Formula Tech Trials Forks

Discussion in 'Trials' started by motobene, Mar 14, 2018.

  1. motobene

    motobene Motoing for 46 years

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    Time to change the fork oil on the 2017 Sherco Factory. My bike has the 39mm diameter aluminum-stanchion rod Formula Tech forks.

    This thread includes specs for the steel-stanchion rod forks. Steel is stiffer, so the inside diameter of the stanchion rods is bigger on the steel forks. The fork spring is larger in diameter on that fork, and there is a little more internal volume, affecting the bled and collapsed oil height spec.

    I read Formula's PDF oil change docs. One is for the right fork (cartridge/rebound side), and the other is for the left fork (spring/compression side). The documents specified volumes & heights for the steel-stanchion forks:

    Right-Cartridge-Rebound ~250cc, then adjust by bled & collapsed oil height in the tube = 55mm. Splat Shop UK says the spec for the aluminum-stanchion fork is 75mm.

    Left-Spring-Compression ~250cc, then adjust to bled & collapsed oil height in the tube = 130mm (5.12").

    The Formula documents call for 5-weight fork oil, which isn't an accurate spec. Splat Shop UK says the oil used by Formula is 3.47 centistokes (cSt) at 100 degrees C and 15.02 centistokes at 40 degrees C (which is about as hot as forks ever get). Viscosity Index (VI) is reported to be 106.

    The above converts to 41.6 Saybolt Universal Seconds (SUS) at 100 degrees C and 78.3 Saybolt Universal Seconds at 40 degrees C.

    Splat Shop says the closest oil they have found to this is the all synthetic ipone 3 weight fork oil:

    By the way, a handy viscosity converter is here, last line in their conversion table.

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

    Maxima's Racing fork oil in 5 weight is 85-150 SUS, which is thicker (but I found that to be correct).

    Please read farther down for specific results and helpful info from other riders.
    #1
  2. heffergm

    heffergm Long timer

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    I haven't. The fronts on both my bikes feel about the same. Same Tech forks, one has had the oil changed umpteen times with Motul 5w, the others are brand new.
    #2
  3. heffergm

    heffergm Long timer

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    By the way, the Splat Shop specs are air gaps.
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  4. mung

    mung Been here awhile

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    12 Raga has the same fork. I use 10 wt Maxima in both fork legs at 20 mm less air gap than what is called for. Comp. side clicker is middle of the range and rebound is 5 clicks out from stock. For my 250 pounds of mediocre intermediate skills they work great. Plush on the little stuff,never bottom on drops and stays up in the travel. When I bought bike no stiffer springs were available so I went this route and they work better than any other forks I have tried.
    #4
  5. lineaway

    lineaway Long timer

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    So, did you get the special tool or weld up your own?
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  6. heffergm

    heffergm Long timer

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  7. heffergm

    heffergm Long timer

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    Special tool for what?
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  8. lineaway

    lineaway Long timer

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    Some of the fiork caps, depending on model.
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  9. heffergm

    heffergm Long timer

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    Don't need one for the tech's. It's just a 17mm box end (or 15, i can't remember...)
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  10. lineaway

    lineaway Long timer

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    Yes snd no. The sqare end can spin inside, still needing a tool.
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  11. heffergm

    heffergm Long timer

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    Huh? I've changed the oil in the Tech's a dozen times and I can't think of what you're referring to.

    These are the caps on the Techs. You can't do anything other than unscrew them with a box end wrench.

    Once they're unscrewed from the stanchion, you just need another 17mm (or 15mm... again, memory fails me) wrench on the damping side to hold the locknut that keeps the damping rod connected to the cap.

    Attached Files:

    #11
  12. lineaway

    lineaway Long timer

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    I sgree the one you have in the pic works that way. A guy with a new scorpa asked me about his the other day. The square piece moved independantly fro the out side with the holes. Beta forks have a special tool too.
    #12
  13. heffergm

    heffergm Long timer

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    I've never had a set of techs that looked other than the ones I posted. Weird.
    Are you sure they weren't Marzocchi's on the Scorpa. Those definitely have the setup you're talking about. You can use the special tool, or you can hack your way through getting the caps off with a hose clamp...

    2018 Scorpa seems to have Marzocchi's: https://birkettmotosport.com/scorpa/scorpa-2018-twenty
    #13
  14. laser17

    laser17 Long timer

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    I remember Stu saying something about a difference between cheaper steel and high end Al Tech's with the external dual damping adj. Could that explain the disassembly differences? My guess is that Heffergm bikes have all had the high-end Techs - but that's just a guess. I'd also be willing to wager that line knows his Zokes from Techs. Didn't Sherco buy up all the old Marzoochi inventory at auction, so the switch back to Zokes while they last.
    #14
  15. heffergm

    heffergm Long timer

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    I've had bikes with both steel and aluminum Tech's, and I can't recall there being a difference in the cap (but its been a while since I had that bike). My current bikes are both aluminum, one of the standard variety and the other with the extra compression adjustment. The caps are the same.
    #15
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  16. heffergm

    heffergm Long timer

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    #16
  17. 2whlrcr

    2whlrcr gooligan

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    My TRS Raga looks to have the same forks.
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  18. motobene

    motobene Motoing for 46 years

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    'Air gap' is a way to think about the secondary spring.

    Fork oil level bled and collapsed is a common description. I suppose someone could get confused. It's just the distance between the open end of the stanchion tube and the oil, and it's only a reference number.

    The larger numbers for the aluminum-stanchion forks are because of the reduced volume from the thicker aluminum tubes. In other words, the lower oil level in with aluminum stanchions provides roughly the same secondary spring as the higher oil level in the steel-stanchion forks.

    This spec indirectly represents an 'air gap', as the inserting of caps and spring, change the volume or 'gap', as does fork extension.

    The oil level spec determines the amount of extension force that results during forks compression from the trapped air volume being compressed. The trapped air is a secondary, supplemental spring to the metal spring. We don't screw the caps on with forks compressed to not Rob from the secondary spring.

    I plumed an air pressure gage into a fork cap once. It was fun to watch the pressure spike way up when landing the bike hard.
    #18
  19. motobene

    motobene Motoing for 46 years

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    Sounds like simple 5 weight would be cool, especially with the warm season coming up.

    I was concerned only because the forks work so well. I didn't want to slow them down noticeably.
    #19
  20. the toe cutter

    the toe cutter Adventurer

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    I messaged the Tech rep on Facebook and he told me that Kayaba 01 Motorcross fork oil is the exact same as the OJ01 fork oil the manual recommends (at least on my '17 gas gas 250). I ordered it through Cycle Gear (Tucker Rocky) and forks feel great.

    This may help others who are servicing the forks and need a walk through guide with pics.
    http://www.rideformula.com/products/moto-forks/trial-39-standard/
    #20
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