WTB fork oil

Discussion in 'Technical' started by Hoghead, Dec 29, 2011.

  1. Hoghead

    Hoghead Ol'Timer

    Part of my Versys fork re-valving project entails a bit of specialized oil design, and I need some very specific oils:

    RockShock 5W medium
    Torco RFF 7
    Golden Spectro 85/150 very light
    Maxima fork oil 5
    Maxima racing fork oil 5

    or best of all:
    Motul shock oil 2.5/20
    Redline synthetic and I will blend my own

    Has anyone seen where to buy these?
    Note that this is Motul Shock oil, and not fork oil which is readily available.

    For those with a technical bent, the issue is Kinematic viscosity expressed in cSt (centistokes units), which is a more accurate way of measuring viscosity compared to "W" units. Quite simply put, it is the relationship between the viscosity and the density of a fluid. The classic example is that honey is more viscous (thicker) than mayonnaise in a stir test, while it pours more easily (the kinematic test). This is the difference between Newtonian and non-Newtonian fluids, and has strained my failing memory.
    Complicating all this is that the "W" rating is not consistent between manufacturers and one needs to use cSt to make an effective comparison.

    The factors I am looking for is the right viscosity (around 16) expressed in cSt at 40C, combined with a high viscosity index (VI) or resistance to thinning out at high temperatures

    For example a Motul fork oil "very light" 2.5 has a viscosity of cSt of 16.0 at 40C and a VI of 100. Given our high ambient temperatures I would like to see a higher VI
    Motul shock oil 2.5/20 has a cSt of 16.1 so almost the same, but the VI is 400

    Redline synthetic oils typically have VI in the very high 300's or 400.

    In our climate, motorcycle forks will run in the +/- 40C temp range, rear shocks will run in the +/-75C range and for those lucky enough to have a rear reservoir, it will be around +/-53C. My experience is with road bikes, so not sure if this is applicable to a motocross bike where the suspension is working a lot harder.
    As you may will imagine at these temperatures, motorcycle rear shocks require a VI of over 300, while the fork does not.

    Perhaps what I am looking for is overkill for a fork, but if it is available in Thailand then that is what I want - if not then perhaps a VI of 150 or above will suffice.

    If it is worth doing, it is worth overdoing
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