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2011 Fox 40 FIT Issue

Discussion in 'Downhill & Freeride' started by Routier07, Dec 24, 2014.

  1. Routier07

    Routier07 Monkey

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    Happy Holidays Everyone!

    I just inherited a friends' Fox 40 that he had sitting on a shelf for the past few months...

    I've taken the fork apart to regrease the seals and all. During the inspection of the damper, I've noticed that it hits kind of a wall at the last inch of travel, the HSC, LSC and Rebound are all wound out(open) and the problem once gets worst if I tune the settings in 3/4 to full.

    I know that a couple of you have quite abit of experience with Fox 40s and I'm needing some help with this.

    Cheers!

    Louis R.
     

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  2. bengxe

    bengxe Monkey

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    Sounds normal. That's the hydraulic bottom out control. I'm pretty sure it's adjustable internally if it really bothers you.
     
  3. Routier07

    Routier07 Monkey

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    Thanks for the reply Bengxe!

    That's what I thought, but it feels more like it catches on something inside... I've taken the oil out of the cartridge, and it has a catch 1-1.5inch before bottom out. Im wondering if something has worked itself loose on the inside...

    Cheers

    LR
     
  4. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    That is completely normal, it would seem strange to someone who has not worked with those dampers before. It should feel like it catches, and then has a higher amount of friction further into the stroke, which is released once the piston is removed from that stroke region.

    The hydraulic bottom out uses a small piston with a glide ring that fits very tightly against the receiver that it enters, it needs to be a (very) tight fit to provide the level of sealing needed to build up pressure in the assembly. The sliding friction at that point in the travel is insignificant compared to the high spring force developed in the last ~inch when the fork is in real-world use.

    As a side note, it's no longer adjustable on the newer inverted dampers (2011+) and is eliminated completely in 2014+ air sprung forks. In my experience it's not necessary (even on coil forks) if you are running the correct spring rate and level of compression damping for your body weight and skill level - however most people aren't, so it's a good fail-safe.

    http://www.peterverdone.com/?p=314
    If it really bothers you, you can remove it as per this article. I don't fully agree with him claiming it's an important adjustment (it's not really), although on the 36 it does tend to limit travel use (since it is active for a similar amount of actual stroke as the 40, even given 2" less travel). It's not really a problem on the 40 and might be handy if you are hitting big jumps/drops.
     
    #4 -   Dec 24, 2014
    Last edited: Dec 24, 2014
  5. Routier07

    Routier07 Monkey

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    Udi, Thanks for all that great information!!!

    I can clearly see whats going on now, its good to know that nothing is actually broken or needs replacement. In your opinion, if I'm not a jumper or don't do any big drops, do you suggest I just cut out that small piston at the very top of the rebound damper??

    Thanks again!!

    Happy Holidays!

    Cheers
     
  6. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    I don't really think there's a huge need to remove it, I'd just assemble the fork and ride it and then change it later if you are not happy. I only found it a problem in the 36 where it is active for too large a percentage of the travel, that's not the case in the 40.

    Remember to use Fox Red (or Silkolene RSF 10) in the damper, and ideally Fox Gold in the lowers. I recommend 60-65ml per leg for lower lube over the factory 50ml - longer bushing life and a bigger buffer for contaminants.
     
  7. Routier07

    Routier07 Monkey

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    Sounds Perfect!!

    If I cant easily get my hands on Fox Oils, What would be a good enough substitute for Fox Gold for lowers use??

    Thanks again for the help Udi!

    Cheers

    LR
     
  8. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    No problem!
    For the lowers the Gold is worth getting if you can find it (it is a custom formulation that sticks to surfaces much better than regular oils), otherwise I've found Motul "Expert" 15wt to offer reasonably good results. Hopefully you can get the Motul and Silkolene products.

    My posts below provide further information on oils if you are interested.
    Posts 16, 21 here:
    Damper oil
    Posts 211, 214, 217, 221 here (excuse the arguments):
    Damper and lubrication oil
    I use the abbreviation VI a lot (w.r.t. damper oils), if you need an explanation:
    Wikipedia - Viscosity Index