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  1. #1
    mtbr member
    Join Date
    Feb 2008

    Oil Weight - Fork Performance????

    How does oil weight affect fork performance (rebound, compression)?
    5wt vs 10wt vs 15wt, etc...

    My fork recommends 15wt, but I plan on experimenting with a couple different weights.

  2. #2
    mtbr member
    Join Date
    Jul 2003

    A few thiings you need to understand.....

    The weight ratings of fork oil are realavent ONLY to the same company. Oil weights are not very standard from brand to brand. One companies 5w may well be another companies 10w. So if you want to experiment, find out what your fork has in it now and stick with that brand of oil to get a good comparison.

    Next, suspension manufacturers set up their forks and shocks to work with a specific weight of oil to give a specific performance and adjustment range to the damping system. Changing the oil weight will affect both the performance and adjustment parameters. So if your fork came with 15w oil in it, a 10w oil will change those ranges. You will have faster (read less) rebound and compression damping force throughout the whole adjustment range. As an example, lets say that your rebound adjustment with 15w brand X is 5 clicks from full open and that it works the way your want it too. To get that same amount of damping with 10w brand X oil you will have to increase that setting. So you would likely have to add a few clicks to get the same amount of damping force with the lighter oil. And you'd have to add even more if you went to a 5w oil. The same applies to compression dampers just in the oposite direction. The lighter oil flows more easily through the damper valves and creates less damping force for a given setting.

    And it should be noted that in going with lighter oils, if you go light enough, you may eventually find an oil weight that will pretty much give you 0 damping. The valves, shims, etc. that make up the damper system are set up for a specific weight oil. In your case the damper is set up to give a specific resistance to oil flow through it with a 15wweight oil. If the oil is enough lighter it will flow through the valves etc. too easily to have any effect. Not likely, but it is possible, especially with systems designed to use heavier weight oils.

    So, basically what you will be doing in going to ligther weight oil is changing the performance curve of your damping system. The lighter oil will give faster rebound and compression speeds throughout the range of adjustment as compared to the heavier stock oil. It's a good "tunning tool" especially for lighter or heavier weight riders. So experiment away. You may well improve the overall performance of your fork in the long run. That and it's fun!

    Good Dirt
    "I do whatever my Rice Cripsies tell me to!"

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