5wt or 10wt fork oil?

Discussion in 'Land of the Rising Sun: ADV Bikes from Japan' started by whittrated03, Dec 10, 2011.

  1. whittrated03

    whittrated03 Steady Rollin' Man

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    I am close to servicing the front forks on my k4 DL650. Does changing fork oil weight improve performance? I've read somewhere that 5wt fork oil helps quite a bit. Any info is appreciated..
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  2. PeterW

    PeterW Long timer

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    There's no good answer. It depends on the riders weight and riding style as well.

    Generally, less brake dive, heavier oil.

    Less harsh, lighter oil.

    Given it's a K4 though, just changing the oil may make a huge difference anyway, it'll probably be the consistency of water, look (and smell) like something small and rodent like died in there by now.

    If you want it 'right' pick up a small hand transfer pump from an auto-accessory store. Start with 5 weight, go for a ride, too much dive, pull half it out, replace with 10 wt. (Repeat until it feels good).

    But - as above, I doubt you'll need to obsess about it. It should be 'better' with either.

    Pete
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  3. whittrated03

    whittrated03 Steady Rollin' Man

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    I read in a previous thread that there is a 7.5wt fork oil...
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  4. AustinJake

    AustinJake DR650 - Versys

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    Weights vary radically, Castrol 10w is less vis than Maxima 5w. I started with Maxima 5w because Maxima's numbers make linear sense overall. I discovered I wanted something thinner so I had to switch to BelRay, currently running the 2.5w (9.2 cSt@40C, the second lowest viscosity fluid made)

    This is a chart I boiled down from 3 different suspension fluid spreadsheets. The Maxima and BelRay are readily available and their numbers make the most sense. RedLine is the choice if you end up wanting the thinnest fluid. I like BelRay now because I can mix different weights and get anything between 9.2 and 37.4 cSt@40C.
    [​IMG]

    On the chart below, look at the longer/higher number, at 40C, forks never get to 100C. Start with an oil near 15 cSt@40C (centistokes) like the Maxima 5w. If that is too thin, go to the Maxima 10w.

    [​IMG]
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  5. X-Ray

    X-Ray Over Radiated

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    I just replaced my fork springs with Wilbers and they recommend 7.5wt fork oil. Purchased mine from the Beemershop in California. Cost around $150. Huge difference and worth the money. I didn't want to continually dick around with fork oil height and weight and their system did the trick. Used the turkey baster method of gauging oil height but Motion Pro makes a tool that I would use next time.
    #5
  6. AustinJake

    AustinJake DR650 - Versys

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    Which 7.5w fluid did you use?

    PJ1 Fork Tuner 7.5w = 27.5 cSt@40C
    Agip Fork 7.5 = 31 cSt@40C
    White Power 7.5 = 33.4 cSt@40C
    Silkolene ProRSF = 37.0 cSt@40C



    Most cartridge type forks use a viscosity of 16 cSt@40C.
    Most damper rod type forks are specd for a viscosity of 34 cSt@40C. Basically ATF Fluid) although most setups require far thicker for adequate performance.
    http://www.peterverdone.com/wiki/index.php?title=Suspension_Fluid
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  7. X-Ray

    X-Ray Over Radiated

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    I used the Wilbers 7.5wt.
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  8. Chuck in Indiana

    Chuck in Indiana Been here awhile

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    I just changed the suspension on my '09 Wee. In the forks, I went with Gold Tech Emulators, the .90 spring and the recommended ATF fluid. In the shock, it was a rebuild by Sasquatch in Boise.

    The result is a solid, firm ride. I'm looking forward to it next year when I get the bike fully loaded and out on the road.
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  9. AceRider01

    AceRider01 Fully Loaded

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    while everyones experience and preference may differ and you would get different opinions, talking about what weight oil one uses without
    1) naming the brand/range of oil is useless - as people pointed out viscosity rating varies from manufacturer to manufacturer - no relevancy unless we can get the Cst@40c rating;

    2) not knowing the weight of rider is useless - people who weights 70kg or less will often find the stock (k7 onwards especially) quite good and dont understand what the fuss is about.

    3) preference in riding style and type of roads on is also important for someone trying to use the information as a starting point.

    4) rate of spring and what other suspension mod has been done to the bike is also useful.


    to the OP, the answer depends on your weight; whether you run stock spring or not, what type of riding you do and what brand of oil you plan to use.

    FYI, i am 94kg, use 0.90kg spring in one leg and 0.95kg spring in other- runs silkolene pro rsf 2.5 wt which has a around 14cst@40c rating and i use intiminator. My rear shock is elka unit with a 9.4kg spring. I ride a lot of bumpy broken asphalt road and my preference is a little more towards compliance, even though i consider myself a sporty rider. 95% of my riding is on tar, the rest easy forest road.
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  10. X-Ray

    X-Ray Over Radiated

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    Ace, I absolutely agree with you.

    When I was doing the research into upgrading my 09 DL650, by the time I was done my head was spinning. I'm not a motorcycle mechanic guru nor do I have any friends who are. I spent hours reading threads on ADV, Stromtrooper, and watching OnTheThrottle's suspension tuning videos and came to the conclusion that suspension tuning was definitely a science and an art. People are messing with different weight oils, adding intiminators or cartridge emulators and sometimes drilling holes into them, cutting spacers, raising the forks in the clamps, etc. etc. etc. I wanted a tested solution to the three problems the bike has: 1. front-end dive, 2. loading up the back of the bike and running out of adjustment on the rear shock, and 3. overall a more compliant ride like the nicer more expensive bikes have. I wanted to tear the bike apart once to install everything, not spend weekend after weekend tweeking.

    After speaking with Ted Porter at the Beemershop, I chose the Wilbers solution - front fork springs and oil and a rear shock with remote pre-load adjuster. Wilbers has actually designed and tested the solution on the bike. Ted took my measurements, my riding style, and how I load the bike. This information goes to Wilbers in Germany when they build the rear shock and helps to decide which front fork spring to use. I thought this was a better solution, for me, than guessing on the front fork components and having the rear shock rebuilt. I still plan on taking the bike into a local shop to have everything measured and tuned with me and my luggage on the bike.

    For the money and the time it took me to install, I am very pleased with the outcome as it solved the three issues I had with the bike.
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  11. Kawidad

    Kawidad Long timer

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    Go over to the strom sites and read away. :deal

    Generally it's thought a heavier oil, between 10w and 15w will give better dampening characteristics to the wee strom forks. The wee forks respond well to a heavier spring with a heavier oil. To my mind if you are on the road, stay 10w or so. If you're off road a lot, then go up to a 15w.

    On my 650 wee I did the heavier springs from Sonic, which worked really well. I then used the 15w oil, but thought it was a little too heavy. However, it did work really well off road. I always thought 12.5w, splitting the difference would be the hot ticket. :D
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  12. Tseta

    Tseta Lost

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    AustinJake & AceRider: What about the viscosity index (VI) of the oil?

    -T
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  13. AceRider01

    AceRider01 Fully Loaded

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    My understanding is it gives an indication of how stable the viscosity characteristics is over a large temp range. A high vi is preferable.. But this is less critical in forks compare to say shock oil when temp can get very high. I chose silkolene pro rsf because it has q very high VI and it is priced reasonably cheap here.
    #13
  14. AustinJake

    AustinJake DR650 - Versys

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    Agree with AceRider01, here's a quote from the pvdwiki:
    While motorcycle rear shocks require very high VIs (over 300) to function well over such a huge temperature range, motorcycle forks and bicycles do not. Anything over 100VI will be serviceable for them.

    I chose BelRay for my forks because it will give me the greatest range to adjust the vis by mixing different weights.
    #14
  15. Kawidad

    Kawidad Long timer

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    That's all good info, but aren't you guys over thinking it?

    I mean the wee strom uses a dampening rod type fork that was designed sometime like 150 years ago. It's not like it's a modern MX cartridge fork. :deal



    Just say'n..........:augie
    #15
  16. Dolly Sod

    Dolly Sod I want to do right, but not right now

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    You'll bet the best results if you install racetech cartridge emulators right before you fill the forks with new oil.
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  17. Chuck in Indiana

    Chuck in Indiana Been here awhile

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    It's a bit more involved than just installing the emulators but it can be done by someone with reasonable technical skills and the necessary tools.

    Unfortunately, making these improvements on the front end of the bike highlights the deficicies at the other end and something would need to be done there also.
    #17
  18. Dolly Sod

    Dolly Sod I want to do right, but not right now

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    Actually I didn't find the rear nearly as bad as the front. I rode with emulators up front and the stock shock in the back for a couple of years. I think the rear benefits greatly from a stiffer spring and a rework from Sasquatch, but is reasonable in stock form. Whereas the front is just mushy and harsh in stock form.
    #18
  19. ianbh

    ianbh Been here awhile

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    AustinJake,
    Am I correct in assuming you changed springs and tossed the damping rods?
    If so could you tell us:
    Spring rate and brand
    Emulators, intimators (sp), ??
    and if it's not too personal, your weight and if you travel one or two up.

    TIA Ian, Iowa
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  20. AceRider01

    AceRider01 Fully Loaded

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    emulator and intiminator still required damper rod to function. In essence they bypass the function of damper when it comes to compression damping and uses their own mechanism to control compression damping with added function of providing a "bleed" to soften the compression damping when encounter a larger size bumps. Rebound damping is still controlled by the damper rod as always.

    If you dont travel on roads with a lot of bumps, and you dont want to bother to tune them, intiminator or emulator is not necessary. Even damper rod is old -tech, it works reasonably well when tuned to the rider's weight and preference in 90% of the situation.

    Installing emulator or intiminator on vstrom is not hard. If you have change a set of brake pads and bleeded the brake before, you have all the necessary skills. It does sound scary the first time you do it, after that you wonder why you even worried. Just read the numerous articles on how to on the net and in this forum and it's handy to have the work-shop manual too

    What it is potentially time consuming and often frustrating until the end is tuning the intiminator or emulator to your own liking. Unfortunately both manufacturers invent a good little tool to minimise the design shortcoming of damper rod but neglect to do any testing on vstrom (and most bikes) specifically to provide useful setting guidelines. If you go with intiminator or emulator, there are various threads where people has done some extensive testing and theories behind the different settings so as to shorten your tuning time.
    #20