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Thread: Fork oil

  1. #1
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    Fork oil

    Looking to go to a lighter weight to increase small bump sensitivity. Anyone experimented and was their any noticeable difference?

  2. #2
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    I've never messed with that but keep in mind that some dampers require a certain viscosity and type of oil to function correctly. I'm thinking you might be better off just servicing your lowers more often and making sure your seals stay lubricated by doing things like putting the bike upside down for a few minutes before every ride (recently saw a Fox video where Jordy suggested this).

  3. #3
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    What fork do you have? I'm no suspension guru, but this seems like a dubious idea with modern sealed cartridge dampers. Also, isn't small-bump sensitivity mostly determined by the size of the airspring's neg chamber and seal friction? Might want to just take dfinn's advice, buy some stanchion lube, and maybe look into Vorsprung's Luftkappe (or a Debonair spring for pre-Debonair RS forks, they're cheap).

  4. #4
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    I feel like stiction has more of an effect on the small bump sensitivity than damping. The original manual for my fork calls for that thick red liquid o-ring in a lot of places, where the newer ones say to use slick honey. Going to slick honey on the air shaft piston, and making sure to get it really well packed into the lower bushings made a huge improvement in how my fork feels, to the point where I actually had to go up in air pressure.

    Doing a lower service slightly more frequently is probably going to do more for you that an oil viscosity reduction. And remember that lower viscosity will shift that force-velocity curve down across the board and in both directions. Depending on the adjustments your fork has, you may not be able to make up for it with, say, more low speed compression.

    But, if you have a 3-way shock and have rebound and high speed compression all the way soft you could try like a blend of weights to go down a touch. My fork has pretty inadequate compression damping across the board, especially at low speed, and I've actually thought about going up a touch in viscosity. Dropping in a better compression damper would be the better solution though.

  5. #5
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    A little bit of this stuff goes a long says in helping keep things smooth off the top

    http://www.finishlineusa.com/product...ion-fluoro-oil

  6. #6
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    Wouldn't the lower viscosity would speed up all aspects of the fork rather than target any particular speed/position? Might make sense if you're very light yourself and the spring rate in your fork is below the damper's ideal range. Otherwise I'd look elsewhere (as suggested above) to make it more active off the top.

    What fork? Any chance you have a tunable shim stack in there?

    Or go coil.

  7. #7
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    Maxima Plush comes in small increments of weight and can be used in Fit dampers to move the range of your adjustments.
    a positive attitude will not solve all of your problems, but it may annoy enough people to make it worth the effort

    Formerly Rludes025

  8. #8
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    Yes, I do this frequently, as have thousands of people for years. It's definitely a thing.

    I'm changing oil weight in a rear shock as we speak to go the other way.

    As far as embettering top end squish, make sure it's damping that's causing what you're trying to change.

    What fork is it?
    Last edited by kidwoo; 09-11-2019 at 09:27 PM.
    Besides the comet that killed the dinosaurs nothing has destroyed a species faster than entitled white people.-ajp

  9. #9
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    Old fork. 2012 fox float 150mm. Have wanted to replace but don't see many options on 26" wheels out there, so messing around to see if I can tune it a bit.

    I went down on the viscosity last night, and will report back. It isn't old oil. I change it too frequently if anything.

  10. #10
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    The small bump sensitivity of those old Fox suck because of the negative spring design. I tried everything back then to get them better but moving to a Pike was the answer. Recent Fox forks improved that initial stroke.

  11. #11
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    Quote Originally Posted by Canada1 View Post
    Old fork. 2012 fox float 150mm. Have wanted to replace but don't see many options on 26" wheels out there, so messing around to see if I can tune it a bit.

    I went down on the viscosity last night, and will report back. It isn't old oil. I change it too frequently if anything.

    You talking damper oil or just the lube stuff in the lowers?
    Besides the comet that killed the dinosaurs nothing has destroyed a species faster than entitled white people.-ajp

  12. #12
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    Could also be worn bushings causing things to bind.

  13. #13
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    Quote Originally Posted by kidwoo View Post
    You talking damper oil or just the lube stuff in the lowers?
    It's all the same stuff in old open-bath forks. At least that's how it was in the 2011 Float 150 I used to have and serviced a number of times. IIRC, 30 cc of 10 wt in the spring side, 160 cc of 10 wt in the damper side.

  14. #14
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    Quote Originally Posted by simple View Post
    The small bump sensitivity of those old Fox suck because of the negative spring design. I tried everything back then to get them better but moving to a Pike was the answer. Recent Fox forks improved that initial stroke.
    Not sure how recent "recent" is, but I had an '18 Fox 34 that just SUCKED on small bumps. Terrible.

    I solved the issue with an MRP Ribbon coil.

  15. #15
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    Quote Originally Posted by skaredshtles View Post
    Not sure how recent "recent" is, but I had an '18 Fox 34 that just SUCKED on small bumps. Terrible.

    I solved the issue with an MRP Ribbon coil.
    I've been happy with my '18 34. Maybe you got a dud?
    Remind me. We'll send him a red cap and a Speedo.

  16. #16
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    Quote Originally Posted by bagtagley View Post
    I've been happy with my '18 34. Maybe you got a dud?
    Perhaps. Fortunately(?) for me it *also* had a CSU creak/clunk that required warranty of the entire fork... at which point I immediately sold it.

    It never worked worth a shit on small, high-speed hits. I was always arm-pumped at the bottom of one particular local trail, which was irritating, because I never had the issue with the previous fork (an old clapped-out Revelation).

    Kinda glad it sucked, though - otherwise I probably wouldn't have discovered the wonderful, buttery plushness of MRP's coil fork.

  17. #17
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    Quote Originally Posted by Dantheman View Post
    It's all the same stuff in old open-bath forks. At least that's how it was in the 2011 Float 150 I used to have and serviced a number of times. IIRC, 30 cc of 10 wt in the spring side, 160 cc of 10 wt in the damper side.
    Unless they did some weird one off oem stuff, Fox has never made an open bath damper that I've seen. You know that cartridge thing in the damper side? That's where the damper fluid lives.
    Notice all those volumes say "oil bath"
    https://www.ridefox.com/fox17/help.php?m=bike&id=530

    What you guys are talking about is stanchion lube, not damper fluid. Open bath is like the old ghetto stuff marzocchi used to use where the damper uses the same stuff that lubes the lowers.

    As far as changing the weight of that...knock yourself out. It's a little counterintuitive but sometimes going to heavier weight oil lubes better because it's got better adhesion and doesn't just run off as easily.

    As mentioned already I think the negative springs in 2012 might have been when they were still using little coils instead of a negative air spring. Those work okay for a very specific rider weight/fork pressure but go outside of it and it's not so good. Plus the old air springs used to bind. And the first few generations of using negative air springs sucked too. Basically everything air from fox used to suck back then
    Besides the comet that killed the dinosaurs nothing has destroyed a species faster than entitled white people.-ajp

  18. #18
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    Quote Originally Posted by kidwoo View Post
    Unless they did some weird one off oem stuff, Fox has never made an open bath damper that I've seen. You know that cartridge thing in the damper side? That's where the damper fluid lives.
    Notice all those volumes say "oil bath"
    https://www.ridefox.com/fox17/help.php?m=bike&id=530
    When I used to service that fork, which I'm pretty sure has the same internals as C1's fork, you'd slide the lowers off a bit, drain the oil, then pull the lowers completely. Then you'd stick a 1.5 mm hex into the bottom of the damper cartridge to lift the rubber seal at the bottom, then cycle it a few times to purge all the oil out of the damper. Then you'd do the seals, put it all back together with new oil, then cycle the fork a few times to refill the damper with oil. The damper definitely wasn't a sealed unit like a FIT, etc., which IIUC is why it required a whopping 160 cc of oil in the damper leg.

    Also, tons of forks in that list say "O/B R damper". What else would "O/B" mean other than open bath?

  19. #19
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    Quote Originally Posted by kidwoo View Post
    Unless they did some weird one off oem stuff, Fox has never made an open bath damper that I've seen. You know that cartridge thing in the damper side? That's where the damper fluid lives.
    Notice all those volumes say "oil bath"
    https://www.ridefox.com/fox17/help.php?m=bike&id=530

    What you guys are talking about is stanchion lube, not damper fluid. Open bath is like the old ghetto stuff marzocchi used to use where the damper uses the same stuff that lubes the lowers.

    As far as changing the weight of that...knock yourself out. It's a little counterintuitive but sometimes going to heavier weight oil lubes better because it's got better adhesion and doesn't just run off as easily.

    As mentioned already I think the negative springs in 2012 might have been when they were still using little coils instead of a negative air spring. Those work okay for a very specific rider weight/fork pressure but go outside of it and it's not so good. Plus the old air springs used to bind. And the first few generations of using negative air springs sucked too. Basically everything air from fox used to suck back then
    fox float rlc was open bath, if remembering correctly they specced a green fluid for the damper side and red in the air spring with reg splash oil in lowers on air side

    fox stopped offering the green fluid a few years ago and changed their chart at that time as well, swapping the red in for green, which fox says will work, my experience using other closed damper fluids in open bath designs is less than impressive though ive never used fox red this way

    i rebuilt one of these for a friend a few years ago and sourced some open bath damper in 10wt from maxima that worked well enough

    these forks were pretty on/off feeling so idk if oil weight will change a whole lot other than make it under damped

  20. #20
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    People buy forks with lockouts?

    That would explain it. I've owned probably a dozen+ fox forks since they've existed but I damn sure never had one with one of the lockout or rebound only dampers
    Last edited by kidwoo; 09-12-2019 at 03:29 PM.
    Besides the comet that killed the dinosaurs nothing has destroyed a species faster than entitled white people.-ajp

  21. #21
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    Quote Originally Posted by kidwoo View Post
    People buy forks with lockouts?

  22. #22
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    Quote Originally Posted by kidwoo View Post
    People buy forks with lockouts?
    Came with the bike. Didn't know any better at the time.

  23. #23
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    Don't feel bad, I didn't know like half of fox's lineup had marzocchi dampers. Definitely the half that qualifies as "forks I would never have reason to come in contact with" but still......
    Besides the comet that killed the dinosaurs nothing has destroyed a species faster than entitled white people.-ajp

  24. #24
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    Quote Originally Posted by kidwoo View Post
    ... I didn't know like half of fox's lineup had marzocchi dampers.
    Quote Originally Posted by XXX-er View Post
    the situation strikes me as WAY too much drama at this point

  25. #25
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    One ride in and I think it helped. Maybe psychological, but time will tell.

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