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I have a SR Suntour Rux S 130 mm fork and I don't know what pressure should I put into the left valve.

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For some reason I think this fork should have only 0 - 15 PSI pressure, but I don't know what source I have this from. Where can I go to learn the correct pressure for my fork?

UPDATE as per the current answer:

In the owner's manual linked in the current answer two facts are stated. First is the pressure sheet which seems to regard any fork listed in the manual (my fork included):

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Second is the table with forks specifically, which takes things to a dramatic change:

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Am I to understand that normally, as per the first chart, the pressure should be around 110 PSI, but for my fork, it should be 15 PSI?

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The manual posted refers to Air forks AND Coil forks. As for this page:

http://www.srsuntour-cycling.com/index.php?screen=sh.detail&tnid=135

your fork is Coil Spring / Hydraulic Open Bath with Air Pressure preload adjuster.

The table present at the page 3 of the mentioned manual refers specifically to Travel-Adjustment-equipped suspensions, which doesn't seem to be your case. Anyway, the pressure recommended for the Air Preload system, in this table, ranges from 15 PSI to 43 PSI (27 psi for your weight, as I understood from your question).

The table at page 6 of the manual refers to adjusting the SAG (how much the fork sinks under rider's weight while in normal riding position) via air pressure, suggesting an initial value of 15 PSI, but implying that rider's preference should determine the ideal setting.

These forks which mix open bath, coil spring and air-pressure preload adjustment on the same side of the fork (I have a similar one, a 2004 Marzocchi Drop-Off- II, which I run with 0 PSI otherwise it is too stiff for my taste) tend to need relatively small pressures, since the pressure is only a fine-tuning. That is different from a air-only-spring, where you need a much higher pressure since it is air alone that conteracts rider's weight and bumps.

At last, it is interesting to know the ideal pressure RANGE (10 PSI is much different than 110...), but once this is determine, trial and error and experimentation is the definitive way to know what's the ideal pressure for you.

Hope that helps.

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  • So basically what you're saying is that I can safely ride the fork on 0 PSI if it never reaches it maximum drop?
    – Frantisek
    Commented May 10, 2012 at 22:13
  • Basically, yes. These spring+air forks rely mostly on the coil to do the hard work, the air is then mostly a way to fine-tune the riding characteristics according to your weight, riding style and personal preference. Bottoming-out and hard-as-a-rock are obviously wrong, extreme tunings, but anything in between can be considered "safe" or "right" if that's how you like it.
    – heltonbiker
    Commented May 11, 2012 at 14:03
  • Also, for sime time I was running my mentioned fork with negative pressures (compressing it with the schraeder valves pressed, so the air would come out), but eventually I removed the spring from one side and now I have a much wider tuning range via air pressure (in case you wonder, Marzocchi themselves suggested me to do so, via mail). Of course, each fork is different, but the principles should be the same. Casually, mine and yours are 130mm all-mountain forks.
    – heltonbiker
    Commented May 11, 2012 at 14:05
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It looks like this is the owner's manual for your fork which has a chart on page 3. Please, however, make sure this is the correct guide for your fork. I am not familiar with this brand, so I cannot be certain, but it looks right.

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  • Updated my question.
    – Frantisek
    Commented May 10, 2012 at 19:37

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