Author Topic: Nitrogen in tires, instead of air. (Read 7129 times)

The advantage is that your tire pressure will stay consistent between oil changes. I check mine every so often on my truck, especially after wild temperature swings, yet it never changes.

But, is that due to the moisture or the O2 in normal compressed air?

My company has an air separation plant selling oxygen to a mine over in Nevada. They use the nitrogen to fill the tires of the big mine trucks whose tires are very very big and I imagine very expensive. The nitrogen would be vented if not used for something.

Azrael256 · « **Reply #31 on:** December 20, 2011, 08:15:30 PM »

Quote

What says the hive?

Scam to sell tires and maybe service.

I can invalidate your warranty on the tires for filling them with air as long as I provide free nitrogen.

If you can come up with a *Measurable* benefit in a road car, I will eat my boots. This means a measurable improvement of some kind that is outside the margin of error in fuel mileage, tire longevity, safety, etc., not some pointless anecdote about B-52s, space shuttles, or what your cousin said.

Nobody has taken me up on this yet.

Jamisjockey · « **Reply #32 on:** December 20, 2011, 08:51:18 PM »

Quote from: MechAg94 on December 20, 2011, 06:20:25 PM

But, is that due to the moisture or the O2 in normal compressed air?

My company has an air separation plant selling oxygen to a mine over in Nevada. They use the nitrogen to fill the tires of the big mine trucks whose tires are very very big and I imagine very expensive. The nitrogen would be vented if not used for something.

Beats me why, but it works.
I've got regular air in the boat trailer tires and lost about 8 PSI after the first cold front of the season.

KD5NRH · « **Reply #33 on:** December 20, 2011, 10:01:34 PM »

Quote from: Fly320s on December 20, 2011, 02:55:24 PM

N2.

Then clearly that's what you'll need when you start driving your car from 0 to 35,000 feet.

Brad Johnson · « **Reply #34 on:** December 20, 2011, 10:05:09 PM »

Quote from: JamisJockey on December 20, 2011, 08:51:18 PM

Beats me why, but it works.
I've got regular air in the boat trailer tires and lost about 8 PSI after the first cold front of the season.

Figure roughly 1 psi difference per 10 deg F of temp change.

Brad

Monkeyleg · « **Reply #35 on:** December 20, 2011, 11:04:48 PM »

My cycle has a pretty narrow front tire, and changes pressure substantially with temperature. In cold weather it will be in the 20+ pound range, and in really hot weather it will be pushing 50 psi after sitting all night. When I'd tell that to riders from WI, they wouldn't believe me.

CNYCacher · « **Reply #36 on:** December 20, 2011, 11:37:52 PM »

Quote from: Brad Johnson on December 20, 2011, 10:05:09 PM

Figure roughly 1 psi difference per 10 deg F of temp change.

C maybe

KD5NRH · « **Reply #37 on:** December 21, 2011, 12:20:58 AM »

Quote from: CNYCacher on December 20, 2011, 11:37:52 PM

C maybe

Then wouldn't the pressure be in Pa?

Brad Johnson · « **Reply #38 on:** December 21, 2011, 12:40:57 AM »

Quote from: CNYCacher on December 20, 2011, 11:37:52 PM

C maybe

Nope, farenheit. That's for an average passenger car tire, though. Bike tires? I've no idea.

Brad

seeker_two · « **Reply #39 on:** December 21, 2011, 12:48:14 AM »

Why not hydrogen?.....there's a lot more of it in the universe, so it'll probably be cheaper....

Fly320s · « **Reply #40 on:** December 21, 2011, 01:01:04 AM »

Quote from: seeker_two on December 21, 2011, 12:48:14 AM

Why not hydrogen?.....there's a lot more of it in the universe, so it'll probably be cheaper....

I imagine that whole explosive/flammable thing might be a reason.

CNYCacher · « **Reply #41 on:** December 21, 2011, 01:54:22 AM »

Quote from: Brad Johnson on December 21, 2011, 12:40:57 AM

Nope, farenheit. That's for an average passenger car tire, though. Bike tires? I've no idea.

Agreed. I was doing rough math too roughly in my head.

To be more precise:

80 degrees Fahrenheit is very close to 300 kelvin
70 degrees Fahrenheit is very close to 294 kelvin

The difference of 6 degrees kelvin represents a 2% shift towards absolute zero

The absolute pressure in a standard tire is about 50psi relative to vacuum, assuming 35 psi relative to atmosphere and for our purposes 15psi atmosphere is close enough.
A drop of 1 PSI from 50 to 49 is indeed a 2% drop.

You sir, are absolutely correct. Great rule of thumb to remember

Tallpine · « **Reply #42 on:** December 21, 2011, 09:24:09 AM »

I've got this $200 noisemaker out in the garage that works pretty well

birdman · « **Reply #43 on:** December 21, 2011, 09:30:16 AM »

Already discussed (and I didn't want to re-write all my technical responses)
http://www.armedpolitesociety.com/index.php?topic=31285.0

Btw, I run nitrogen.

zxcvbob · « **Reply #44 on:** December 21, 2011, 09:45:00 AM »

Quote from: birdman on December 21, 2011, 09:30:16 AM

Already discussed (and I didn't want to re-write all my technical responses)
http://www.armedpolitesociety.com/index.php?topic=31285.0

Btw, I run nitrogen.

Nobody ever addressed my "partial pressures" theory

birdman · « **Reply #45 on:** December 21, 2011, 10:59:20 AM »

Quote from: zxcvbob on December 20, 2011, 05:46:49 PM

If you fill the tires with nitrogen instead of air, oxygen will leak *in* and keep the pressure up for a while.

Technically yes, but only up to 0.21 atmospheres of o2, or an addition of about 3psi gauge. However, oxygen is a larger (and more reactive) molecule than nitrogen, and given the great dP of the nitrogen to the outside, the nitrogen leak rate out will far exceed the oxygen leak rate in. Even if they had similar diffusion values, the rate of nitrogen loss will exceed the rate of oxygen ingress by a factor of 5-10, so the tire will always lose pressure.

Brad Johnson · « **Reply #46 on:** December 21, 2011, 12:03:22 PM »

Cost of driving 3 miles to get a "free top off" of nitrogen in a vehicle that gets an average 25 mpg, and with gas prices at $3 per gallon - 85 cents. That includes wear on tires and the additional miles towards an oil change. I did not factor in a mileage depreciation.

Cost of topping off the tires in the convenience of my own garage using household electricity at $0.10/KwH - eight tenths of a cent ($0.008). That does not include the Scooby Doo pj's, the fuzzy slippers, or the ugly hat I wear to give the neighbors something to talk about.

Brad

Tallpine · « **Reply #47 on:** December 21, 2011, 12:17:59 PM »

Quote from: Brad Johnson on December 21, 2011, 12:03:22 PM

Cost of driving 3 miles to get a "free top off" of nitrogen in a vehicle that gets an average 25 mpg, and with gas prices at $3 per gallon - 85 cents. That includes wear on tires and the additional miles towards an oil change. I did not factor in a mileage depreciation.

Cost of topping off the tires in the convenience of my own garage using household electricity at $0.10/KwH - eight tenths of a cent ($0.008). That does not include the Scooby Doo pj's, the fuzzy slippers, or the ugly hat I wear to give the neighbors something to talk about.

Brad

Plus, if you have a flat that pure nitrogen gets released into the atmosphere, displacing the oxygen and contributing to Global Fear Mongering

Sindawe · « **Reply #48 on:** December 21, 2011, 09:49:41 PM »

All this talk of nitrogen fill vs. compressed air fill; how much the internal pressure of the filled tires varies with the change in ambiant temperature; final cost analysis of driving to a specialized N2 fill station vs. the corner gas station compressed air for a top off is all well and truely fascinating.

What I really want to know is how the air (or pure nitrogen) fill in the tire moves over time as the tire travels down the road.

Air has mass, so intertia must come into play as the tire starts to rotate in travel. I can see the fill right next to the tire and the wheel being dragged along for the ride (so to speak) with the tire and wheel and and the wheel, but what about the air further away from the rotating surfaces? How long does it take for that fill to come to a rotational equilibrium with the rest of the rotating body, and how long does it take to come to rest when the tire stops moving?

What about when the vehicle changes its rate of movement in stop and go events? Does the density of the fill change over a unit area as the tire comes to a stop or starts from a stop?

Nick1911 · « **Reply #49 on:** December 21, 2011, 10:04:49 PM »

Quote from: Sindawe on December 21, 2011, 09:49:41 PM

All this talk of nitrogen fill vs. compressed air fill; how much the internal pressure of the filled tires varies with the change in ambiant temperature; final cost analysis of driving to a specialized N2 fill station vs. the corner gas station compressed air for a top off is all well and truely fascinating.

What I really want to know is how the air (or pure nitrogen) fill in the tire moves over time as the tire travels down the road.

Air has mass, so intertia must come into play as the tire starts to rotate in travel. I can see the fill right next to the tire and the wheel being dragged along for the ride (so to speak) with the tire and wheel and and the wheel, but what about the air further away from the rotating surfaces? How long does it take for that fill to come to a rotational equilibrium with the rest of the rotating body, and how long does it take to come to rest when the tire stops moving?

What about when the vehicle changes its rate of movement in stop and go events? Does the density of the fill change over a unit area as the tire comes to a stop or starts from a stop?

Density of N2 = 28.02 kg/kmol
Density of O2 = 32 kg/kmol

Density of Air = 28.97 kg/kmol

I don't think there will much difference between air and pure N2 on this one...

News:

Author Topic: Nitrogen in tires, instead of air. (Read 7129 times)