What air pressure in Fox airshocks

[eric318]

"Oxygen behaves differently to air, compressed air, nitrogen and other inert gases. It is very reactive. Pure oxygen, at high pressure, such as from a cylinder, can react violently with common materials such as oil and grease."
www.hse.gov.uk/pubns/hse8.pdf

Oxygen under high pressure 500-3000 psi is a very different beast from air at low pressure (like our shocks), 300 psi max.

 But hey, enjoy Nitrogen if you wish

[motomaniac]

Actually, I believe so, mostly. More a marketing trick than a real improvement, in my view, at least from what I can see when I do the maths (PV=nRT yadhayadha) with what is left of my physics knowledge. In truth, when I do the maths, there is a difference, but so small that it is unlikely to actually make a significant difference. But hey, I am far from being an expert in anything....

Some put a wing on the trunk of their car and they swear it makes them go faster No offense meant.

I have a pair of Fox Airshox to rebuild, cant wait to get to that part.

As for oil and oxygen being an explosive mixture, hmm, there is some truth in that but it seems to me not really applicable to our use cases.


I seem to remember that this is derived from the physics of the diesel engine (but will not ignite without a source of intense heat...) or the absolute necessity to never apply grease to the threads of compressed oxygen cylinders (memory from veterinary school many years ago). Thankfully the pressure in our shocks or forks can never reach the levels of compressed cylinders, by a long shot...

But hey, again... I am far from being an expert in anything....

What have you been smoking?

[JohnnyO]

I did a little research on why nitrogen is better than air..
Unlike air, nitrogen does not retain moisture and thus is not susceptible to sudden changes in temperature which can cause a change in pressure.
Typically a shock pressurised at 140lbs with air can increase to as much as 160lbs at the end of a moto where as nitrogen would only increase around 5lbs. That is a fair increase in airshocks when air is the spring.

[motomaniac]

I did a little research on why nitrogen is better than air..
Unlike air, nitrogen does not retain moisture and thus is not susceptible to sudden changes in temperature which can cause a change in pressure.
Typically a shock pressurised at 140lbs with air can increase to as much as 160lbs at the end of a moto where as nitrogen would only increase around 5lbs. That is a fair increase in airshocks when air is the spring.

plus moisture (water) is abrasive and will wear out your shock

[mainline]

How about we quit the aggro, there's been half a dozen conflicting versions of fact and various poor descriptions in this one short thread already. How about explaining upper and lower chambers vs high and low pressure.

Happy new year, we're talking about 35+ yr old dirt? bike shocks not the latest cancer treatments.

[JohnnyO]

How about we quit the aggro, there's been half a dozen conflicting versions of fact and various poor descriptions in this one short thread already. How about explaining upper and lower chambers vs high and low pressure.

Happy new year, we're talking about 35+ yr old dirt bike shocks. Lighten up, we're talking about 35-ish yr old dirt bike shocks not the latest cancer treatments.

Are you the new moderator? You're gunna be fukn busy!

[mainline]

[quote  ;Dauthor=JohnnyO link=topic=27130.msg264724#msg264724 date=1357893936]

How about we quit the aggro, there's been half a dozen conflicting versions of fact and various poor descriptions in this one short thread already. How about explaining upper and lower chambers vs high and low pressure.

Happy new year, we're talking about 35+ yr old dirt bike shocks. Lighten up, we're talking about 35-ish yr old dirt bike shocks not the latest cancer treatments.

Are you the new moderator? You're gunna be fukn busy!
[/quote]

No chance of that, I reckon half the shitfights on here are overdue. 

[NSR]

Unlike air, nitrogen does not retain moisture and thus is not susceptible to sudden changes in temperature which can cause a change in pressure.

Thats what I was going to say.  Use Nitrogen It's dry, clean and stable.

[crs-and-rms]

ok lower chamber hight pressure in bladder no oil unless blader has hole. upper chamber oil and lower pressure =emulsion  means no piston or blader seperating oil from air, allways  have bike on stand  [wheel off ground]  adjust high pressure 1st this is the lower chamber [shaft end] then adjust low pressure upper valve  . things you have to know  1 what bike weighs 2 what you weigh with riding gear 3 what the bikes suspension lever ratio   rear wheel travel divided by shock shaft travel = SLR . johnnyo is right about the air versus nitrogen  air expands more with heat and the mosture rusts parts anything else you want to know just ask i have two bikes with these shocks

[flower pot racing]

and when you hav decided what you ar going to do, vmxoutlet have got all the parts you require!  Check them out, they have lovely kit!

[eric318]

I did a little research on why nitrogen is better than air..
Unlike air, nitrogen does not retain moisture and thus is not susceptible to sudden changes in temperature which can cause a change in pressure.
Typically a shock pressurised at 140lbs with air can increase to as much as 160lbs at the end of a moto where as nitrogen would only increase around 5lbs. That is a fair increase in airshocks when air is the spring.

Numbers great! This is where the truth is to be found

I would love to see the math. Seriously.

The Specific Heat and Gas Constant values for Nitrogen (N2) and Oxygen (O2) are different (see here: http://www.engineeringtoolbox.com/spesific-heat-capacity-gases-d_159.html) but not that much.
With 1/4 of an air volume being O2 and the rest being Nitrogen N2 (with small amounts of water vapor, unless you live on the west coast of Ireland), the differences in SH and GC are then 3/4 smaller even.
My guess-timate is that Pressure and Temperature of either gases in a shock absorber at work are likely to be quite similar (and possibly hard to detect without measuring equipment). For where I stand, right now, Nitrogen or Air seems to be a personal choice, but that is just me.

But I would love to see the math, or actual measurements (like temperature of the shock at the end of a race, one with air, one with Nitrogen), seriously. But won't loose sleep over it

I also hear that Nitrogen is better for tires... oh rats, here is another conversation coming

Here is a good chat about this: http://www.thumpertalk.com/topic/936969-shock-pressure-nitro-vs-air/
I suggest you red those that show actual numbers...

[JohnnyO]

I did a little research on why nitrogen is better than air..
Unlike air, nitrogen does not retain moisture and thus is not susceptible to sudden changes in temperature which can cause a change in pressure.
Typically a shock pressurised at 140lbs with air can increase to as much as 160lbs at the end of a moto where as nitrogen would only increase around 5lbs. That is a fair increase in airshocks when air is the spring.

Numbers great! This is where the truth is to be found

I would love to see the math. Seriously.

The Specific Heat and Gas Constant values for Nitrogen (N2) and Oxygen (O2) are different (see here: http://www.engineeringtoolbox.com/spesific-heat-capacity-gases-d_159.html) but not that much.
With 1/4 of an air volume being O2 and the rest being Nitrogen N2 (with small amounts of water vapor, unless you live on the west coast of Ireland), the differences in SH and GC are then 3/4 smaller even.
My guess-timate is that Pressure and Temperature of either gases in a shock absorber at work are likely to be quite similar (and possibly hard to detect without measuring equipment). For where I stand, right now, Nitrogen or Air seems to be a personal choice, but that is just me.

But I would love to see the math, or actual measurements (like temperature of the shock at the end of a race, one with air, one with Nitrogen), seriously. But won't loose sleep over it

I also hear that Nitrogen is better for tires... oh rats, here is another conversation coming

Here is a good chat about this: http://www.thumpertalk.com/topic/936969-shock-pressure-nitro-vs-air/
I suggest you red those that show actual numbers...

You should be running one of the big shock companies because they've obviously forked up using nitrogen. The stuff i quoted was straight from a shock manufacturers website.
You keep using air and i'll stick to nitrogen thanks..

[motomaniac]

[/quote]
Numbers great! This is where the truth is to be found

I would love to see the math. Seriously.

 Nitrogen or Air seems to be a personal choice, but that is just me.

But I would love to see the math, or actual measurements (like temperature of the shock at the end of a race, one with air, one with Nitrogen), seriously. But won't loose sleep over it
I also hear that Nitrogen is better for tires... oh rats, here is another conversation coming
I suggest you red those that show actual numbers...
[/quote]You should be running one of the big shock companies because they've obviously forked up using nitrogen. The stuff i quoted was straight from a shock manufacturers website.
You keep using air and i'll stick to nitrogen thanks..

[/quote]
Yer he could be running a SX or GP team , imagine the budget savings not having to lug those silly nitrogen bottles around.If only Moose knew he could have had a bigger BBQ gas bottle installed in the Ohlins truck where the silly n2 bottle was. Now theres an idea ! How about BBQ gas , everyone s got one of those. Geez 

[Snowy 76]

Yeah, Makes you talk funny!!

[270YAM]

Anyone tried Helium ?

Helium helps you jump further!!