I tested it before tearing down the fork. I will follow your advice and leave it like it is. Turning the compression knobs did not make any noticeable difference so that I am going to check if the compression piston is flat like discussed in the other thread.

    Thank you @LAP and @djjohnr for offering your spare parts! I am located in Sweden so that shipping would be rather expensive and it seems that the service kit is available in Finland. I might come back to you if I cannot source it locally tho.
     
  28. Happymtb.fr

    Happymtb.fr Monkey

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    The compression piston is dished like if the expulsion of the bladder drew on the compression assembly. It's 0,3mm higher at the centre.
    It is the side of the check valve that needs to be flattened, isn't it? Since the compression shims are pushed by the coupler.
     

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  29. LAP

    LAP Chimp

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    No problem! Page me if you end up not finding one locally.
     
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  30. FarkinRyan

    FarkinRyan Monkey

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    If anyone is indeed still looking for bladders I have plenty and shipping worldwide (from Canada) is not ridiculous for such small parts, can't imagine it would be more than $15 to Europe.
     
    #30 -   Apr 4, 2017
    Last edited: Apr 5, 2017
  31. Happymtb.fr

    Happymtb.fr Monkey

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    I've now got all the necessary parts for building the old 36 back into shape. :)

    Something strikes me: the compression assy of a 2015 and onward RC2 looks extremely similar to what I see on the old one (from 2009 or 2010). Especially the compression piston, the 4 shims and the coupler mechanism.
    Since the old shim stack was too weak, I don't quite understand how the same shim stack with now lighter oil can give enough damping? Did Fox compensate with a stiffer preload spring? The diameter of the rebound shaft seems also quite similar between both models...
    The pictures attached are from the old fork and the drawing is from the 2015+ RC2.
     

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    #31 -   May 10, 2017
    Last edited: May 11, 2017
  32. Flo33

    Flo33 Monkey

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    How old is old? Pre inverted <2011?
     
  33. Happymtb.fr

    Happymtb.fr Monkey

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    Yes. Udi dated it 2009 or 2010
     
  34. Flo33

    Flo33 Monkey

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    Spring is the same, 90 lbs/in. Even same part number.

    You might be up to something here... @Udi care to join?

    Tftuned did change it during a PUSH tuning in my 2006 RC2 damper in 2009, into a weaker one. I was complaining about bad small bump compliance in the gen1 TALAS 36. Didn't help.


    BTW, can somebody elaborate which model year this fork might be?

    https://www.pinkbike.com/buysell/1851893/

    It clearly is not a 2012 model, no Kashima present. 2011 had no grey lowers, but there is an inverted cartridge, so at least that part is post 2010. I'm confused.
     
    #34 -   May 11, 2017
    Last edited: May 11, 2017
  35. Happymtb.fr

    Happymtb.fr Monkey

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    Sorry Flo, I am too much of a noob for helping you out there... I hope some knowledgeable guys will shim in!

    My fork is upp and running now! I'd forgot how much fun HT can be. :) I run it at 130mm and doubled the 2 largest shims which, so far, seems almost too much since I backed off the HSC almost completely.
     

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  36. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    Kashima was only for the high-end 36 so you could still get the non-kash in later years, but those lowers look like 07-08 to me. CSU looks newer, and the damper has to be at least 2011.

    FYI a fork never has to be from one single year. I'd probably avoid ones that aren't though.

    Nice work Happymtb.
     
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  37. Happymtb.fr

    Happymtb.fr Monkey

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    Thanks for your help!
    No comment about post #31? @Udi
     
  38. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    Yeah, nice detective work Watson. Keep looking for clues and you'll solve the mystery. :)

    Hint: the deflection or travel of a shim somewhere is restricted on the new damper.
    I haven't compared the spring rates so am not sure if that changed as well.

    Nothing to do with the oil, that only changed for the most recent damper (2015-2017). Inverted FIT still used Pro RSF10 for 4 years (2011-2014), the valving changed with the oil in 2015.
     
  39. Happymtb.fr

    Happymtb.fr Monkey

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    Ok, thanks @Udi
    I will keep looking ;)

    By the way, are they different spring rates for the negative spring of Floats from 2009-2010?
     
  40. Flo33

    Flo33 Monkey

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    No. That's a drawback of that design.


    I checked on the comp preload spring, it even has the same part number in the official Fox documents, 039-00-065.

    The RC2 Preload Hat is also the same part, 210-22-249.

    Only difference I could spot is the piston. :brow:
     
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