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Undertanding nitrogen pressure, why the differences in PSI?

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So I have been setting my shocks up with 150 psi of Nitrogen pressure based recommendations I have gotten here.  I have used that pressure in Showa 44 and 50mm, PDS shocks, Kayaba 46s, and so far all have been great. All the bikes are trail bikes, ridden off road and the terrain mostly technical. rider weights have varied from 150-275lbs on 250 and 450 sized bikes. So after looking at recommendations on race tech and in the manuals the recommended PSI are 165, 168, 175 etc.. depending on what manual your reading from or website you are on..

So my question is: can someone please enlighten as to what is a good N2o pressure and for what type of riding. etc. Also, when someone might want to run more pressure rather than less and what the outcomes/effects would be? more or less pressure for bladders vs. pistons or does it matter? guessing that more psi is going to give a bit more rebound and or bottoming resistance or more/ less initial plushness/small bump absorbtion?

thanks for the thoughts..

Edited by dnsducks

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Higher pressure prevents cavitation , but creates more friction on the shaft seal , higher pressure does give more spring effect and rebound will be affected when the shock heats up , but the change from 145 to 165 is not huge

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4 hours ago, CaptainKnobby said:

The less you use helps the shock ride lower in the stroke. I weigh 165lbs and race MX and on my 2015 YZ250 I use 145 psi. And the same on my 2016 YZ450F.

A few PSI in the shock either way is going to have a negligible effect on ride height.  The spring holds the bike up.  The bladder pressure is solely intended to control cavitation.

I suspect the pressure may vary based on shock body diameter and shaft size.  The larger diameter shocks run at lower internal pressures and may not need as much bladder pressure to control cavitation.

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Pressure is needed directly based on compression shim stacks , you have a huge wad of shims, your going to need more pressure to cope, I think bladder and sizes will play a role as well as the previous post says.

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That makes good sense. I will continue to run the 150psi pressure then with confidence. For the off road duty I/we do and corresponding light(er) compression stacks, 150 seems to work well and allow for a bit more plushness on the initial part of the stroke according to my butt Dyno. Although I haven't really experimented much back to back. I might start. Just to see if I can tell any difference. Thanks!

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I used to run 200psi in my old '83 KX125, I never really understood suspension back then, but it made the compression stroke feel more 'controlled' without feeling too harsh. Hard to describe really...like you could feel it moving through the stroke a bit slower when hitting big stuff, like stiffer high speed I guess.

I only tried it as the guys that did the shock didn't know what the recommended pressure was, so they put 200 in and said I could let some out if I had to lol.

This was 25 odd years ago....

The change in spring rate is directly related to shaft size and how far into the shock it is. Displacement if you remember science classes.

Edited by DEATH_INC.
because....

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