[RotoRooter]

A question for all the suspension tinkerers out there: As I'm working on my El Jefe tomorrow (I managed to break the banjo bolt that connects the reservoir hose to the shock body. Don't ask...), I'm wondering if I can get any benefits from recharging the reservoir with nitrogen instead of air? Certainly, nitrogen is most often used in this application since it doesn't expand with heat as air does. That being the case, why do you suppose that Stratos recommeds charging with air?

Satisfy my curiosity, please...

 

[mandown]

wow, they told you to use air? that seems odd to me. i owned a jefe for a while. i never charged it though (bad owner that i am). however, many peeps seem to believe that the shock is a copy of the avy design. the avy is nitrogen charged. i would double check the manual and call stratos back.

 

[denjen]

A question for all the suspension tinkerers out there: As I'm working on my El Jefe tomorrow (I managed to break the banjo bolt that connects the reservoir hose to the shock body. Don't ask...), I'm wondering if I can get any benefits from recharging the reservoir with nitrogen instead of air? Certainly, nitrogen is most often used in this application since it doesn't expand with heat as air does. That being the case, why do you suppose that Stratos recommeds charging with air?

Satisfy my curiosity, please...

THe jefe can be completly serviced by you. They use the air so you can fine tine it to your liking.

 

[kidwoo]

Something like 72% of ambient air is nitrogen anyway so for the most part, they're pretty interchangible......unless you're smoking a cigarette or near a coal plant when you use your shock pump.

The biggest thing to worry about over composistion is dry gas dry gas vs humid gas. A lot of companies charge their shocks with N2 because it's inert and won't ever corrode anything, but also because "dry nitrogen" is easy to get and guarentees you won't get condensation in you gas chamber. If you live somewhere dry (not the east coast or PNW), you should be able to use either.

 

[SuboptimusPrime]

I'd be curious to see the comparison in the thermal expansion properties of air (78% N2, 21% O2 plus other stuff) vs. molecular nitrogen.

drat, ninja posted me.

 

[kidwoo]

I'd be curious to see the comparison in the thermal expansion properties of air (78% N2, 21% O2 plus other stuff) vs. molecular nitrogen.

drat, ninja posted me.

PV=nRT

As long as everything is ideal.

 

[Tootrikky]

Air is roughly made up of 80% Nitrogen and about 20% Oxygen and 1% Argon. Yeah the numbers don't add up up but they work for quick calculations. Nitrogen is used versues ari in shock becuase Oxygen is very corrosive, while Nitrogen is inert.

Yes you can use Nitrogen in your El Jeffe

 

[SuboptimusPrime]

PV=nRT

As long as everything is ideal.

I know I know...I was just curious how ideal air is compared to N2 which is pretty ideal...

 

[kidwoo]

I know I know...I was just curious how ideal air is compared to N2 which is pretty ideal...

I know for a fact I've got a textbook at home with that answer in it from a fluid mechanics class somewhere. I remember seeing a way to estimate deviations based on humidity, carbon content etc........

It would probably be like reading arabic if I looked at it these days though.

 

[mandown]

Something like 72% of ambient air is nitrogen anyway so for the most part, they're pretty interchangible

The biggest thing to worry about over composistion is dry gas dry gas vs humid gas.

agreed, most "air" is nitrogen. the moisture issue would be the biggest concern.

 

[2phass]

I broke that bolt off too so don't feel bad.

If you look close at the stratos web site is says nitrogen somewhere. The literature I got said air. I spoke with their rep Catherine and she said to charge it with air. DO NOT use air.

I spoke with highly regarded motorcycle suspension tuner and he is strongly advises against using air. This was after I brought my jefe to him to tune and repair. The long DH runs at whistler had my jefe so hot the shaft actually blued. My real life experience says pay the 10 bucks to get it charged at a shop.

P.S that shim stack you are playing with is likely a generic configuation no where near optimal in terms of restricting flow. At least that was the case with me.

Good luck

 

[RotoRooter]

Hey, thanks all, for your responses; they echo what I was suspecting. Perhaps I'll play with air to get the right pressure, then take it into my MX shop to have it re-pressurized with Nitrogen.

2Phass, now you have me curious about how you broke your bolt. I suspect that it was the same way that I broke mine: that banjo fitting they use is awfully bulbous. It's wider than the upper bushings, so mine was trying to be shoved into the shock mounting position at full compression. Obviously, being wider than the bushings, it didn't fit. Sheared it right off and soaked everythng pretty well with oil.

 

[kidwoo]

DO NOT use air.

The long DH runs at whistler had my jefe so hot the shaft actually blued.

How do you know those two are related?

 

[SuboptimusPrime]

It would probably be like reading arabic if I looked at it these days though.

I know how you feel. All my chemistry profs would be very, very disappointed with me if they read this. I guess that's what I get for straying from chemistry and getting into wimpy science...

FWIW, I did find something that said that air approximated an ideal gas within 1%, except at high pressure, low temperature situations, which are certainly not present in shocks...

 

[vitox]

I broke that bolt off too so don't feel bad.

If you look close at the stratos web site is says nitrogen somewhere. The literature I got said air. I spoke with their rep Catherine and she said to charge it with air. DO NOT use air.

I spoke with highly regarded motorcycle suspension tuner and he is strongly advises against using air. This was after I brought my jefe to him to tune and repair. The long DH runs at whistler had my jefe so hot the shaft actually blued. My real life experience says pay the 10 bucks to get it charged at a shop.

P.S that shim stack you are playing with is likely a generic configuation no where near optimal in terms of restricting flow. At least that was the case with me.

Good luck

that is VERY weird.

i have tuned and worked on shock for VERY fast people for quite a few years, ive never bothered with nitrogen because AFAIK the main difference is corrosion and thats not going to be of any real concern within a shocks actual lifecycle.

if your shaft "blued" then i would guess something else is (very) wrong and i would also be very interested in understanding how a steel shaft could get blue without the plastic parts (dust seal and orings in the hose banjo for instance) melting.

i have worked on the jefe btw.


for all I can understand, the single most important factor in that shocks come factory assembled with n2 instead of atmosphere air, is that they can avoid ORM-D restrictions because n2 in considered an inert gas, this means air shipping of bikes frames and shocks being possible or a lot cheaper in most cases.


totally agree with you on the shim stack thing.

 

[DirtyMike]

Hmmm, Well what most forget about with Nitrogen and air is taht Nitrogen in a shock is used to stailize the oil from foaming. Some shocks are Assembled using oils that dont need that to keep it from happening. WHile others use a Nitrogen charge over the Oil, and have a bladder for an air chamber so you can customise your feel better. The whole Nitrogen charged shock idea on Mtn bikes started with Auto's. Your gas shocks on your cars/trucks are Nitrogen charged to stabilize the oil from foaming, hence eliminating fade. doesnt take alot to do it either.

 

[2phass]

Hey Vitox,

I know your a suspension guru and appreciate your feedback. FYI my handle has nothing to do with my riding ability. Ever seen someone called Tiny?

Anyway the shock for sure seriously over heated. I agree it is unlikely to over heat to the point I discribed but I attribute it to the fact the shim stack at the time was likely not bending at all and at 220lbs with out gear it was taxed more than normal. The plastic ring on the banjo was visably distorted from heat but it did not leak. I had to change out the pistion/shaft seal as well.

Once tuned properly and charged with nitrogen it worked awesome. The guy who worked on my shock (two trick racing) tunes factory motorcycle suspension for a living and learned his trade from a former world GP suspension tuner. He was not surprised at all. I am sure air works fine 99% of the time but for 10bux I would just put in nitrogen. For me it is well worth the additional level of confidence.

cheers

 

[Zutroy]

Air is fine as it was stated the main reason is it's cheap to get a cylinder of it, and it's 0% water. It ill also be leak slower and air slight and will every to slightly be less prone to temp changes. Later reason is why they use nitrogen in tires for racing these days.

 

[vitox]

Hmmm, Well what most forget about with Nitrogen and air is taht Nitrogen in a shock is used to stailize the oil from foaming. Some shocks are Assembled using oils that dont need that to keep it from happening. WHile others use a Nitrogen charge over the Oil, and have a bladder for an air chamber so you can customise your feel better. The whole Nitrogen charged shock idea on Mtn bikes started with Auto's. Your gas shocks on your cars/trucks are Nitrogen charged to stabilize the oil from foaming, hence eliminating fade. doesnt take alot to do it either.

hey thats a good point too, point in favor of using nitrogen if you have an "emulsion" shock but to my knowledge there are no such shocks in bikes.

 

[vitox]

Hey Vitox,

I know your a suspension guru and appreciate your feedback. FYI my handle has nothing to do with my riding ability. Ever seen someone called Tiny?

Anyway the shock for sure seriously over heated. I agree it is unlikely to over heat to the point I discribed but I attribute it to the fact the shim stack at the time was likely not bending at all and at 220lbs with out gear it was taxed more than normal. The plastic ring on the banjo was visably distorted from heat but it did not leak. I had to change out the pistion/shaft seal as well.

Once tuned properly and charged with nitrogen it worked awesome. The guy who worked on my shock (two trick racing) tunes factory motorcycle suspension for a living and learned his trade from a former world GP suspension tuner. He was not surprised at all. I am sure air works fine 99% of the time but for 10bux I would just put in nitrogen. For me it is well worth the additional level of confidence.

cheers

wow that thing seriously was just about to kick the bucket as you yanks say. never seen anything like it, glad you got it worked out just with valving and nitro charge.
weird thing however is that you are pretty heavy and you say the shims werent working properly, did that valving come stock that way?

 

[SCABRIDER]

nitrogen is what should be used...

 

[DirtyMike]

hey thats a good point too, point in favor of using nitrogen if you have an "emulsion" shock but to my knowledge there are no such shocks in bikes.

Unless its an Elestomer shock, they all work the same way. a cylender, a valve<Or more> and oil. The nitrogens works so well as teh stabilzer for a couple reason's. first off, The purity. You can better account for what is going to happen. second, its readily available. third, it doesnt leak out like "air" does. with our Atmosphere as high in concetration of Nitrogen as it is you also see it doesnt change pressure on its own from heat, altitude etc like O2 would.... ANywho just some more info on it

 

[vitox]

Unless its an Elestomer shock, they all work the same way. a cylender, a valve<Or more> and oil. The nitrogens works so well as teh stabilzer for a couple reason's. first off, The purity. You can better account for what is going to happen. second, its readily available. third, it doesnt leak out like "air" does. with our Atmosphere as high in concetration of Nitrogen as it is you also see it doesnt change pressure on its own from heat, altitude etc like O2 would.... ANywho just some more info on it

no, with "emulsion" type shock i meant a particular form of design where the pressurizing gas comes in direct contact with the suspension oil, that means, no bladder, no floating piston and probably no good for any mountain bike type application, but in that case i could see how using a pressurizing agent that had the best possible anti-foaming characteristics.