Fork Oil Weight change... Whats it do..?

Discussion in 'Australia' started by GoneAgain, Jul 28, 2014.

  1. GoneAgain

    GoneAgain Huh?

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    ok... it's time to change my fork oil..... :evil

    been googling.... probably shouldnt have, as it raised more questions than it answered.... :rofl

    anyway.. question:

    if all things stay the same (springs, air gap, fork oil brand etc), what will i notice, feel/performance wise and the front end, if i :

    1) use a higher oil weight (eg increase from 7.5 to 10)
    2) use a lighter oil weight (eg drop from 7.5 to 5)

    ??

    thanks again.. :clap



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    #1
  2. D_A

    D_A Long timer

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    Heavier oil will increase the effective damping, in other words the forks will move up and down a little slower and feel stiffer.
    Lighter weight oil will do the opposite, allowing the forks to move up and down faster and feel softer.
    The former seems to be more popular for people wanting to push the bike harder and/or ride on rough terrain, the latter for those who like a plusher ride but don't push hard or ride rough trails. Light oil soaks up little bumps better but heavy oil is better for big knocks and helps prevent the forks from topping and bottoming out.
    Personal preference plays a big part with fork oil choice. Personally I stick to the stock weight but I also ride slower on dirt than your average nine year old, and then only on nice graded dirt roads. ymmv
    #2
  3. Muruk59

    Muruk59 Adventurer

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    I believe going to a heavier grade oil will make things a lot firmer on the compression side of the suspension and the recovery of the compressed fork a slower.
    Opposite for lighter weight oils. You can go lighter or heavier depending on your own requirements and needs but only in degrees, I certainly would think twice about doubling or halving the weight of oils used.
    Cheers
    Greg
    #3
  4. vagueout

    vagueout Long timer

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    Pretty straight forward answer. Thicker oil will slow down the rebound/increase the damping, thinner oil the opposite. How that translates to front end feel for the rider is if too heavy an oil/slow rebound, the fork springs will be too slow to return to normal and start to feel "heavy" and jolt over the road surface as well as lose traction very easily. Too light an oil/decreased damping will make the front end very floaty and light trending to wobbly. On dirt surfaces lighter oil/less damping can be a good move. It wont cost much to experiment with different oils and with due diligence improve your bike for the purpose you use it.:*sip*
    #4
  5. Tenerrod

    Tenerrod Make it shiny

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    I'm putting 15wt in my stock tenere forks this week, up from 10wt.
    I wouldn't double the oil wt straight out until you experience how they go with a smaller increase.
    Really depends on what riding you plan to do.
    I'm upping mine because l ride faster than my ability on roughish ground on what is considered a fairly soft oem suspension.
    In an extreme case too heavy an oil will prevent the forks from completely rebounding and they could eventually compress to the stops. Extreme case in rough conditions that is so don't let me put the wind up you, just saying.
    Have lots of rags on hand, it's a messy job :D
    #5
  6. Dr AT

    Dr AT Long timer

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    It'll trick you into thinking you have stiffer sspension when what you really have is slower suspension. Unless you're bouncing around like a pogo stick, fix spring rate first, then oil height, then only adjust oil viscosity if you are really sure dampening is the issue. Too much dampening will reduce traction :deal
    #6
  7. neilaction

    neilaction Slightly Less Adventurous

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    [​IMG]
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  8. PBee

    PBee ...---...

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    Curry last night Neil?
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  9. neilaction

    neilaction Slightly Less Adventurous

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    :lol3 No.
    But some Guinness on the weekend. :evil
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  10. Tenerrod

    Tenerrod Make it shiny

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    Oils aint Oils

    Here we go again.

    Yes what Doc said.
    I just cant afford springs and yes l'm bouncing around......
    #10
  11. Lupine128

    Lupine128 That's MR Band Aid!

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    the down side to just running heavier weight (thicker) oil is that it is more prone to cavitation/aeration. used to be known as foaming.
    if you force a thicker oil through the same size hole (or stack) it will slow down the rebound damping, it will also stiffen the compression damping.
    it can also cause problems if you ride corrugations, rougher fire trail, any thing that will give prolonged, constant movement to the forks. the oil will cavitate (get full of bubbles), and you will lose both rebound and compression damping.
    it's the reason that you change you spring rate and stack ratios when you want to change the performance of a cheaper fork.
    the idea when you tune suspension is to run the thinnest oil you can to achieve what you want.

    what is the bike?
    and how hard do realistically ride it?

    i'd hate to see you throw a heavier oil in it, ride down the plenty and end up with a spring on a stick for a shock...
    #11
  12. craig525

    craig525 Ktm nut

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    I have always run lighter weight oil and a little less on all my KTM AND DR
    #12
  13. GoneAgain

    GoneAgain Huh?

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    the bike is an F800GS... and she got aftermarket springs and cartidges in her 20,000kms ago (hence oil change time..)

    To be fair, i'm not the fastest rider in the world...but i'll take her pretty much anywhere..

    i find the front wanders a little on sandy/gravelly corrogations...

    other than that, i'm pretty happy... the kit came with Maxima 7wt fluid...so thats what went in...

    just trying to work out if thats what 'i' should have in there or go a bit heavier or lighter...

    (and yep, i understand one brands 7 is another brands 5 and another brands 15 etc........ so i'll be staying same brand...)

    thanks so far... :freaky



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  14. barneyrubble

    barneyrubble ?

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    :nod
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  15. Uncle Crumpet

    Uncle Crumpet Long timer

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    Heavier oil as it's heavier will increase the unsprung weight of your front end, lighter oil as it's lighter will decrease it! If you want the front end to feel really "planted" try vegetable oil.
    #15
  16. neilaction

    neilaction Slightly Less Adventurous

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    :lol3
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  17. charlie59

    charlie59 Been here awhile

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    we have a winner.:clap
    #17
  18. fayeslane

    fayeslane Rankest of amateurs

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    And if you ride like me, try baby oil :lol3
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  19. Angry Pete

    Angry Pete Yeah, whatever

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    What happens if he uses "Extra Virgin" oil?
    #19
  20. fayeslane

    fayeslane Rankest of amateurs

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    He scores a pillion :lol3
    #20