How do I refill nitrogen??


20 replies to this topic
  • ola_sandin

Posted October 31, 2006 - 10:11 AM

#1

How do I refill nitrogen in my Wilbers shock absorber? There is no nozzle, only a screw. Do I need some special equipment to fill the gas?

//Ola

  • SpringChicken

Posted October 31, 2006 - 10:30 AM

#2

I've always been told to let a professional do that. I guess it can be really dangerous if you don't know what you're doing. You could get hurt. Take it to a suspension tuner and pay him to service it.

  • marty b

Posted October 31, 2006 - 05:20 PM

#3

nitrogen is suplyed in a bottle simaler to oxigen for welding, you run it through a regulator to a managable pres, about 100- 150psi
the equipment is expencive so it is cheaper to get it done. the ones with a screw insted of a "shrader" valve have to be done with a needle

  • justarider

Posted October 31, 2006 - 05:28 PM

#4

Take it to a shop, DO NOT USE AIR. I've seen a shock reservior blow apart out in the desert. The guy said he pumped it up with a big hand tire pump and when it got hot, it literally blew the side out of the reservior, right into the guys leg. They called the ambulance and he went away in the ambulance. Everyone who saw it was shocked, wow, none of us have ever seen that before. Dude, don't use air, have a professional fill it.

  • ola_sandin

Posted November 01, 2006 - 06:57 AM

#5

Thanx for the answers.:mad: I think I´ll leave it to some one with the right gears and skill.

  • lucky_logger6

Posted November 02, 2006 - 01:26 PM

#6

I Would recommend taking it to a shop too, but Costco uses nitrogen around here (Ridding, Ca) to fill tires so if you can figure the rest out maybe for a tip they would help you with the nitrogen.

  • velosapiens

Posted November 02, 2006 - 02:00 PM

#7

I Would recommend taking it to a shop too, but Costco uses nitrogen around here (Ridding, Ca) to fill tires so if you can figure the rest out maybe for a tip they would help you with the nitrogen.


if you have a nitrogen tank and high-pressure regulator, it's easy. one of my buddies helped me revalve the suspension on my old klx. he was a brewer too so we had nitrogen already, but a low-pressure regulator (nitrogen is good bubbles for stouts). he picked up a high pressure regulator cheap and we were able to charge the shock pretty easily.

but if i were doing it again, and my buddy weren't available, i would just pay someone to do it instead of buying the equipment.

  • KDXGarage

Posted November 03, 2006 - 06:11 AM

#8

The problem with the usual home made (or tire inflation) setup is that the chuck involved is not going to be the right kind to allow it to maintain the pressure after the chuck is released.

  • mxhowes

Posted November 28, 2006 - 04:05 PM

#9

For a home made system you need a #556 Shhrader valve connection .....
http://www.skygeek.com/556.html

Let's see.....

Buy one 21 cf N2 tank filled ......$91
200 psi regulator Old, used .......$20 new ~$100
Schrader valve connection $32

So for ~$140 you will be able to fill shocks, buy more fittings and you can make and keep beer, fill paint ball guns etc.

Jim
(in the process of building a fill station)

  • RCannon

Posted November 28, 2006 - 05:50 PM

#10

Take it to a shop, DO NOT USE AIR. I've seen a shock reservior blow apart out in the desert. The guy said he pumped it up with a big hand tire pump and when it got hot, it literally blew the side out of the reservior, right into the guys leg. They called the ambulance and he went away in the ambulance. Everyone who saw it was shocked, wow, none of us have ever seen that before. Dude, don't use air, have a professional fill it.


Why would air cause this to happen? Regular old air that we breathe contains more nitrogen than anything else. The air pumped in to a shock would contain some moisture, but I cannot imagine anything else causing problems.

Was the guy on a KTM and his boot finally rubbed through the reservoir?

  • nscmj3

Posted November 28, 2006 - 07:28 PM

#11

air expands at a much lower temperature than nitrogen does. Nitrogen is used in airplane tires for precisely that reason...they wont explode as they go from 0mph to 140mph + upon landing. Car tire dealers are starting to use nitrogen as it's more stable and doesn't lose pressure from heating/cooling like atmosphere air does.

  • RCannon

Posted November 28, 2006 - 07:47 PM

#12

I understand that premist, but regular old air we breathe is mostly nitrogen. The small amount of impurities will not cause a strong aluminum vessle, like a reservor, to explode.

A car tire at 30 psi and 70 degrees does not explode when the tire temp hits 120 (hot summer day) or 140 degrees rolling down a Phx freeway. Yes, pressure will increase, but not enough to blow things up.

Yes, air is a poor choice for a shock pressure system. However, it will not blow things up.

I think oxygen may be a problem or some other flamible gas, but not air.

By the way, ANYONE who pays for nitrogen to be installed in their car tires has a screw loose. Unlesss the tire store was to vaccum down your tires before inflating (impossible because the bead is not seated) they still have air in them.

One possible advantage is that nitrogen is clean. Your not adding dirt and junk from a poor airhose. I think this is the main advantage for airplane tires.

I am just bitter because I did not think of the idea first. Nitrogen tanks are filled for virtually nothing. Your looking at straight profit. Nitrogen mollecules are also larger than normal. It will tend to no tlose pressure as quickly as other materials. Try pumping a tire up with co2 sometime. Notice how quickly it goes flat.

I have also been known to refill motorcycle tires using straight refrigerant..R12, whatever is handy. You get some very odd reactions doing this!

  • nscmj3

Posted November 28, 2006 - 09:51 PM

#13

[quote name='RCannon']I understand that premist, but regular old air we breathe is mostly nitrogen. The small amount of impurities will not cause a strong aluminum vessle, like a reservor, to explode.

A car tire at 30 psi and 70 degrees does not explode when the tire temp hits 120 (hot summer day) or 140 degrees rolling down a Phx freeway. Yes, pressure will increase, but not enough to blow things up.

Yes, air is a poor choice for a shock pressure system. However, it will not blow things up.

I think oxygen may be a problem or some other flamible gas, but not air.

By the way, ANYONE who pays for nitrogen to be installed in their car tires has a screw loose. Unlesss the tire store was to vaccum down your tires before inflating (impossible because the bead is not seated) they still have air in them.

One possible advantage is that nitrogen is clean. Your not adding dirt and junk from a poor airhose. I think this is the main advantage for airplane tires.



QUOTE]


From the FAA website:

A tire explosion can be prevented by the use of an inert gas such as nitrogen for tire inflation.
Laboratory tests conducted in 1973 show a definite relationship between the quantity of oxygen in a tire and the gas mixture's autoignition temperature. Test data indicate that at nitrogen concentrations between 80 percent and 90 percent (the atmosphere contains approximately 80 percent nitrogen and 20 percent oxygen), ignition of inner tire liner samples occurred in a test chamber with temperatures varying from 478 °F. to 518 °F. Nitrogen concentrations between 90 percent and 95 percent raised the autoignition temperatures to a range of 520 °F. to 531 °F. At nitrogen concentrations greater than 95 percent, there was no pressure increase in the test chamber, even at chamber temperatures of 670 °F., indicating that there was no ignition. Based on these tests, it was concluded that any concentration of oxygen in a tire in excess of 5 percent of the total gas will support a reaction. At a concentration above 10 percent, this reaction is an abrupt autoignition. At concentrations from 5 percent to 10 percent, this reaction is assumed to be a low level autoignition, based on measurement of test chamber pressure and temperature.




I'd like to meet the guy that can heat his car tires up to 500deg f! I think the biggest "benefit" to using nitrogen is this: (from a website discussing this very topic):

The air around us is full of water vapor. Compressing air concentrates the water in it. Draining the water from your compressor tank daily helps, but unless you have a really efficient air dryer system, chances are that there's a lot of water in your compressed air.
When you compress air, it takes up much less volume, but the percentage of water by volume is greatly increased...Water vapor in compressed air acts as a catalyst, accelerating rust and corrosion. Water vapor also absorbs and holds heat. And when it changes from liquid to vapor, water expands tremendously in volume.

As a result, tires inflated with wet air tend to run hotter and fluctuate in pressure more. That's one of the reasons why racing tires, where fractions of a psi can radically change the handling characteristics, are inflated with dry nitrogen.


For me, the water vapor arguement alone is worth the price of filling with nitrogen!! Those shocks are expensive!! Why risk corrosion? I'm not sure about the exploding shock part, but it stands to reason that it's possible.

  • CR2CRF

Posted November 28, 2006 - 09:52 PM

#14

Bicycle pump air is 78% nitrogen. There is no way that guy's shock res failed due to air rather than nitrogen. He may have over pressurized it to begin with or something else may have been wrong with the shock before the air was introduced. But air was not the cause of the failure.

  • KDXGarage

Posted November 28, 2006 - 10:00 PM

#15

If the manufacturers could save a penny by using regular air instead of nitrogen, they would have been doing it for years. Since they have millions of dollars to research it all, then I will just keep copying them. :-)

I think part of the airplane tire nitrogen use is related to the altitude and related pressure issues.

  • nscmj3

Posted November 28, 2006 - 10:01 PM

#16

I guess my previous post was maybe a little to technical?

  • RCannon

Posted November 29, 2006 - 06:18 AM

#17

I guess my previous post was maybe a little to technical?


Hell no is wasn't. It answered the question I had. I very much appreciate it.

I'll tell you what. When I buy my 747 or DC 10 (undecided at the moment) I am going to fire the mechanic if he adds aie to my tires!

I have all the free nitrogen I want. I can use a bottle a week if I want to. I might start using it in mt cycles. The hell with the cars, who cares about them anyway!

  • thillsam

Posted November 29, 2006 - 10:48 AM

#18

From the FAA website:

Test data indicate that at nitrogen concentrations between 80 percent and 90 percent (the atmosphere contains approximately 80 percent nitrogen and 20 percent oxygen), ignition of inner tire liner samples occurred in a test chamber with temperatures varying from 478 °F. to 518 °F. Nitrogen concentrations between 90 percent and 95 percent raised the autoignition temperatures to a range of 520 °F. to 531 °F. At nitrogen concentrations greater than 95 percent, there was no pressure increase in the test chamber, even at chamber temperatures of 670 °F., indicating that there was no ignition.



On some shocks(that use a floating piston instead of a rubber bladder), there is nothing but an O-ring to combust inside of a Shock reservior - and even that has an extremely high flash point even in the presence of more than a ~20% Oxygen mixture. Somewhere there is post up on TT here where all the pro suspension guys were measuring shock temperature and damping changes(also gas-spring shaft forces as a result of pressure increase from temperature) at a given temperature. I recall them getting shocks ot like 300+ deg F, enough to seriously multiply the pressure inside a shock reservior even filled with Nitrogen. I know from my crude infra-red temperature gun that it's not very hard to get a shock to 220+ deg F just by riding whoops hard and continuously, but this is still drastically below flash point even in the presence of pressurized oxygen-rich mixtures.


That's one of the reasons why racing tires, where fractions of a psi can radically change the handling characteristics, are inflated with dry nitrogen.


Most "racing tires" that anyone bothers to fill with Nitrogen are used for asphalt racing, where fluctuating tire pressures cause many things in a tire. Inadvertant stagger change, sidewall stiffness, etc...but the greatest changes is in contact patch force distribution, which directly affects adhesion limit - the most important factor of them all. Stagger is only important on oval racers , and is less of a factor than the contact patch is.


All of that said, I live in AZ where relative humidity rarely exceeds 15% unless it just rained. My bike has a floating piston(no bladder), and I use an MTB air shock pump and leave the pressure ~10-15% less than I would with Nitrogen and I've never had a problem with it.

Curse me if you will, but MTB air shocks are frequently filled to DOUBLE the pressure of a motorcycle shock reservior with *gasp* regular air, and you've never heard of them exploding and sending someone away in an ambulance have you? Think about it also: in an air spring shock, the air pressure probably quintuples(or greater) when it is bottomed, too. No explosions I've ever seen or heard of, even on the professional NORBA circuit for a couple of years.

Using an air compressor to fill a shock, on the other hand, is indeed a big risk. The air in a compressor tank is subject to pressurization and confinement inside a smooth-surfaced pressure vessel, whos walls are frequently chilled by ambient air - all contributors to inside surface condensation, which drains to the bottom and humidifies the air that is contained within the tank when it is filled again to very high humidity.

Nitrogen is better, it's standardized. Any variable you cna take out of the equation is better, always, but air will work almost as good. I would challenge anyone to tell a seat-of-the-pants difference between a shock filled with very-low humidity air - or - one filled with Nitrogen.

It would be interesting, though, to put a gauge on the reservior to see how much the temp fluctuates with temperature though, eh?


http://www.cartalk.com/content/columns/Archive/1997/September/05.html


  • thillsam

Posted November 29, 2006 - 11:12 AM

#19

From the FAA website:

A tire explosion can be prevented by the use of an inert gas such as nitrogen for tire inflation.


Nitorgen is not inert, either, it is largely unreactive at most realistic temperatures, but the fact that it occurs as a bonded molecule in all sorts of compounds we use all the time, as well as in our bodies/nature, means it is not Inert like Argon or anthing on the far right side of the periodic table...

  • elevatorjunky

Posted November 30, 2006 - 07:42 PM

#20

I was doing research in this forum about nitrogen,I was happy to see it being discussed so recently.I am impressed at the knowledge I have read in this thread and was hoping to ask a related question.Assuming I have all the capabilities,can I add argon to a shock instead of nitrogen?I have this welding gas not nitrogen.If it matters I am using it in a bladder shock off a 05 dr650se-.I am not cheap,I just dont like others touching my stuff.I like to be self sufficient and as far as I know argon is a truly inert gas.But for this intended purpose I need advice from you.Also why is air such a problem I do pump 150lbs in my mountain bike shock and my friends Harley all the time?I even have a shock pump.





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