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  1. #1
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    Question about Fox fork red/green oil

    Hey guys,

    I have a Fox 32 Float 120 FIT RLC 15QR from 2011 (I believe), that has had the travel reduced by the original owner from 120mm to 100mm. I would like to return it to the original travel. I believe there's just a plastic spacer inside the fork, on the air spring assembly. I'm confident that I can disassemble the fork and remove the spacer by myself. (Not forgetting to put it back together as well )

    My question is, however, what oils can I use to replace what's inside the fork now? There are no Fox dealers around where I live, nor would I like to order those terribly high-priced big containers of Fox fork oil for just this little job.

    The manual says that I should use:
    FOX Red 10 wt. - Damper - 30.4ml
    FOX Green 10 wt. - Damper-side/Spring side oil bath - 30.0ml
    FOX Float Fluid - Air Chamber - 5.0ml

    Couldn't I just use any enduro etc. motorcycle 10wt. fork fluid instead of the Fox Red and Green stuff? If both oils are 10wt, then what's the difference between the two?

    Also, what sort of oil is the Float Fluid, and can I use something else?


    I understand that this has been asked many times and I've read the other threads, but there wasn't any major conclusion to this and they were talking about older forks.

    Thanks in advance!
    Last edited by Patuman; 07-03-2013 at 10:06 AM.

  2. #2
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    The red goes in the damper, the green goes in the legs so you just need the green 30ml each leg. Not sure about motorcycle oil etc but probably fine.
    Float fluid is much thicker, its cheap for a 5ml pillow pack, just get one.

  3. #3
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    Motor oil has been recommended for the bath oil. I used it for a year in my Fox FIT fork and it worked well. It's a little thicker than Fox green oil and lubricates the stanchions well.

    For the Float fluid, some people substitute 90w gear oil. I've always used float fluid.

  4. #4
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    The main differences between Fox 10wt Red and 10wt Green are the lubricity (how well it lubricates) and the viscosity index (how much the viscosity changes as the oil heats up). Oil "weight" is a silly measurement of viscosity as one brand's 10wt can be another's 5wt, the value you really need to know is the kinematic viscosity (measured in centistokes, or cSt) at 40 degrees celsius (one of the two standard temps for measuring viscosity, the other is 100C which is much hotter than fork dampers usually get). A good chart for comparing between brands can be found here: http://www.peterverdone.com/wiki/ima...osity-Data.gif


    What it boils down to is this:
    10wt Red is an excellent DAMPING fluid because of its high viscosity index. This makes it particularly suitable for rear shocks (which can run at surprisingly high temperatures) and low volume fork cartridges (Fox's FIT carts) because its viscosity does not change much as it heats up. This fluid is fine to replace with most other brands' equivalents, meaning ~47cSt @ 40C and a VI of 300+. However, it is not recommended as a bath oil, as its lubricity is not particularly amazing, so don't go putting it in your lowers.

    10wt Green has a lower viscosity index than the Red, but has much better lubricity. This means that it is very slippery, and excellent for dampers with high volumes (such as open bath lowers requiring oils of this viscosity), or lubricating fork lowers (in fact, it's what I use in all fork lowers unless a particular open-bath damper requires a different viscosity fluid, such as Marzocchi dampers). There is no unit of measurement for lubricity, which means it's 100% trial and error to find something suitable. This makes the Green fluid harder to replace with other brands' alternatives, and I am yet to try any fluid that I have found to be slipperier. I would highly recommend using it where Fox say to.

    As for Float fluid, I again recommend using only Float fluid and not a replacement, as its viscosity and constituency is not made known to the public, but it works exactly as it is intended to - it is a very good lubricant for air piston seals.

    To summarise: you will have no problems subsituting the Red fluid with any other brand's equivalent high-VI oils with a comparable viscosity (again, around 47cSt), but the Green and the Float fluids are quite specialised and attempting to replace those is not something I would personally recommend. I realise they are expensive, but they are the right tool for the job.
    VorsprungSuspension.com - fully engineered suspension retuning & servicing in Whistler, BC.

  5. #5
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    Quote Originally Posted by Steve VS View Post
    The main differences ........
    Well that about sums it up. Fox recommends their oils for a reason. They are designed with a particular use in mind. Normal motor oil is cheaper but is designed with a different purpose in mind.

    Go with the fox. My .02

  6. #6
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    So, bringing up this old thread but I've got a question about the opposite usage of oils, has anyone used the green Fox fluid instead of the red for the damper? I've changed the oil several times in the fork lowers, along with dust seals/wipers.

    Now, my damper is making an awful rattling, making me think the oil is no longer there, or severely low. If true, and it's dry, I'm thinking green oil might not be as ideal as red, but would be better than the damper being dry.

    Or, maybe I'll just buy the entire seal kit and a bottle of red oil and rebuild the forks the proper way.

    Any feedback with experience is appreciated. My LBS only has the Fox 20W Gold oil in stock.

    Thanks!

  7. #7
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    Quote Originally Posted by Tillers_Rule View Post
    So, bringing up this old thread but I've got a question about the opposite usage of oils, has anyone used the green Fox fluid instead of the red for the damper? I've changed the oil several times in the fork lowers, along with dust seals/wipers.

    Now, my damper is making an awful rattling, making me think the oil is no longer there, or severely low. If true, and it's dry, I'm thinking green oil might not be as ideal as red, but would be better than the damper being dry.

    Or, maybe I'll just buy the entire seal kit and a bottle of red oil and rebuild the forks the proper way.

    Any feedback with experience is appreciated. My LBS only has the Fox 20W Gold oil in stock.

    Thanks!
    It's pretty common to use Fox green in the damper. I've worked on many shocks which have been filled with green at prior service. The open bath dampers used in the earlier fox forks (150-160cc of oil in the damper side) ran green.

    The viscosity index of green is fine for pretty much all mtb suspension applications. If you ever have issues with oil fading from heat then you'll know and it's time to move to a higher VI fluid. But that's extremely rare.

    The red oil has changed since Fox first changed to it. Previously it was rumoured to be Silkolene Pro RSF 10. This was a damper fluid that doesn't lubricate well and doesn't like air either. But worked great in sealed dampers.

    Silkolene/Fuchs have recently reformulated, it's now called RSF10 with emphasis on "suspension fluid" instead of shock fluid. It is now slippery enough to use in forks as well as shocks. Fox have changed their recommendations accordingly and replaced green with red in their recent oil charts.
    Owner of www.shockcraft.co.nz and NZ Manitou Agent.
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  8. #8
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    Quote Originally Posted by Dougal View Post
    It's pretty common to use Fox green in the damper. I've worked on many shocks which have been filled with green at prior service. The open bath dampers used in the earlier fox forks (150-160cc of oil in the damper side) ran green.

    The viscosity index of green is fine for pretty much all mtb suspension applications. If you ever have issues with oil fading from heat then you'll know and it's time to move to a higher VI fluid. But that's extremely rare.

    The red oil has changed since Fox first changed to it. Previously it was rumoured to be Silkolene Pro RSF 10. This was a damper fluid that doesn't lubricate well and doesn't like air either. But worked great in sealed dampers.

    Silkolene/Fuchs have recently reformulated, it's now called RSF10 with emphasis on "suspension fluid" instead of shock fluid. It is now slippery enough to use in forks as well as shocks. Fox have changed their recommendations accordingly and replaced green with red in their recent oil charts.

    Thanks for the reply.

    I ended up calling Fox and the guy on the phone told me the green oil is discontinued, that red should work fine in the lower legs.

    I guess the newer forks use the gold oil in the damper and lower legs.

  9. #9
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    Quote Originally Posted by Tillers_Rule View Post
    Thanks for the reply.

    I ended up calling Fox and the guy on the phone told me the green oil is discontinued, that red should work fine in the lower legs.

    I guess the newer forks use the gold oil in the damper and lower legs.
    Gold is too thick for the damper. It is only used in the lower legs when the damper oil is contained (i.e. FIT or CTD).

    The new red replaces the green. The old red (if by chance you found some old stock) won't work well to replace the green.
    Owner of www.shockcraft.co.nz and NZ Manitou Agent.
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  10. #10
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    I have to change the Fox Red 10wt oil into my Fox CTD Performance shock. The Fox Red is a re-branded version of the Silkolene RSF Pro 10wt but i was wondering if would be possible to use a Rock Shox 15wt instead of the Fox Red.

    Fox\Silkolene: 47,36 cst@40C - 303 viscosity
    Rock Shox: 42,80 cst@40C - 245 viscosity

    someone told me that the rock shox oil would not be ok because the lower viscosity implies problems with shock's behavior at low temperatures (0C). is it true?

  11. #11
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    Quote Originally Posted by matteof93 View Post
    I have to change the Fox Red 10wt oil into my Fox CTD Performance shock. The Fox Red is a re-branded version of the Silkolene RSF Pro 10wt but i was wondering if would be possible to use a Rock Shox 15wt instead of the Fox Red.

    Fox\Silkolene: 47,36 cst@40C - 303 viscosity
    Rock Shox: 42,80 cst@40C - 245 viscosity

    someone told me that the rock shox oil would not be ok because the lower viscosity implies problems with shock's behavior at low temperatures (0C). is it true?
    If that's correct then it's suitable. But how did you confirm the viscosity of the rs oil?
    Owner of www.shockcraft.co.nz and NZ Manitou Agent.
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  12. #12
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    Quote Originally Posted by Dougal View Post
    If that's correct then it's suitable. But how did you confirm the viscosity of the rs oil?
    well, according to this data http://www.peterverdone.com/wiki/ima...osity-Data.gif the rock shox 15wt should be a torco rff 20...that is similar to the silkolene rsf pro 15wt (rebranded by fox and sold as fox red 10wt).

  13. #13
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    Quote Originally Posted by matteof93 View Post
    well, according to this data http://www.peterverdone.com/wiki/ima...osity-Data.gif the rock shox 15wt should be a torco rff 20...that is similar to the silkolene rsf pro 15wt (rebranded by fox and sold as fox red 10wt).
    I think rockshox are using maxima now. There are errors in that sheet and I don't rely on anything I can't verify.

    Even official spec sheets have typos and other errors.
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  14. #14
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    Quote Originally Posted by Dougal View Post
    I think rockshox are using maxima now. There are errors in that sheet and I don't rely on anything I can't verify.

    Even official spec sheets have typos and other errors.
    You're right, that sheet is probably outdated.

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