Compressed air vs Nitrogen - gas shock refill

[MotoKuzzi]

The original marzocchi rear shocks on my '97 California are hydraulic oil over gas if that makes sense. I recently had them apart to change the oil and in the process dumped the compressed gas in the reservoir.

When I reaasembled them I put a charge of compressed air in to see what effect it had ( not reinstalled to the bike ) and was pleasantly surprised how well they seemed to work.

My question is, apart from the obvious effect of reduced gas loss to the system that nitrogen offers (which I could over come by regular topping up with air) what advantage would refilling with Nitrogen give me? Is there any potential damage that compressed air could cause, e.g. damage to rubber / metal parts through moisture and corrosion?

The compressor I'm using is one of those small battery powered electric jobs so I would have thought the air would be less laden with the oil etc that a larger compressor would produce. :Oops:

[OllyMoto]

My understanding of it would be that the main benefit in this situation would be thats Nitrogen gas is affected less by the heat build up through use. Works on the same principles of why some cars are reccomended to have tyres filled with nitrogen.

Olly

[CookMySock]

damage to rubber / metal parts through moisture and corrosion? Yes, this. If you could find a way to dry the gas and consume the oxygen out of it...

[ducatilover]

The air we breathe is around 78% nitrogen.
The moisture content of the gas has a greater effect on its expansion rates as it heats than the fact that it is nitrogen, or 78% nitrogen.
Unless you're running in Le-Mans where the incredibly extreme temps of constant shock oscillations is a factor, than I very highly doubt you will ever notice the difference between the two... what you should do, is fill 'em in the driest/least humid conditions you can.

[Coldrider]

Nitrogen is an inert gas, so doesn't "normally" have any chemical reactions, which includes oxidation etc. Nitrogen is also used to dispel oxygen and thus moisture.

If you have one shock charged with air and onther charged with nitrogen, after five or so years if you pull them apart you would probably find why the sealed shocks used nitrogen.

[Pussy]

Nitrogen is an inert gas, so doesn't "normally" have any chemical reactions, which includes oxidation etc. Nitrogen is also used to dispel oxygen and thus moisture.

If you have one shock charged with air and onther charged with nitrogen, after five or so years if you pull them apart you would probably find why the sealed shocks used nitrogen.

Nitrogen is not an inert gas.

[Coldrider]

Nitrogen is not an inert gas.It is not a noble gas, but has the properties of an inert gas, which is why it is cheap.

[slowpoke]

Bad move, the compressed air will oxidise and degrade the oil, which will ultimately affect the damping qualities of the shock.

We use oil as a heating medium where I work and have a gas "blanket" on the large storage vessel to remove oxygen and stop the oil oxidising. We also have a nitrogen plant that produces 98% pure Nitrogen, yet even that isn't adequate to stop the oil degrading so use dehydrated natural gas to blanket the oil and ensure it isn't oxidised.

[Robert Taylor]

The original marzocchi rear shocks on my '97 California are hydraulic oil over gas if that makes sense. I recently had them apart to change the oil and in the process dumped the compressed gas in the reservoir.

When I reaasembled them I put a charge of compressed air in to see what effect it had ( not reinstalled to the bike ) and was pleasantly surprised how well they seemed to work.

My question is, apart from the obvious effect of reduced gas loss to the system that nitrogen offers (which I could over come by regular topping up with air) what advantage would refilling with Nitrogen give me? Is there any potential damage that compressed air could cause, e.g. damage to rubber / metal parts through moisture and corrosion?

The compressor I'm using is one of those small battery powered electric jobs so I would have thought the air would be less laden with the oil etc that a larger compressor would produce. :Oops:

Dry / purified air you will get away with, meaning it has to come from a cylinder supplied by one of the gas supply companies. But if you do that its as well to use the PROPER INTENDED GAS, nitrogen. Filling it from a small electric compressor means there is 100% chance that you are drawing in lots of moisture and given that theres a lot of rainfall at present we have high humidity content.
I disagree totally with someone else who said to the effect ''this is not LeMans, dont worry''. Given that we have a high ratio of bumpy roads it challenges the suspension moreso than relatively smooth racetracks. You get lots of suspension shaft movement so therefore lots of gas pressure fluctuation and heat buildup.
If there is a seperating bladder oil contamination is not so much of a risk but given the above you dont need to risk the possibility of bursting an often hard to source bladder for want of having the extra security of installing a more suitable and purified gas. If it is emulsion type then yes Slowpokes comments about oil contamination and corrosive elements is very valid.
The danger of asking such questions on such forums is too often you will get ''she'll be right'' answers, the number 8 wire mentality doesnt cut it.

[bogan]

Shit, thats what I forgot to do, 8 months ago! Gassed up my shock from the compressor when I was pissing about with different oil viscosities and forgot to replace it with nitrogen afterwards. Cheers for the reminder!

[MotoKuzzi]

Thanks for all the comments - taking everything into consideration Nitrogen appears to be the safest option, if it was simply a case of pressure loss I would take the punt and refill more often which can be done easily with the tire valves fitted at the base.

[ducatilover]

Shit, thats what I forgot to do, 8 months ago! Gassed up my shock from the compressor when I was pissing about with different oil viscosities and forgot to replace it with nitrogen afterwards. Cheers for the reminder!

Did your shock explode and kill you?

[Icemaestro]

I had my cbr600 shock re oiled and gassed just recently - when he pulled it apart there was just air in it...it wasn't performing great but I'm still in one piece (just 1 small crash...)

[Coldrider]

Did your shock explode and kill you?nitrogen boils off at -196 deg c, and comes pre-exploded as earth inherited nitrogen from a super nova.

[ducatilover]

nitrogen boils off at -196 deg c, and comes pre-exploded as earth inherited nitrogen from a super nova.

Been cold here lately.

[Coldrider]

Nitrogen is not an inert gas.you'll need at least 500deg c at 200 atmospherses (5878 psi) and chuck in some iron as a catalyst to get a chemical reaction, the average shocky should be OK.

[Robert Taylor]

Did your shock explode and kill you?

We have seen a number of shocks over the years that have burst their gas bladders BECAUSE they were filled with compressed air out of an everyday compressor. And I think its fair to say that we have been inside a few more shocks than you have.
Its all about minimisation of risk. Would you care to explain why nitrogen is the charging gas of choice?

[F5 Dave]

Did your shock explode and kill you?
he didn't say he used oxygen. Apparently that's a good way to hurt yourself given a bad set of circumstances.

hey look at my motto thing under my user name. No.8 wire & all.:laugh:

[ducatilover]

Would you care to explain why nitrogen is the charging gas of choice?

Has already been done, now apparently I'm going to die because my forks have air in them. Oh well.

[Robert Taylor]

Has already been done, now apparently I'm going to die because my forks have air in them. Oh well.


Forks are of course a slightly different kettle of fish when it comes to gas volume and displacement of that volume, secondary ''trapped air spring compression ratio'' being very much one of the main tuning parameters. And thats significantly different to a very low volume of gas at often very high pressures and higher temperatures.
If you read and understood my explanation properly it inferred nothing of the sort of emotive claptrap that you have espoused, why such stupid innuendo? My post explained the negatives of doing something that ( largely ) doesnt concur with manufacturers requirements, and was about reasonably well qualified information, not invective. ( But what would manufacturersand those that they train know????)
Wo betide those who dare to ''stick their head above the parapet'' by having the ultimate temerity of posting on forums advising the correct way to do things. In doing so inevitably correcting those who may have posted with well meaning intent but nonetheless without being totally correct, sometimes quite incorrect. Clearly the many years that I have personally spent working with suspension and training overseas with 3 leading manufacturers have taught me nothing? Thankfully most people will accept good and 100% accurate advice in the spirit that it is given, without recourse to the less appealing sides of human nature.

[bogan]

Would you care to explain why nitrogen is the charging gas of choice?

Pun intended? I paid 20 bucks for a fill last time :shifty: What's argon or argosheild like as a shock refill gas anyway?

[slowpoke]

Has already been done, now apparently I'm going to die because my forks have air in them. Oh well.

Duuude, you're getting free technical advice, take it in the spirit it's given.

Nope your shock isn't going to explode and kill ya but even someone like me who's few remaining brain cell's complain of loneliness can envisage a scenario where crap suspension performance can be the difference between making it 'round a potholed/rock strewn corner and not, or stopping short of a u-turning car rather than bottoming the forks and slamming into it because your fork oil is emulsified.

May/probably never happen but it's the shortcut you're defending that has increased the possibility.

[ducatilover]

Forks are of course a slightly different kettle of fish when it comes to gas volume and displacement of that volume, secondary ''trapped air spring compression ratio'' being very much one of the main tuning parameters. And thats significantly different to a very low volume of gas at often very high pressures and higher temperatures.
If you read and understood my explanation properly it inferred nothing of the sort of emotive claptrap that you have espoused, why such stupid innuendo? My post explained the negatives of doing something that ( largely ) doesnt concur with manufacturers requirements, and was about reasonably well qualified information, not invective. ( But what would manufacturersand those that they train know????)
Wo betide those who dare to ''stick their head above the parapet'' by having the ultimate temerity of posting on forums advising the correct way to do things. In doing so inevitably correcting those who may have posted with well meaning intent but nonetheless without being totally correct, sometimes quite incorrect. Clearly the many years that I have personally spent working with suspension and training overseas with 3 leading manufacturers have taught me nothing? Thankfully most people will accept good and 100% accurate advice in the spirit that it is given, without recourse to the less appealing sides of human nature.
:laugh: Goodness me Robert, I'm pulling yer leg here, not everyone is out to argue with you on the net, and I for one don't doubt your wisdom.
Bunch of panty knotted nutters today aren't we?

I'll happily admit I have learned something from you each time you post :niceone:
But, our air is 78% nitrogen and moisture is a large contributor to gas expansion rates, so I will happily go on believing that and now knowing what you've pointed out.

[Robert Taylor]

:laugh: Goodness me Robert, I'm pulling yer leg here, not everyone is out to argue with you on the net, and I for one don't doubt your wisdom.
Bunch of panty knotted nutters today aren't we?

I'll happily admit I have learned something from you each time you post :niceone:
But, our air is 78% nitrogen and moisture is a large contributor to gas expansion rates, so I will happily go on believing that and now knowing what you've pointed out.

No worries, its always of course hard to desseminate in written form how much is leg pulling and how much is deliberate mischief.
Youve nailed it in mentioning the adverse effect of moisture in the air. In various parts of the world that air can also be quite corrosive and we see a lot of corrosive damage inside and outside suspension units from motorcycles and cars first sold and used in Japan.

[Robert Taylor]

Pun intended? I paid 20 bucks for a fill last time :shifty: What's argon or argosheild like as a shock refill gas anyway?

Those alternatives I havent studied but given that nitrogen is reasonably accessible I think its a no brainer to stick to the ideal and recommended gas for the application.
With our Ohlins products we have a 5 year warranty, I would be loathe to honour a warranty claim where a gas other than the recommended nitrogen was used, that would also perhaps suggest that other ''compromises'' were acceptable to the owner.

[ducatilover]

In various parts of the world that air can also be quite corrosive and we see a lot of corrosive damage inside and outside suspension units from motorcycles and cars first sold and used in Japan.
I have wondered about that briefly before, I'd like to know why/how, off to Google I go!

[Flip]

Nitrogen is dry and cheap, thats all.

Just go to beaurepairs.