Nitrogen Pressure adjustments?

sirhk100

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What incriments should I change the pressure in my shocks at? I mean if I bump it up 10PSI will I notice a difference? 25psi? etc...?

Thanks
Khris

'99YZ400, (for sale, $3900)
'92 Ford Exploder lifted work in progress,
lifted golf cart (sold)
 

Kritter

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I had 200 in my SAWs per the instructions and was having a hell of a problem with my tires coming up into the fender wells and ripping the rubber. I bumped them up to 250 for this last weekend in Barstow and it was like night and day. I beat it good and it only rubbed a couple times but thats cuz I hit a berm track and then braked so I didnt kill myself on the opposite berm. If you can take a N2 bottle out to the dez then do it in 25 psi incrments and use the same test sectionHit something you think it should ride fine over and then dial it in until it does. Dont go too high though cuz you can damage the seals.

Kris
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"Jesus loves you, everybody else thinks you're an A-hole"
 

RacerX

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Make sure you add nitrogen when the truck is at full droop. This will give you your accurate reading of 10 or 20 psi or whatever pressure you chose. The nitrogen pressure increases as the shock goes to bump and if you add nitrogen while the truck is a ride height, you wont get a accurate adjustment.
 

JCA

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But you will be able to compare apples to apples out in the dez if it is not at full droop.

J.C. Andrews
Andrews Racing
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1992f150

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Is there a reason to do this insted of just revalving the shocks?
<---confused

Azusa: shame of the foothills
 

Kritter

Krittro Campbell
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Yeah to see if yo can dial it in without re valving

Kris
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Dylan

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You really don’t want to go to low with the shock pressure either. Don’t go below 150PSI as a general rule. The real minimum pressure is dependant on the compression valving and the max shaft speed, the more you have of either of these the more pressure you need to resist cavitation. What your mostly doing when you are adjusting the pressure is allowing more or less cavitation.
Except on really light vehicles the spring rate change due to N2 pressure is negligible unless it’s an emulsion shock.
Ultimately you should only change pressure to identify what kind of change you need to make next time you revalve and then put it back up to 250PSI. Also those seals are good to a lot higher than 250PSI but high pressure does add to seal friction, again negligible except on light vehicles like mountain bikes.
Dylan
 

sirhk100

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Thanks for all the info, I'm running 200PSI all around just as a starting point, figured start early. My front end is doing great. My rear end could use a little more sitffness. I talked to Shane @ Bilstein and he said not to go above 250PSI with the 7100 that I'm running in the rear of my Exploder. He said if I hit that and still am not happy then revalve. JC, are you bringing the tank out to the Dez Sat. night? Nevermind if you say yes here, you know it'll be empty by the end of the night from everyone using it.....

Khris

'99YZ400, (for sale, $3900)
'92 Ford Exploder lifted work in progress,
lifted golf cart (sold)
 

Just4Fun

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I was told to never change the pressure, but to have the shock revalved. Is that wrong???
 

sirhk100

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Shane at Bilstein said that if I needed them stiffer on compression to try bumping up the pressure cause it would help. He said if I hit 250psi not to go higher and that I would have to revalve them. I'm new at this and am trying to get my ride dialed in. BTW I'm running 9100 and bilstein bumps up front and 7100 in the rear and this is on an Exploder.

Khris

'99YZ400, (for sale, $3900)
'92 Ford Exploder lifted work in progress,
lifted golf cart (sold)
 

pciscott

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ON the Protruck we ran up to 300 pounds in the front shocks and never had a problem with the bilstein shock. I say if you are trying to make it stiffer go big and ad 50lb and see if that makes a difference, because 10lb is almost nothing. Another reason I like to see higher pressure is to lessen the amount of cavitation in the shock. When you shove the shaft of the shock in at a high rate of speed this creates an air pocket under the piston. When your suspension goes to droop there is no valving until this pocket disapears. No matter where the reservoir tube is mounted you will get some degree of cavitation, but high shock pressures help reduce it. We also have ran up to 350psi in the air bumps, but we started to bend shafts once in a while so we upped the valving and lowered the pressure to around 250. One time I blew the top off an airbump in the Protruck on a huge hole, the damn thing blew a hole in my hood and sounded like a cannon. The main reason I like a lot of shock pressure is because you can lighten up your spring rate for a softer ride. Then pump up the shocks and they start to work like air springs. If you let the nitrogen out of my Protruck you would lose 2 inches of ride height. The main point I am trying to get across is when you are testing and you want to try something new go big which means 20% because I feel you would not notice much change with 5 or 10%. Good luck and one last thing, make sure the ring clips are seated in the Bilstien reservoirs before you go loading the pressure up high. When they come off they make a huge mess and are dangerous.

God Bless America

Scott Steinberger Trophy Truck #7
 

sirhk100

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Thanks for the info, I was planning on just bumping it all the way up to what the max Bilstien recomended. I know my 9100 up front could hit 300PSI but not too sure about the rear 7100.

Crap, that had to be a surprise when the end cap blew off!!!!! Did it just blow out the Schraeder or did the canister it self explode? Talk about a violent failure!!

Khris

'99YZ400, (for sale, $3900)
'92 Ford Exploder lifted work in progress,
lifted golf cart (sold)
 

Jack

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as far as putting 300 in a 7100, it would be less of a problem then the 9100 because of shaft diamiter it does not displace as much fluid, therefor the air presure does not go up as much.
 

partybarge_pilot

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There are several schools of thought on the shock pressure deal. On the down side of running high pressure is stiction caused by the seal pressing on the shaft. The larger the shaft the more stiction. All new motor cycles come with air bleeds instead of shrader valves. This helps compliance over small bumps while the valving takes care of the bumps. On the cavitation side, when the piston rises in the bore not only does it displace oil but it also creates a vacuum on the back side. Since oil doesn't stretch well this helps suck the oil through the piston. Alot of worries about cavitation are misplaced. You should be more concerned about how your seal pack works under vacuum and if it will get suck up into the shock body. Not helping the fade issue is the boiling piont of oil is greatly reduced under vacuum. Putting the reservoir out the bottom eliminates this.

Now that My head hurts, it's time for a beer! TGIF!
 

Just4Fun

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I went to king today guys to pick up some more coil overs and talked to him about the pressure ?'s you guys asked. He said to leave it at the same pressure that is stamped on the resevoir cap and just revalve them. When you are running a bigger shafted shock, you dont want to be running all that pressure because it is bad for the seals. As for the smaller shocks, its less of a problem since you have a smaller shaft. For you guys that have smaller shafts, im sorry to hear that, thats more of a personal problem, and should be on a different post and questionaire.
P.M. Fabrication
 

sirhk100

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Well I'm just a freak of nature cause I've got big shafts in the front and small shafts in the rear!!!

'99YZ400, (for sale, $3900)
'92 Ford Exploder lifted work in progress,
lifted golf cart (sold)
 

Just4Fun

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Ya, u must be a freak considering u have small shafts in the rear. I on the other hand are like u with a large shaft in the front, but i dont have any shafts in the rear.
P.M. Fabrication
 
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