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No pressure in rear shocks


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Hi all,

I tried to check the pressure in the rear shocks of my SV 1100. When I did, both sides just bled out to 0. The left side was at about 65 lbs. and the right at about 80 lbs. When I put the gauge on the valve it registered pressure but just bled down right away. Maybe my gauge is bad.

I did some searching on the forum but didn't find much so I'm asking, can I use air or do I have to take it somewhere to get nitrogen and how much pressure?

Thanks,

Bruce

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Nitrogen or Argon works but you can put air in and it will work ok for the most part. I don't think that the differance will show up unless you run it real hard in the rough stuff. You can't really check the pressure on a shock without losing all the gas because there is such a little amount in the shock. The oinly way to get it to the right pressure is to set your supply source to the pressure you want and then charge it. I set the pressure on my argon tank I use for tig welding to about 170 pounds and then charge the shocks, being sure to quickly remove the nozzle from the shock to minimize the amount that can escape. When I was doing a lot of shock tuning where I had them off and on a lot, I just used air and then switched to Argon when I was done.

Lenny

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That's basically what I did also, but I used a 130 psi air compressor and set the pressure regulator as high as it would go (about 100psi) and then just help the chuck on the valve for a while so it could push as much in as possible and pulled off real quick.

From what I understand, the nitrogen molecule is much larger than the O2 molecule, so it doesn't react to heat as much, but what we breath is mostly nitrogen 78% & O2 21% any way, I just us air, if I had lots of money riding on the shock performance, like an Indy driver, I'd use nitrogen, but I'm not and I don't.

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Ok what I learned with my air shock set up is that there is a small amount of shock oil in it and the shocks use nitrogen reason being is the nitro stays cooler than the air and if u wanna say more stable. Regular will hear up faster and can lead to moisture with temp changes ! I don't have my own nitro set up yet but what I do have is a gauge that u can fill and release nitro on its made by fox racing and u can also buy it from poly performance online it's 75$ my gauge goes from 0-600 it has a valve on it that u use so u can check nitro then once u r undone u release it then the guage very minimal loss wen used correctly

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Thanks guys. I talked to Casey at JMC Powersports and he didn't recommend using air. He said the gas actually mixes with the oil in the shock and air has a little moisture and will contaminate the oil. Doing some searching about the use of Argon looks like it should work. My neighbor has a Mig welder with Argon but I think it is a mixture with some other gas. I'll check it out. I did find a place in Yuma which is about an hour and a half away who will fill them for $10 a piece if I take them off. That might be the best route.

Bruce

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Found this on oneof teh desert racing sites.

"As a former hydraulics mech on military aircraft, we were taught that nitrogen was used because it was clean and dry and therefor prevented corrosion and enhanced the life of the component. I wouldn't hesitate for a second to use air if I needed to finish a race, after all air is mostly nitrogen anyway. Nitrogen is not somehow immune from the gas law....when it gets hot it tries to expand just like every other gas, therefor you are going to see pressure increases in hot shocks no matter what gas you use. Just like the myth of using nitrogen in your tires, total scam."

What he didn't say is that the moisture in air is what causes the majority of the extra pressure build up. Without the moisture the two gases would be about the same. The gases will build pressure too. If you start out with say a shock that is 75 degrees, and you bring that to 150 degrees, the pressure of the gas will double. So I guess if you filled your shocks on a humid day in Florida you would have more moisture then if you did it in Arizonia when it has very dry air. You could always put a moisture seperator on your compessor. Pressure build isn't going to be an issue unless you get your shocks hot.

There seems to be two view points on this. I agree that nitrogen or argon is best but I will continue to use regular compressor air if I'm going to have my shocks on and off for tuning reasons. I do fill them with argon when I'm done tuning. If I was racing, I would put new oil in and charge with nitrogen (or argon) before a race.

Lenny

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