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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.
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  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.
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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.
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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 (0°C). 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 (0°C). is it true?
    If that's correct then it's suitable. But how did you confirm the viscosity of the rs oil?
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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.

  15. #15
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    I don't want to open new thread so i will ask here.
    I want to service my fox fork on my MTB Cube LTD SL 2016. The fork is Fox 32 Float FIT4 with code - CYFY, 100mm travel. I can't find clear information how much oil to use in each fork leg. I have this new 20w gold fox oil. Can you provide me with information how much oil to use ?

  16. #16
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    Quote Originally Posted by BraneMKD View Post
    Fox 32 Float FIT4 with code - CYFY
    Use that code here: https://www.ridefox.com/help.php?m=bike

    You'll find a bath oil volume chart somewhere in the results.

  17. #17
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    Ty PhilipJ. https://www.ridefox.com/help.php?m=bike&id=649
    From this link i guess my fork is
    All 32/34mm 80-120 FLOAT NA2 Air-Side Bath 25cc
    All 32/34mm FIT4 Damper-Side Bath 15cc

    so many things to get confused with.

  18. #18
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    If you want to try riding clean, FWIW I've been making up the Red 10wt's 47 cSt viscosity by blending 2 parts WPL Shockboost 10wt to 1 part WPL 20 wt. Resulting blend has a VI of about 220, which has been fine in my Fox DHX shocks, no fade issues for me, and the old shocks run so smooth now. I'm about to do a Fox fork damper with it as well.

    I've been using the WPL 20wt for semi-bath in Fox forks for awhile now with great results, and replaced Float Fluid (90wt gear oil) with WPL's ForkBoost, which doubles as an excellent stanchion lube/cleaner.

    The WPL oils are naturally very lubricious, unlike the usual oils which need additives (that wear out) to get slippery. They also smell a lot better and clean up a lot easier.

    Disclaimer: I'm not connected with the company, just like their stuff.




    Quote Originally Posted by Patuman View Post
    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!

  19. #19
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    Quote Originally Posted by DawnVoyager View Post
    If you want to try riding clean, FWIW I've been making up the Red 10wt's 47 cSt viscosity by blending 2 parts WPL Shockboost 10wt to 1 part WPL 20 wt. Resulting blend has a VI of about 220, which has been fine in my Fox DHX shocks, no fade issues for me, and the old shocks run so smooth now. I'm about to do a Fox fork damper with it as well.

    I've been using the WPL 20wt for semi-bath in Fox forks for awhile now with great results, and replaced Float Fluid (90wt gear oil) with WPL's ForkBoost, which doubles as an excellent stanchion lube/cleaner.

    The WPL oils are naturally very lubricious, unlike the usual oils which need additives (that wear out) to get slippery. They also smell a lot better and clean up a lot easier.

    Disclaimer: I'm not connected with the company, just like their stuff.
    If you measured the oil from your Fox DHX you'd see it's not 47 cSt. I have not found 47cSt oil in any factory filled Fox. Only 32 cSt and the newer 15 cSt.

    The straight WPL 10cSt would have been a good match for stock. Is it riding harsher and needing rebound more open now?
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  20. #20
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    Quote Originally Posted by Dougal View Post
    If you measured the oil from your Fox DHX you'd see it's not 47 cSt. I have not found 47cSt oil in any factory filled Fox. Only 32 cSt and the newer 15 cSt.

    The straight WPL 10cSt would have been a good match for stock. Is it riding harsher and needing rebound more open now?
    Hah! Excellent information, Dougal. I have 3 old DHX-airs-- will try straight WPL 10w (35 cSt, not 10 cSt) in one of them and look for the difference. 47.4 was the best info I could find from the closely-guarded secrets, but clearly out of date. I was surprised to see a recommendation for a damper oil that thick too. It's a little slower on rebound, but not as much as I'd think it should be if the correct viscosity is 15.

    Maybe they feel great because of the change from the standard mix of mud and foam that was in these dampers when I got them, and the regressive geometry of the bike it's on-- a little stiffness is good. My 3rd DHX is filled with the official red 10wt-- unfortunately with a Corset but will get the air cans identical and try to compare next week. That's a big spread in viscosity-- presumably the internals have changed for the thinner oils? These shocks are all 2007-2008.

    Out of interest, what method do you use to measure kinematic viscosity?

    <EDIT> Should clarify: I said "unfortunately with a Corset" just because it makes comparison difficult-- the Vorsprung Corset improves the old DHX-air so much it might as well be a different shock.
    Last edited by DawnVoyager; 03-06-2018 at 02:33 AM. Reason: Clarification

  21. #21
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    Quote Originally Posted by DawnVoyager View Post
    Hah! Excellent information, Dougal. I have 3 old DHX-airs-- will try straight WPL 10w (35 cSt, not 10 cSt) in one of them and look for the difference. 47.4 was the best info I could find from the closely-guarded secrets, but clearly out of date. I was surprised to see a recommendation for a damper oil that thick too. It's a little slower on rebound, but not as much as I'd think it should be if the correct viscosity is 15.

    Maybe they feel great because of the change from the standard mix of mud and foam that was in these dampers when I got them, and the regressive geometry of the bike it's on-- a little stiffness is good. My 3rd DHX is filled with the official red 10wt-- unfortunately with a Corset but will get the air cans identical and try to compare next week. That's a big spread in viscosity-- presumably the internals have changed for the thinner oils? These shocks are all 2007-2008.

    Out of interest, what method do you use to measure kinematic viscosity?
    The newest stuff is allegedly switching to 15cSt in rear shocks now, they switched in the fork FIT dampers a few years ago. Thinnest I've run in a Fox rear shock damper to date is 22 cSt and that works great. I'll try thinner at some stage.

    I have no idea why Fox was publicizing 47 cSt red and green while filling fork and shock dampers with 32cSt (presumably Torco). There are several downsides and no real upside to more viscosity in a shim stack damper. I can sort of understand it in an open-bath fork. But that's it and other, thinner, oils could still lubricate well enough.

    I built my own oil test rig. I can vary temp from 0-40C. It's been amazingly useful in sorting out the minefield of fork and shock oils and has measured to date 372 samples. It also brings in other questions.
    Like did RS choose their 0w30 oil because it matched Fox green at 47 cSt? Why is the Fox R3 5wt the worst performing oil I've found in the cold?
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  22. #22
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    Quote Originally Posted by Dougal View Post
    The newest stuff is allegedly switching to 15cSt in rear shocks now, they switched in the fork FIT dampers a few years ago. Thinnest I've run in a Fox rear shock damper to date is 22 cSt and that works great. I'll try thinner at some stage.

    I have no idea why Fox was publicizing 47 cSt red and green while filling fork and shock dampers with 32cSt (presumably Torco). There are several downsides and no real upside to more viscosity in a shim stack damper. I can sort of understand it in an open-bath fork. But that's it and other, thinner, oils could still lubricate well enough.

    I built my own oil test rig. I can vary temp from 0-40C. It's been amazingly useful in sorting out the minefield of fork and shock oils and has measured to date 372 samples. It also brings in other questions.
    Like did RS choose their 0w30 oil because it matched Fox green at 47 cSt? Why is the Fox R3 5wt the worst performing oil I've found in the cold?
    Have you measured the oil out of a 2017 shock? It’s red in colour and seems thicker in viscosity, as I occasionally do relative tests on oils by draining them out of a particular syringe and timing it. Was noticeably thicker than 32cSt oils.

    I have found an old fox service manual with ISO 32 oil being recommended but will probably never understand why the aftermarket reds oil these days is different to the clearly different to the factory orange. Maybe Torco is cheaper but why not sell that AM?

  23. #23
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    Quote Originally Posted by JohnnyC7 View Post
    Have you measured the oil out of a 2017 shock? It’s red in colour and seems thicker in viscosity, as I occasionally do relative tests on oils by draining them out of a particular syringe and timing it. Was noticeably thicker than 32cSt oils.

    I have found an old fox service manual with ISO 32 oil being recommended but will probably never understand why the aftermarket reds oil these days is different to the clearly different to the factory orange. Maybe Torco is cheaper but why not sell that AM?
    I don't think we have. But I'll keep an eye out and make sure to test the oil when we do.

    Torco also comes in whatever colour you want. Torco RSF Med in the Torco bottle is red. Fox Torco is/was more orange, X-fusion give the exact Torco spec and have a yellow oil that measures identical to both of them.

    I guess when you buy enough you can ask for whatever colour dye you want!
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    Quote Originally Posted by Dougal View Post
    If you measured the oil from your Fox DHX you'd see it's not 47 cSt. I have not found 47cSt oil in any factory filled Fox. Only 32 cSt and the newer 15 cSt.

    The straight WPL 10cSt would have been a good match for stock. Is it riding harsher and needing rebound more open now?
    I don't have a viscosity measurement apparatus, but in the interests of science I just ran 2 nearly identical stock shocks with different oils sequentially on the same bike. Both were set to the same pressures (150 boost; 165 main), which gave 25% sag. Both were recently serviced with fresh oil and bleed.

    1. Fox DHX-air 4.0 with stock Fox Red 10w oil of unknown viscosity. Stock seals.
    2. Fox DHX-air 4.0 with WPL blend to 47 cSt viscosity. Enduro air seals.
    Question about Fox fork red/green oil-imgp9969_v1.jpg
    Findings:
    #1 and #2 are indistinguishable from each other. Wouldn't describe either as harsh, and both had rebound control beginning to slow at 8-10 clicks in, strongly noticeable at 12 clicks, and rebound at max (21 clicks) averaged 1 second. Both of these are "custom tuned" by Fox for the bike, an RM Slayer.

    Conclusions:
    Either I'm a Philistine unable to distinguish suspension performance (possible, though the rebound measures are close to quantitative), or these shocks care less than claimed about viscosity, or the two shocks are secretly just different enough from each other inside to offset the oil differences, or my favourite theory: the viscosity of the two oils is similar.

    Since I can't tell the difference and like both, guess I'll keep using the easier to work with WPL.

  25. #25
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    Interesting test. Your next challenge (should you choose to accept it) is to run straight WPL 10wt (35cSt) at your next service and see if you notice the difference.

    With shim stack dampers oil viscosity isn't a problem until it gets too high and starts creating extra damping in ports where you don't want it. I can't recall offhand if the DHX4 had any particularly tight ports that would become noticable. I bought a DHX5 air about 5 years back with the intent of tuning it up for Mrs Dougal. But on dissassembly found there was nothing worth tuning inside!

    The rebound needle is the place viscosity is most apparent (speeding up when hot, slowing down when cold etc). But the DHX5 instead of a needle ran a threaded plug that wound up and down over a port in the shaft. Not giving the fine control most needles do.

    Has your top DHX ever been serviced? It was easy for a while to see what had been serviced by the Fox guys in NZ. They used green 10wt in everything.
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  26. #26
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    Question about Fox fork red/green oil

    Quote Originally Posted by DawnVoyager View Post
    I don't have a viscosity measurement apparatus, but in the interests of science I just ran 2 nearly identical stock shocks with different oils sequentially on the same bike. Both were set to the same pressures (150 boost; 165 main), which gave 25% sag. Both were recently serviced with fresh oil and bleed.

    1. Fox DHX-air 4.0 with stock Fox Red 10w oil of unknown viscosity. Stock seals.
    2. Fox DHX-air 4.0 with WPL blend to 47 cSt viscosity. Enduro air seals.
    Click image for larger version. 

Name:	IMGP9969_v1.jpg 
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    Findings:
    #1 and #2 are indistinguishable from each other. Wouldn't describe either as harsh, and both had rebound control beginning to slow at 8-10 clicks in, strongly noticeable at 12 clicks, and rebound at max (21 clicks) averaged 1 second. Both of these are "custom tuned" by Fox for the bike, an RM Slayer.

    Conclusions:
    Either I'm a Philistine unable to distinguish suspension performance (possible, though the rebound measures are close to quantitative), or these shocks care less than claimed about viscosity, or the two shocks are secretly just different enough from each other inside to offset the oil differences, or my favourite theory: the viscosity of the two oils is similar.

    Since I can't tell the difference and like both, guess I'll keep using the easier to work with WPL.
    Philistine! You better not go using that kind of language on Pinkbike, it will confuse them.


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    Fascinating details. The top DHX (rightmost below) was given a "full service" about 12 hours of use ago by a local suspension shop when the Fox oil was put in. This shop is particular about viscosity index for shocks since they do a lot of bike park business, so I assume they used whatever incarnation of Red 10w is current. Will get more details.

    In other news, I went back in time and accepted your challenge a couple days ago, but wasn't happy with the results for an interesting reason: My third shock is a recently-serviced DHX5 and contains straight WPL 10w at 35 cSt. On this test, it is stiffer than the other two shocks-- still not harsh, but noticeable. Also, to maintain 25% sag the pressure had to be dropped from 165 to 155 psi. The rebound begins a couple clicks further in, but surprisingly at full closed (19 vs. 21 clicks) takes a full 4 seconds, even with the lighter oil. I concluded the DHX5 is too different from the DHX4 for oil comparison.

    I haven't had the rebound apart on a DHX4, so don't know how/if it differs from the 5, but my guess is this DHX5 at the very least has a different tune from the other two (stiffer shims). Not sure though how the same size air can could require lower pressure for the same sag-- it's not seal friction because they're new just like the ones in the other two shocks, and without air the movement feels the same as the other two. Frankly I think after a check of the Propedal spring, this DHX5 is a candidate to try a 22 or even lower viscosity oil. Name:  IMGP9970_v1.JPG
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  28. #28
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    Is the whole difference between the 4 and 5 supposed to be the volume adjuster? I see your 4's got the lockout switch too. There's a big difference in performance with the boost valve shocks simply by opening the boost valves to "reset" the internal pressure in them. Then of course running equal reservoir pressure.

    I have run 22cSt in a Float R with no adverse effects. I was looking for better cold temp performance and I found it, but have since found even better fluids for the cold and better suspension for everywhere.

    If anyone is chasing high VI fluids at 47 cSt (I wouldn't bother, but hey some might) then Spectro allegedly do a Golden fluid with VI of 370 but I haven't been able to verify. Fox green was VI 256 and Silkolen RSF10 VI 303. Motorex 10wt (2016+) is 49.5cSt and VI 252.
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    Difference is supposed to be the "Bottom Out Adjuster" (to make the available space for air above the IFP in the reservoir chamber smaller), and the dial adjust for the Propedal valve tension instead of the on/off lever. And neither of those can be characterized as a "lockout"; more like a slight stiffener, but it's enough. I prefer the lever anyway, though there's an argument for using it to fine tune the balance in the shock between the various parameters. How do you mean "opening the boost valves"? Cracking the bleeders? I haven't heard of this idea.

  30. #30
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    Quote Originally Posted by DawnVoyager View Post
    Difference is supposed to be the "Bottom Out Adjuster" (to make the available space for air above the IFP in the reservoir chamber smaller), and the dial adjust for the Propedal valve tension instead of the on/off lever. And neither of those can be characterized as a "lockout"; more like a slight stiffener, but it's enough. I prefer the lever anyway, though there's an argument for using it to fine tune the balance in the shock between the various parameters. How do you mean "opening the boost valves"? Cracking the bleeders? I haven't heard of this idea.
    The boost valve is the same as the SPV valves Manitou and Progressive used in the mid 00's. It relies on a bubble of trapped air as a pressure to work against. Over time the air pressure inside can either increase or reduce depending on what's going on and leaking out vs oil leaking in.

    To reset it simply open it up, clean, grease and reassemble. It's at the base (top) of the piggy back reservoir.

    The DHX5 dial preloads a spring against that same valve to adjust compression a little. I think the lever on your DHX4 does the same, just on/off.
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    Quote Originally Posted by Dougal View Post
    Is the whole difference between the 4 and 5 supposed to be the volume adjuster? I see your 4's got the lockout switch too. There's a big difference in performance with the boost valve shocks simply by opening the boost valves to "reset" the internal pressure in them. Then of course running equal reservoir pressure.

    I have run 22cSt in a Float R with no adverse effects. I was looking for better cold temp performance and I found it, but have since found even better fluids for the cold and better suspension for everywhere.

    If anyone is chasing high VI fluids at 47 cSt (I wouldn't bother, but hey some might) then Spectro allegedly do a Golden fluid with VI of 370 but I haven't been able to verify. Fox green was VI 256 and Silkolen RSF10 VI 303. Motorex 10wt (2016+) is 49.5cSt and VI 252.
    In the US, Redline is widely available and a group VI ester based oils with extremely high VI.


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    I guess the usual expectation for unusually high VI synthetic oils is they get that way from VI enhancing polymer additives that wear out comparatively quickly under the mechanical shear of getting squirted thru ports and shims and return you to lower VI. This compared to oils that don't depend on additives and have less spectacular VI to start, but but keep that VI stably over longer use. I think that's the story for the biolubricants like WPL-- they say their 35, 25, and 17 cSt oils have stable VI's of 250, 280, and 320 respectively, which brings us back to the other advantage of thinner oils-- better VI where it matters-- for hardworking dampers.

  33. #33
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    Quote Originally Posted by Cary View Post
    In the US, Redline is widely available and a group VI ester based oils with extremely high VI.


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    They do, but they've got a big gap between 32cSt (438VI) and 69 cSt (275VI).

    Quote Originally Posted by DawnVoyager View Post
    I guess the usual expectation for unusually high VI synthetic oils is they get that way from VI enhancing polymer additives that wear out comparatively quickly under the mechanical shear of getting squirted thru ports and shims and return you to lower VI. This compared to oils that don't depend on additives and have less spectacular VI to start, but but keep that VI stably over longer use. I think that's the story for the biolubricants like WPL-- they say their 35, 25, and 17 cSt oils have stable VI's of 250, 280, and 320 respectively, which brings us back to the other advantage of thinner oils-- better VI where it matters-- for hardworking dampers.
    That's the interesting thing. I've yet to measure a significant viscosity change in shock oil. Even when it's come out black like old tractor oil.

    I have had 20 year old oil samples in the bottle thicken up to a multiple of their original viscosity. I suspect something evaporated out over that time.

    My feeling is that anything over mid 300 for a bike application is just wankery. I've had significant change going from 200VI to 400VI oils in my rear shock. Previous issue was rebound speed increasing as the shock got hot (~60C) and then slowing again as it cooled down on less intense sections of the same track. Higher VI fixed that to the point it's not noticable. But this is a shock with less than 30cc of oil on board. Normally when you hit temperature issues you go straight to a bigger and heavier shock.

    It's also worth noting that VI is calculated from points 40C to 100C and the path from one to the other could be quite different for different fluids. 0-60C is the temp range that matters to me.
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    Nerd Alert

    Well, that was fun. Just skimmed this:

    https://www.stle.org/images/pdf/STLE...cle_Sept11.pdf

    From the article, sounds like evaporation of the petroleum base stock from the oil-additive mix (and escape through imperfect seals/lids) explains some of the often significant volume losses in oil over time, especially semi-bath oils, and also the thickening of your 20 year old samples. As the lightest base molecules escape, effective VI-additive proportion and also proportion of the heavier oil fraction increases, thickening the mix. Wonder if this is where getting stanchion seals that are nice and slick but too loose to slow the loss of oil vapors and keep dirt out spells shorter life for coatings and bushings?

    In the opposite direction, shear damage over time to a hard working oil, particularly something in a sealed damper where base can't easily escape, reduces the VI. It's important to recall that VI improvers don't change the room temperature viscosity of oils much; their job is to offset the thinning of the base stock that naturally happens at higher temps. Maybe if you tested some old black shock oil you'd find similar viscosity to original at room temp, but lower viscosity at 60C than for the fresh oil. Or possibly the black stuff (oxidized oil and maybe aluminum oxides if the oil's gone fizzy) could offset this somehow. What is the VI of mud slurry and overcooked oils?

    According to the article, one thing you can do to formulate a higher quality VI improver is control the molecular size of the additive so it's both relatively small, and also very uniform. Cheaper additives work great because they have some really big molecules, and bigger molecules thicken up like porridge better with high temperature, but unfortunately the big molecules also get chopped up by shear stress more easily. Higher concentrations of uniform medium size molecules are more durable, but also more expensive because they're harder to make.

    Question remains how those incredible (and probably as you point out, useless to cyclists) VI=438 oils are made. It's got to be some combination of bigger (weaker) molecules, higher additive concentration (possibly impairing slipperiness), and the golden hope: new miracle additive chemistries.

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    A confirmation at 47 cSt for the Red 10w

    Got confirmation from the very tech-oriented shop that rebuilt (with Fox 10w Red) one of my shocks, that 47 cSt at 40C is correct for this oil. They also said that in their experience, DHX-air shock performance isn't very sensitive to damper oil viscosity, so getting the viscosity exactly right isn't that critical at least in this case-- slight changes to low speed rebound and compression; that's all.

    They're also in accord with Dougal that a bit lower VI is unlikely to be noticed much unless you're doing long, steep, repeated descents.

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    Quote Originally Posted by DawnVoyager View Post

    Question remains how those incredible (and probably as you point out, useless to cyclists) VI=438 oils are made. It's got to be some combination of bigger (weaker) molecules, higher additive concentration (possibly impairing slipperiness), and the golden hope: new miracle additive chemistries.
    Keep in mind that higher quality base stocks (i.e. PAO and Esters) have naturally higher VIs and therefor need less in the way of VI improvers. I believe WPL claims no VI improvers in their oils. Both redline and WPL use Group V Ester based fluids, but they are from different sources, Redline being petroleum, WPL plant based.



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  37. #37
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    Quote Originally Posted by DawnVoyager View Post
    Got confirmation from the very tech-oriented shop that rebuilt (with Fox 10w Red) one of my shocks, that 47 cSt at 40C is correct for this oil. They also said that in their experience, DHX-air shock performance isn't very sensitive to damper oil viscosity, so getting the viscosity exactly right isn't that critical at least in this case-- slight changes to low speed rebound and compression; that's all.

    They're also in accord with Dougal that a bit lower VI is unlikely to be noticed much unless you're doing long, steep, repeated descents.
    It's very clear that Fox were selling and recommending 47 cSt oil for service. The mystery is why theywere shipping out forks and shocks with completely different oil?

    Even the unmolested X2's I've had in for service had 32 cSt oil inside.

    One guy told me they use 47cSt oil for US assembled forks and shocks. That may well be true, but all the forks and shocks I see are built in Taiwan, not the USA.
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