Quick Shock Question

[In_the_works]

Would it be harmful to temporarily charge a reservoir shock with air instead of nitrogen? This isn't for offroad use, just for a few miles on the highway until I can get them charged tomorrow. the shocks are 2.5 Kings.

[kjmiller1]

If somebody smarter than me doesn't answer before you need one, I just drove around without them charged and it didn't seem like it was a problem

[WFODAN]

this question has been gone over about ten times in the last two months , so the answer to your question is yes you can run air for a short time . I wouldn't run it for any more time then absolutly needed , but you can do it . The understanding I got from it was that the moisture in air will or can cause rust in the shock . Why not just charge them up with nitrogen or leave them alone till you can ??

Dan Vance

[In_the_works]

I suppose I could drive shock-less to Fallbrook to get them charged, or bum a ride.

[Greg]

Better to have some pressure to keep the dividing piston from slamming into the res. end cap than no pressure. I've heard all the arguements why shop air is bad, and there isnt enough moisture to do any damage to the inside of an aluminum res can thats covered with a layer of oil.

[kjmiller1]

good thing someone smarter came along http://www.race-dezert.com/vb3/attachments/old/images/graemlins/grin.gif

[UndercoverFab]

if theres a welding shop close by you can just get them filled there, assuming they have a fitting to connect to them, theres nobody in pennsylvania that fills shocks and thats what i did.

[JeffS]

Always try your local Motorcycle shops too. Most new Hondas, Yamahas, and other atv's / bikes / snowmobiles need nitrogen in their shocks or forks, and they all use a schraeder valve like your reservoirs.

My local Honda shop always hooks me up.

[In_the_works]

Thanks for all the replys, I'll have them charged tomorrow for sure.

[J_Dog]

This may sound dumb, but if I don't ask I won't know. We have King 2.5" prerunner bypasses on our 7S truck. Do these things lose their nitrogen charge a lot? If so, do you just check it with a regular tire air gauge off the schrader valve? What should the normal pressure be? Thanks.

[desertracer]

We usually try to check the nitrogen in our shocks every time out. After a race or a lot of testing I think it is a good idea to check them to make sure your shocks stay consistent. It seems that with the heat cycles them tend to lose a bit of pressure. You are going to need more than a tire gauge to check them because they shoud be up around 180-200psi depending of preference, we run our fox's at 180. Fox makes a nice gauge that goes up to 300 psi that screws onto the schrader valve so you can check it. Might give Kartek a call, thats where we got ours. Hope this helps.

[Bomber52]

One of the main reasons for using nitrogen is beacause it is an inert gas (it cannot burn). If a shock filled with normal air gets to hot it could explode.

It is generally never a good idea to run shocks without gas as some seals seal better under pressure and the valving characteristics are likely to change.

If you need to use the vehicle for a short distance, normal air will not do any damage, just make sure you purge the gas chamber with nitrogen when you have the shocks gassed, otherwise they could start to rust if it is a steel housing.

[1992f150]

paintball shops carry nitrogen, possibly a dive shop too.
The pressure is different for each company. Fox told me 200 psi, I think King and SAW want 150 psi.
What I found from my foxes was they dont seem to hold much volume of gas, so that little bit that leaks out when you stick a gauge on tends to make a noticeable drop in psi. Checking it too often might vent a lot of the gas out. These were 10" 2.0's though, perhaps the bigger shocks hold more gas inside?

[Kritter]

Kartek has a tool to eliminate the gas escaping from checking pressures and filling.

[slimjim]

i had a gauge that fox made for checking the shock's pressure on my dh mountain bike - the psi went pretty high, and maybe it would work for checking the shocks on your truck also. it was about $25 at a local bike store.

[ntsqd]

</font><blockquote><font class="small">In reply to:</font><hr />
One of the main reasons for using nitrogen is beacause it is an inert gas (it cannot burn). If a shock filled with normal air gets to hot it could explode.

[/ QUOTE ]

No, no, no.

What you're implying is a Dieseling condition when using a gas other than Nitrogen. Not sure what the autoignition temp of damper oil is, but I'm quite sure it is higher than diesel fuel. "Normal air" is 70% Nitrogen anyway.
IF you ever get a damper that hot you have a real problem, BEFORE it explkdes.

The main reason for using nitrogen is because it changes it's volume very little with a large change in tempature.

[In_the_works]

Maybe he was talking about pure oxygen? Donno who would do that though.

[CHASE550]

The thing with runnig air is the rust factor due to the moisture, but a king shock has a aluminum ressivor and it's internals are also aluminum so the rust factor is not a problem, so in a King you can run air for as long as you want. By the way I work at King and that is what Brett says.

[drtdevil93]

air expands a lot under heat, nitrogen expands very little. now consider that water boils at 212, and shock temperatures in the mid 200's are not uncommon, now you have boiling water in your reservoir? that doesnt sound so good. dont forget all the other junk in our air, at least with nitrogen, you are putting in a pure, inert gas. and lastly, how are you supposed to accurately meter the pressure you are putting in the shocks? a compressor?

erik

[Timmah]

First of all, put shop air in your shocks if you want, but Pete will only laugh at you!!!!! Nitrogen is dry and doesn't expand like air when it heats up (as already stated by others).

Eric, I see your point about the moisture boiling, but at that high of a pressure, I wonder what the boiling point would actually be, 400 or 500 degrees? Not that it matters, just food for thought.

[drtdevil93]

i know, i know... you got my point though...

put air in your shocks, pull leaves out of your springs, dont gusset your cage, dont cycle your suspension.... just be lazy, dont think and then go race on it and scratch your head when things go wrong.

erik

[Kritter]

Hey Erik...how about nitrogen in the shocks, cycle them, gusset the cage, but pull leaves out?

[Greg]

I think i may have mentioned this before, but wouldnt you want the pressure to increase as the shock heats up/ gets used? I lmow the herbsts use a system to actually stabilize nitrogen pressure, but thier shock shafts are on the large side possible leading to a jacking effect from nose pressure. But on a 7/8 shaft i dont see why a slight increase in presusre for heat expansion would be bad. Also, if you put air in your shocks, isnt there just as much moisture "outside" the shock as there is on the insde, as far as rust goes? Also, ive never seen anyone purge the ambient air from a shock before charging it with nitrogen. Im not advocating air, but if you could get 250 psi of shop air, my guess is that you would never know the difference.

[ntsqd]

Oxidation is accelerated in heated or super-heated conditions. Witness a cutting torch. That is super-accelerated oxidation. So under that use shop air would be more corrosive.

Nitrogen isn't a constant pressure regardless of temp, it's just that it's T vs. P curve is not as steep as the curve for ambient air.
You wouldn't, or perhaps I should say I wouldn't want the charge pressure changing with temp any more the necessary. I don't need yet another uncontrollable variable.