Viewing 29 posts - 1 through 29 (of 29 total)
  • Can I mix 5wt and 20wt suspension oil to get 15wt?
  • Elfinsafety
    Free Member

    Cos all the local motorbike shop had left was 20wt. Already got some 5wt, so I thought I could mix the two to get a 15wt or thereabouts.

    The 15wt would be for lubrication in my Rebas, as I only used 5wt and that’s not right really.

    Is there a sort of formula type thing for doing this?

    Please not too technical as I am an idiot and if it gets too compulcated I will become upset and run away. 🙁

    davidtaylforth
    Free Member

    Sling it in and mix it up, add some water to thin it out even more.

    CaptainFlashheart
    Free Member

    I only use Extra Virgin myself.

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    Elfinsafety
    Free Member

    See I might be an idiot, but that’s just rude. ^

    If you’ve got nothing helpful to say then please don’t say anything.

    I only use Extra Virgin myself.

    That’s cos you are one. One of these days, you might find a lady willing to show you what things are all about.

    I only said ‘might’…

    CaptainFlashheart
    Free Member

    If you’ve got nothing helpful to say then please don’t say anything.

    Sound advice…..

    TandemJeremy
    Free Member

    if its only for the lubrication bit not the bit in the damper then viscosity is not too critical Its not as obvious as it seems the mix ratios apparently

    So just mix a bit of the 5 with a more of the 20 and I am sure it will be fine

    uplink
    Free Member

    Yeah but no

    It won’t be exact but near enough for most – I would have thought

    momo
    Full Member

    Yes you can, and if my maths is correct 1 part 5wt to 2 parts 20wt should give you 15wt.

    Elfinsafety
    Free Member

    See? TJ, Uplink and Momo can be helpful. Why can’t you?

    It’s cos you don’t know nuffink. Silly billy. 🙄

    Elfinsafety
    Free Member

    Does anyone have a very simple equation or owt or this?

    something a bit simpler than this:

    😯

    Like, WTF?

    RealMan
    Free Member

    That thing above is very simple, it’s basically saying

    a = b + (a – b)

    As for the oil I’ve got no idea, unless you have a way of measuring it and just use trial and error.

    retro83
    Free Member

    http://www.widman.biz/English/Calculators/Mixtures.html

    you need to know the viscosity in cst. I’d just bung in a third of the 5wt and hope for the best. One manufacturers 15wt can be really different from anothers anyway.

    Burls72
    Free Member

    That thing above is very simple, it’s basically saying

    a = b + (a – b)

    As for the oil I’ve got no idea, unless you have a way of measuring it and just use trial and error.

    Smart ass 😉

    anto164
    Free Member

    surely, mixing different weight oils won’t work..

    Call me stupid, but wouldn’t the two different weight oils just sit on top of each other, and not mix well?

    Unless you got them to magically mix together properly?

    kimbers
    Full Member

    yes you can mix them together fine

    the marzocchi manual even recommends this iirc

    TuckerUK
    Free Member

    If you want an accurate answer you can discard using wt or weight (neither of which are a internationality recognised measurement), and must instead use centistokes. Wt/weight are so meaningless you can actually get one manufactures 5 wt which is twice as thick as another manufacturers 10wt!

    Then, after having determined the viscosity in centistokes at a given temperature you can use the free program by Shell Oils called Bunker Calc available somewhere online.

    Some fork oils have their viscosity in centistokes listed here.

    Elfinsafety
    Free Member

    So, as Momo suggests, a 2:1 ratio of 20 to 5 then? TBH, I imagine it only needs something very slightly thinner than 20wt as it’s for lubrication, not damping.

    Ok i’ll give it a go. Thanks for the info.

    Feel fee to argue endlessly about fluid dynamics or whatever stuff I haven’t got the faintest idea about and just glaze over when I read it. 🙂 No point in missing the opportunity for a good argue now, is there?

    avdave2
    Full Member

    as I only used 5wt and that’s not right really.

    Peter Poddy in one of his posts about servicing Rebas says he’s a pair that have been going for 4 years just using 5wt oil for the lubrication.

    Elfinsafety
    Free Member

    Well that’s as maybe, and Poddy knows his stuff (although I don’t remember him saying that), but I’ve noticed increasing stiction not long after servicing, and was wondering if this was a symptom of using lubricating oil that was too ‘light’. Hence, I want to try something closer to what RockShox recommend.

    Poddy told me that owt can be used really for the lubrication, indeed his excellent Poddyguide sez to use 15wt for this purpose.

    Still quite new to suspension servicing, so thought I’d try using the proper recommended stuffs, see if it improves things at all. Trial and error and all that, fun to learn things.

    molgrips
    Free Member

    Doesnt’ really matter if it is for damping anyway.

    Most forks ime have enormous ranges of adjustments in their er.. adjusters.. so if the oil’s too thick just tweak the knobs.

    scruff
    Free Member

    I’ve got Automatic Gearbox fluid in my Lyrics just to see, can tell any difference.

    epicyclo
    Full Member

    Back in the days when I used to fiddle around with motorbike suspension I used to regularly mix oils to get the result I wanted, so go for it.

    You don’t have to get too technical.

    If you want a measurement, then get an old funnel, mark a level on it, and put a restriction in the bottom (I used to use an old carburettor main jet).

    Fill to level with fluid. Time how long it takes to dribble through.
    Fill with mixture and repeat.

    Use the time ratios as an indication.

    So long as you do this in a place where there is no great temperature variation, it will be a reasonable guide.

    scottidog
    Free Member

    Mixing oil is fine. I do it often as my Fox and Marz forks use 7.5w fluid which my local motorcycle garage doesn’t stock, so I mix 3 parts 5w with 1 part 15w to get 7.5w.

    I’m not smart enough to figure out the proportions you need to mix 5w and 20w to get 15 though I’m afraid!

    I_Ache
    Free Member

    Just put the 20wt in it doesn’t matter. As long as you have some lubricating oil in it will be fine. Having said that the 5wt that you have in at the moment is a bit too light as you say but 20 wt will be fine. Its not like its damping oil so it wont mess up the charicteristics of the fork.

    toys19
    Free Member

    The above is correct ie 1/3 5wt to 2/3rds 20wt.

    Mixing fork oil is best estimated by the rule of mixtures
    Fractionofa+fractionofb=C

    so if you mix equal quantities of 2.5 and 7.5 oil its
    (0.5 x 2.5) + (0.5 x 7.5) = (1.25 + 3.75)=5

    Or to make 25 from 13.6 and 26.7
    Mix 13% of 13.6 and 87% of the 26.7

    Which is (0.13×13.6)+(0.87×26.7) =1.768+23.229=24.997

    I wouldn’t be too worried mixing one type of oil with another, its just long chain polymers really, viscocisty is related to average chain length.

    This has been detailed and argued over in this thread and this one

    Needless to say I am right .

    neninja
    Free Member

    As Tucker said above the wt can be very misleading. One brands 5wt can have the same properties as another brands 15wt.

    Use the cst figure instead. I recently bought some 10wt oil with the exact same cst as Fox suspension oil (Fox use rebranded Torco oil – I suspect the supplier I got it from also rebrand Torco oil). The best bit was that it cost £6.00 for a litre instead of Fox suspension oil costing £15+

    toys19
    Free Member

    neninja, what brand was this as I need some 10wt fox oil?

    neninja
    Free Member

    It was Smith and Allen in Darlington who are an oil distributor and blender. I asked them for all specs for their own 10wt suspension oil and it was an exact match for Fox Green 10wt.

    PeterPoddy
    Free Member

    Just put the 20wt in it doesn’t matter. As long as you have some lubricating oil in it will be fine.

    Yes. This!

    I use Fox Float fluid in all my RS forks which is considerably thicker than 15wt, and I’ve also used 5wt as well. It matters not a jot. 🙂

Viewing 29 posts - 1 through 29 (of 29 total)

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