Nose loses PSI faster than mains

I always thought more oxygen was better and I used my nitrox tanks to fill the tires.
/s
 
ArrowFlyer86 said:
Thanks guys. I'll use soapy water and see if there's anything noticeable.

I'm using compressed air not n2 for the tires.
A few months ago I looked at getting a nitro bottle from airgas so I could use N2 (and so I could add to my struts, when needed). But with the tank cost, the regulator, the adapter to actually fill up the tires... Juice wasn't worth the squeeze on that one. I think it was like $600 for the most basic solution. Compare that to a $50 air compressor :)
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No way it should cost that much. Get an 80 cubic foot nitrogen tank for 140 bucks. 35 dollar Amazon regulator. Air hose quick couple. Done.
 
Racerx said:
No way it should cost that much. Get an 80 cubic foot nitrogen tank for 140 bucks. 35 dollar Amazon regulator. Air hose quick couple. Done.
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I only inquired with the fine folks at Airgas about pricing. Didn't look around any further.
They essentially said the tank was going to be $X (I wanna say 300ish?), and then said you can get a cheaper tank, but Airgas wont fill/exchange them.
 
Check with who does hydro test on hi pressure cylinders in your area. I bought my tanks from them. They were not new, the valves were and came with a fresh test. Then the local gas supply filled them to begin with. They are right up the street from the tester.
 
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On my 172 I am able to add N2 to my front strut and all 3 tires with this straight truck chuck.
The angle one works good for bike tires.
front strut get's adjusted by bleeding gas until I get the right ride height right. I recently lost 50 lbs off of my frame, now I need less in the front strut.
I have wheel pants, I screw a valve stem extender onto the valve stem through access hole in the wheels pants. Then it is easy to refill the tires. Always bleed them down to the correct pressure. Remove plastic extender and there is no air loss.
The tires gets checked with a milton stab gauge from a auto parts store.
b9992e07-4b7e-4241-81e6-5ad222e32569.jpg
 
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Craig said:
Arrow: How did your experiment come out?
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Good question!
I checked the air 2 days after and the nose showed 0.5 PSI lower, which didn't set off any alarm bells.
It's been another 8 days now so I'm due to go back and check! Will letcha know what it looks like.
 
ArrowFlyer86 said:
Took a new measurement. It came in 1 PSI lower than the pressure reading 9 days ago. That's measured inside heated hangar at ~same temp both times.
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Is that slower than previously?
 
Domenick said:
According to WebElements, O2 (double bonded) is slightly bigger than N2 (triple bonded).
There are multiple ways to determine molecular size. Remember, these are oblong so they have two axes. The numbers below are the long axis, and I believe pm is pico-meters.
N2 109.76 pm
O2 120.74 pm

There are other ways to measure molecular size. All seem to show O2 slightly larger than N2.

HOWEVER, at these scales molecular size is irrelevant. Size is not the only determinant of permeability. Reactivity is a bigger factor. The operative characteristic of whether N2 or air leaks faster through the tire material is specific permeability of the gas through the material.

WebElements Periodic Table » Oxygen » radii of atoms and ions

www.webelements.com www.webelements.com

WebElements Periodic Table » Nitrogen » radii of atoms and ions

www.webelements.com www.webelements.com

I leave permeability as a search exercise for others.
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Were talking rubber tires here... O2 seeps out faster than N2. Why? N2 is larger. So when talking about compressed atmospheric air vs N2 gas 'air' has more of the smaller 02 molecules that seep out faster.
 
pfarber said:
Were talking rubber tires here... O2 seeps out faster than N2. Why? N2 is larger. So when talking about compressed atmospheric air vs N2 gas 'air' has more of the smaller 02 molecules that seep out faster.
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Read the post you quote. Molecular nitrogen (N2) is slightly SMALLER than molecular oxygen (O2). Despite this, it appears N2 has a higher diffusion rate through rubber.
 
Arrow: 1 psig in 9-10 days, for the tube compounds we get these days is what I would call an acceptable loss rate.
 
One fun point to discuss with N2 devotees...

Assume your standard compressor will fill the tire with 78% N2 and 21% O2. Let's just make it 80/20 for simplicity sake.

The pro N2 crowd claim its beneficial to buy N2 because O2 diffuses through the rubber quicker than the N2.

With that assumption, every time we re-fill with compressed air, 80% of the lost O2 is replaced with N2.

It doesn't take too many compressed air re-fill cycles with that math until the tire is left with nearly 100% N2 in the tube.

So, all tires without leaks that lose pressure via 02 diffusion will eventually become N2 filled, regardless of the source, right??
 
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ElPaso Pilot said:
One fun point to discuss with N2 devotees...

Assume your standard compressor will fill the tire with 78% N2 and 21% O2. Let's just make it 80/20 for simplicity sake.

The pro N2 crown claim its beneficial to buy N2 because O2 diffuses through the rubber quicker than the N2.

With that assumption, every time we re-fill with compressed air, 80% of the lost O2 is replaced with N2.

It doesn't take too many compressed air re-fill cycles with that math until the tire is left with nearly 100% N2 in the tube.

So, all tires without leaks that lose pressure via 02 diffusion will eventually become N2 filled, regardless of the source, right??
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Kinda suggests something else is going on, doesn't it? :)
 
Unless you have a real good dryer on your compressor, you are also putting a great deal of H2O in that tire too. Most all the airlines use N2 because it's also drier. Therefore less pressure change with temperature changes.
 
ElPaso Pilot said:
One fun point to discuss with N2 devotees...

Assume your standard compressor will fill the tire with 78% N2 and 21% O2. Let's just make it 80/20 for simplicity sake.

The pro N2 crowd claim its beneficial to buy N2 because O2 diffuses through the rubber quicker than the N2.

With that assumption, every time we re-fill with compressed air, 80% of the lost O2 is replaced with N2.

It doesn't take too many compressed air re-fill cycles with that math until the tire is left with nearly 100% N2 in the tube.

So, all tires without leaks that lose pressure via 02 diffusion will eventually become N2 filled, regardless of the source, right??
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Also, if you fill with air to 28 psi and subsequently lose all the O2, the pressure should stabilize around 22.4 psi.
Personally, I don't give it a second thought--air in tires and struts.

Sacrilege!!
 
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