Alternative for nitrogen in rear shock

I am in a pinch with a (possible)needed rebuild on a rear Showa shock. I have all the parts but have not figured out how to charge the shock with nitrogen. I am in Peru and there is no such thing as a motoshop around that can fill the chamber. Can i use compressed air or something else that might be available?

The symptoms of the suspension is that when i put weight on the seat, it goes down just a little ways and then stops. It feels like it has about 2 to 3 inches of travel. Something is not right. This is my first ever rear suspension problem in the 25 years of bike life. Any love out there?

Can't use compressed air, my buddy went to bicycle shop and bought a high pressure hand pump. He has to check it every so often since sir fluctuates with weather

I have used ordinary compressed air.  A bicycle shock pump is better though.  You can charge it up to the full pressure and do so more consistently.  I haven't bothered with nitrogen in years.

Don't use compressed air unless it has a water filter to remove moisture ,a mtb pump is a better option

Nitrogen won't change pressure when it heats up. Regular air will.

Sweet. A bicycle shock pump might be available. Lots of high end mtb's around here. Thanks for the insight folks.

All gases expand with increases in temperature ,just like air- in line with boyles law ,if the air has moisture in it you will have problems

Edited by mog

Are you sure it's the shock causing the problem? I would start by making sure the linkage bearings are clean and well greased.

80% of the air we breath is nitrogen so only 20% of the shock air volume will be affected by temperature...not sure if a lot of us can feel the difference.

Usualy I'm a 'do it the right way or don't bother' / follow the service manual to the letter type of mechanic but,

after servicing both my YZ125's and buddy's CRF250R shock's this winter,

I've opted for the 0-300psi mountain bike air pump option rather than using nitrogen this season.

 

I'd rather have to check / re-set the pressure easily anytime as needed than setting it to 140psi of nitrogen

and then not checking it all season long and hoping it holds the proper pressure as most people probably do.

 

For our very recreative MX usage, (10 lap 'amateur level' sessions then a rest),

I doubt we'll see any difference in pressure build-up between 78.09% and 100% nitrogen.

 

I do initialy pump up the bladder in as much a non-humid area as I can, say inside the house versus a damp workshop.

Edited by mlatour

All gases heat up and expand on the same way.

 

https://en.wikipedia.org/wiki/Gas_laws

 

Our air is 80% Nitrogen

 

The problem behind using air is 2:

 

- Humidity. when it turn in vapor. It expands A LOT increasing pressure.

 

- Oxidation. Oxigen and water vapour can degrade steel pieces and the oil.

 

But, beeing using air from bicicle shock pump from 2 years....let's see on the day I disassemble that shock again.

 

https://picasaweb.google.com/109136997962080302876/Trial#6050862301577397138

 

It's a Ollé trials shock (Sherco)

I rebuild suspensions for a living.  As previously stated, the only real difference between nitrogen and compressed air is moisture.  All air has moisture in it weather compressed by a bike pump or air compressor.  There are two main reasons shops use nitrogen.  1. 100% perfectly dry.  2. Convenience.  Nitrogen tanks are cheap and have 3,000 psi of nitrogen in them.  Shocks take between 150-250 psi in them which is beyond the reach of most air compressors.  Since most modern motorcycle shocks are of a DeCarbon design with a piston or bladder separating the nitrogen charge from the oil, there is little chance any moisture in the air will mix with the shock oil.

 

All gasses expand at the same rate.  It is Boyle's Gas Law of Physics.  And, the air you breathe is 78-79% nitrogen.  Remember these two facts when a tire shop tries to sell you nitrogen for your tires.

 

When I am in the field doing testing, I use a mountain bike pump to pressurize shocks.  No issues.  You can use air until the cows come home with not a worry.

I use argon/co2 (no moisture) gas from my mig welder.  I bought a regulator and a No-air-loss chuck so I take care of my shocks and my friend's shocks. 

Just got my first full suspension MTB last fall, and yes, somehow we're all running 150-200 psi of air in MTBs all this time without problems. And that little rear shock can get quite a workout.

I've used both nitrogen and an MTB shock pump.  Never noticed a difference in "feel", nor did I ever expect to.  Since I go through my stuff more frequently than most anyway, I'm fine with the air pump.  If I were expecting to set it and forget it for 50-100 hours, I'd probably use nitrogen in case there was some long-term issue.  At 55 hours, the OEM bladder on my 450 is still in perfect shape from using air most all the time.

 

Every once in a while I'll check it.  No loss, except for the amount required to pressurize the pump gauge which I factor in (about 5psi at that volume).

Just to make everyone aware after around 25 hours a good amount of gas goes into the oil ,so no one should go much longer than that

Just to make everyone aware after around 25 hours a good amount of gas goes into the oil ,so no one should go much longer than that

Even with a piston :) :)..To the op if you want nitrogen find a refrigeration mechanic they use it often.

Lol no pistons generally transfer much less as the surface area is much smaller of a o ring vs a bladder

80% of the air we breath is nitrogen so only 20% of the shock air volume will be affected by temperature...not sure if a lot of us can feel the difference.

As posted the prob with air is the moisture and oxygen.  The moisture changes the temp/pressure behavior of the gas. Oxygen is a very corrosive gas and becomes even more so at high pressure, and the moisture makes it more so.

So any dry no oxygen gas is good, and as posted nitrogen is common and readily available, but so is CO2. I have a small CO2 paint ball tank that I clip to my waist to operate air tools. I can also use it to inflate tires and the regulator goes to 200psi. Leakless chucks are avail on ebay.

 

I rebuild suspensions for a living.  As previously stated, the only real difference between nitrogen and compressed air is moisture.  All air has moisture in it weather compressed by a bike pump or air compressor.  There are two main reasons shops use nitrogen.  1. 100% perfectly dry.  2. Convenience.  Nitrogen tanks are cheap and have 3,000 psi of nitrogen in them.  Shocks take between 150-250 psi in them which is beyond the reach of most air compressors.  Since most modern motorcycle shocks are of a DeCarbon design with a piston or bladder separating the nitrogen charge from the oil, there is little chance any moisture in the air will mix with the shock oil.

 

All gasses expand at the same rate.  It is Boyle's Gas Law of Physics.  And, the air you breathe is 78-79% nitrogen.  Remember these two facts when a tire shop tries to sell you nitrogen for your tires.

 

When I am in the field doing testing, I use a mountain bike pump to pressurize shocks.  No issues.  You can use air until the cows come home with not a worry.

I agree but the moisture has more to do with changing the behavior of the gas. And some of the gas/moisture will go thru the membrane or past the piston seal. Even head gaskets leak a small amount of combustion gas into the coolant, which changes the Ph of the coolant and causes corrosion issues.

My opinion is using air is not a big issue and more frequent servicing of the shock will correct any problems. Progressive Suspension sells a small hand pump with an optional pressure gauge that goes high enough for shocks.  http://www.progressivesuspension.com/product/1468/mini-gauge-pump

do you have an airport nearby?They usually have nitrogen!

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