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Changing springs and oil viscosity, any recomendations guys?

ExTrEmE BiKeRExTrEmE BiKeR Posts: 149
edited August 2010 in MTB workshop & tech
I currently have an 08 domain 302 with stock spring (160-180lbs) and am changing it to a soft spring (140-160lbs) to better suit my weight, which is close to 140lbs with gear. I've been told that changing the oil viscosity in the upper damper leg from the recommended 5 wt to a 2.5wt oil would make the fork compress/rebound faster which is better for light riders. I find that the fork, even with rebound as fast as I can adjust it externally is still too slow for my liking. Is it ok to do this even though rockshox recommends using 5wt oil? I'd also like to know what type of oil you guys are using. Which brands are you guys putting in your fork and why?


  • nicklousenicklouse Posts: 50,675 Lives Here
    yep a lighter oil is suitable for a lighter spring.

    any as long as there are no seal swellers. motorex/Torco etc...
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • Try the new spring first with standard weight oil in them, then change it if feel you need more sensitivity.
    You may save yourself some money :wink:
    Suspension servicing, tuning, parts, setup and race support
  • i've also heard that alot of people use 10w30 synthetic motor oil in the lowers. will that mess up the fork or change how it performs? supposedly the lubrication properties of the oil itself are more important than using the exact viscosity the manufacturer recommends?
  • supersonicsupersonic Posts: 82,708 Lives Here
    If that was the case, then you wouldn't be wanting to change the viscosity ie weight ;-)

    I'd keep with hydraulic fluid for forks.
  • but its only lower oil so it doesnt really make much of a performance difference i think (but may be wrong). motor oils need to withstand more heat and friction than a suspension oil so wouldnt it be better than using suspension specific fluid?
  • supersonicsupersonic Posts: 82,708 Lives Here
    Not if it destroys your bushes and seals.
  • :shock: 10w30 in a fork! Bet they use shampoo, alcohol and sugar for brake fluid too!!
    Will be cheese and cake next!!
    10 weight is the thinest it will be, then when the fork starts working and gets hotter, the oil gets thicker, which is what you want in an engine, not suspension.
    Single grade hydraulic fluid designed for the job everytime. :)
  • 10w30 is 10wt when its at 0 degrees celsius and is the equivalent of 30wt when it reaches temperatures of 100 degrees celsius or over, which it would never reach in a fork. a 5w20 would be better but i guess its still not meant to be used in a fork. what about using fluid meant for motorcycle forks? ... rk_oil.php

    could i use something like that in the upper right leg? it comes in 2.5wt which is what i want
  • supersonicsupersonic Posts: 82,708 Lives Here
    Yes, it what I used to use in my Judies, albeit 7.5wt.

    I thought most oils got thinner when they heat up!
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