Armed Polite Society
Main Forums => The Roundtable => Topic started by: Fly320s on December 20, 2011, 10:45:18 AM
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What says the hive?
A local oil change place was having a deal on nitrogen-fill, so I gave it a try. Of course now I have to go to them or other special places to get the air checked and topped as needed. I did this two months ago and the tires look to be holding pressure well, but I don't really want to check them because then I have to pay to get the N2 topped off.
Anyone run N2 in their tires? Worth it? Waste of money?
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On a street car, I don't really see the point.
What's the advantage?
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On a street car, I don't really see the point.
What's the advantage?
This
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I use a special blend with 78% Nitrogen, instead of 100%. =D
Okay... okay... I keed. But someone has to say it every time a "N2" in tires? thread comes up.
In theory, the other 20% of lighter Oxygen could leak out faster, and there's a certain percentage of water vapor in an atmospheric compressor's source. While collected N2 is 'dry' etc. And it has a different/better expansion coefficient when heated/cooled meaning tire pressure will vary less.
So yes, it's "better", however, it's rare that it's X amount "better" as compared to the price you pay for an N2 fill, and the increased life of the tire due to it deflating more slowly, and not oxidizing on the inside as much due to no O2 or moisture being in there.
I'm skeptical. I suspect that N2 fills alone probably extend the life of your tire by a few months, statistically speaking. I'd only do it if it was free, or the same price as a for-pay air-compressor, like $.50 etc.
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I know a lot of race cars use N2 instead of normal air. Main reason is the non-N2 components of air (ar is ~79% N2, ~19%O2, ~2% misc.) have a much higher coefficient of thermal expansion, so there's less of a difference in tire pressure between cold and hot conditions.
On a street car, driven by a (more or less) normal person? You'll probably never notice a difference. I'd say it's not worth the expense.
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That's crazy! What if it blows up?! :O ;)
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you can convince a weight weenie triathlon bike dork that a He fill will lighten his bicycle
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In theory, the other 20% of lighter Oxygen could leak out faster, and there's a certain percentage of water vapor in an atmospheric compressor's source. While collected N2 is 'dry' etc. And it has a different/better expansion coefficient when heated/cooled meaning tire pressure will vary less.
This is always the sell. I contend that anyone who is driving there car to those limits on the street where such a minor change would matter has no business driving on the street. Pushing a passenger car to it's performance limit in an uncontrolled environment is extremely hazardous for both the driver and everyone else on the road.
The other sell I hear on the internet has to do with it "not oxidizing the rubber, so the tires last longer" or "if you have a blowout, it won't catch on fire". I dismiss both these arguments as irreverent to street driving as well.
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irreverent to street driving as well
I didn't know street driving was deserving of reverence. ;)
The supposed benefits above--temperature consistency, less leakage--are benefits to race drivers, who are trying to exact every last 1/100th of performance from their cars. Once you get past basic modifications to fuel delivery (carbs, fuel injection, blower), cams and exhaust, the cost per horsepower realized increases dramatically.
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people like numbers and factoids that make them seem cool and smarter
you really don't need a quad core i7 to run farmville in facebook
and you don't need special mixtures in your car tires
but PT Barnum will profit from selling them
OMG the new iphone has a 87 megapixel imager!!!!!!
In some regards, the Amish are a lot more sane
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you can convince a weight weenie triathlon bike dork that a He fill will lighten his bicycle
Quit doing stuff like that to mtnbkr. He's a nice guy, bless his heart.
Save that stuff for Jamis.
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I sense a trend here. ;)
So, can I top-off with regular compressed air as needed then?
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you can convince a weight weenie triathlon bike dork that a He fill will lighten his bicycle
A hydrogen fill would be even lighter, but it's still in 2nd place behind a vacuum fill.
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He
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I sense a trend here. ;)
So, can I top-off with regular compressed air as needed then?
No, that would contaminate the pure nitrogen.
Let all the nitrogen out first, and then inflate to recommended pressure with compressed air.
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Ha ha.
My Nissan Truck came with nitrogen in the tires.
I have noticed that it is the only vehicle we have (1 of 6) that the tire pressure light doesn't come on in when the weather changes...or maybe the lights broke.
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He's a nice guy, bless his heart.
I don't know how the phrase "bless his (or her) heart" is used in Missouri, but here in AL it seems to be a polite way of saying "what an idiot".
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I don't know how the phrase "bless his (or her) heart" is used in Missouri, but here in AL it seems to be a polite way of saying "what an idiot".
Same thing.
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What says the hive?
Load of crap
A local oil change place was having a deal on nitrogen-fill, so I gave it a try.
Hope it was free
Of course now I have to go to them or other special places to get the air checked and topped as needed.
No you do NOT and if someone told you that, kick him in the toodles
I did this two months ago and the tires look to be holding pressure well, but I don't really want to check them because then I have to pay to get the N2 topped off.
No you don't, and sounds like it wasn't free.
Anyone run N2 in their tires? Worth it? Waste of money?
No. No. Yes.
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Ever ask one of the A&P guys[gals] what they run in the tires on your "bus" ?
:lol:
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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.
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Ever ask one of the A&P guys[gals] what they run in the tires on your "bus" ?
:lol:
N2.
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N2.
Well then maybe you should go with that if you are going to be doing Evil Knievel stuff :lol:
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.
Yeah, except for flats from driving on gravel roads =(
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Air is only 78% nitrogen, so I use plain air, but overfill my tires by about 20% to get the same amount of nitrogen in them.
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Air is only 78% nitrogen, so I use plain air, but overfill my tires by about 20% to get the same amount of nitrogen in them.
And then after a while the oxygen will all leak out :lol:
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And then after a while the oxygen will all leak out :lol:
So how do your tires breathe?! ???
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So how do your tires breathe?! ???
I'm going to fill them with NO2 and see if they start laughing =D
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If you fill the tires with nitrogen instead of air, oxygen will leak *in* and keep the pressure up for a while. ;/
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I don't know how the phrase "bless his (or her) heart" is used in Missouri, but here in AL it seems to be a polite way of saying "what an idiot".
I thought it was pretty much universal.
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I don't know how the phrase "bless his (or her) heart" is used in Missouri, but here in AL it seems to be a polite way of saying "what an idiot".
I was trying to be nice about it. You don't have to just come out and say it.
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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.
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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.
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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.
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N2.
Then clearly that's what you'll need when you start driving your car from 0 to 35,000 feet.
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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
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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.
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Figure roughly 1 psi difference per 10 deg F of temp change.
C maybe
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C maybe
Then wouldn't the pressure be in Pa?
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C maybe
Nope, farenheit. That's for an average passenger car tire, though. Bike tires? I've no idea.
Brad
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Why not hydrogen?.....there's a lot more of it in the universe, so it'll probably be cheaper....
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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.
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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
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I've got this $200 noisemaker out in the garage that works pretty well ;)
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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.
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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 :'(
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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.
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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
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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 :O
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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?
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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...
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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?
While that might be interesting from "too much time on his hands academic" point of view, it would have no real-life appreciable effect. The mass of air in the tire, assuming 70F, 30psig (45psia), an 18" interior OD, 15" interior ID, and 8" width is only 0.08lbs.
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I'm just amazed that back in the dark ages of the 20th century we managed to get along with just plain old compressed air in our tires. ;/
I can even remember using organic air from a hand pump :P
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Tallpine, you had it easy. We had to make our own.
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While that might be interesting from "too much time on his hands academic" point of view, it would have no real-life appreciable effect. The mass of air in the tire, assuming 70F, 30psig (45psia), an 18" interior OD, 15" interior ID, and 8" width is only 0.08lbs.
That's a small low profile tire...it would be a 205/18-15! A more typical (but still low profile) 205/50-15 would have about 1/3rd of a pound--still inconsequential, but more reasonable
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Tallpine, you had it easy. We had to make our own.
That really blows =(
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Just be careful with the N2. Tweakers like to suck it out of your tires to get high.
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I imagine that whole explosive/flammable thing might be a reason.
What's the worst that could happen?.....
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That's a small low profile tire...it would be a 205/18-15! A more typical (but still low profile) 205/50-15 would have about 1/3rd of a pound--still inconsequential, but more reasonable
It's unsprung weight, and it's in the wheel, but at the same time it's not exactly rotational weight either because the air isn't going to rotationally accelerate right along with the wheel and tire, it'll lag behind. Like when you rotate a drinking glass and the ice and water inside don't really move.
But, for sake of argument, lets assume the air mass is actually locked to the wheel and rubbber:
A fun math exercise would be to take the 1/3 lb, treat it as a evenly-distributed torroidal mass that its inside the center of the airspace of the tire, and measure how much power would be required to accelerate it up to whatever wheel RPM you have at the end of your best 1/4 mile run, in a time window equivalent to your ET for that run. Go ahead and add in the linear acceleration along the track for a true worst-case scenario.
If you figure that out, I would love to know what X is in the statement "During my best 1/4 mile run in the Skyline, X horsepower was used just to accelerate the air in the tires."
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Math is still looking for his Ex :lol:
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It's unsprung weight, and it's in the wheel, but at the same time it's not exactly rotational weight either because the air isn't going to rotationally accelerate right along with the wheel and tire, it'll lag behind. Like when you rotate a drinking glass and the ice and water inside don't really move.
But, for sake of argument, lets assume the air mass is actually locked to the wheel and rubbber:
A fun math exercise would be to take the 1/3 lb, treat it as a evenly-distributed torroidal mass that its inside the center of the airspace of the tire, and measure how much power would be required to accelerate it up to whatever wheel RPM you have at the end of your best 1/4 mile run, in a time window equivalent to your ET for that run. Go ahead and add in the linear acceleration along the track for a true worst-case scenario.
If you figure that out, I would love to know what X is in the statement "During my best 1/4 mile run in the Skyline, X horsepower was used just to accelerate the air in the tires."
Well...given the tires average to a 275/30-20 at 28psi, it's roughly 220g per tire so two pounds for all four...car with me in it is 4000. For tire air (which will be at rotating speed with effectively no lag to answer that question) effective inertia (rotating plus static) is twice static, so 4 lbs effective, so it took 1/1000th of the power just to accelerate the air, or about 0.5HP.
To put in perspective, that's about the same as the air resistance of a cyclist at 40, just to accelerate the air!
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The whole nitrogen scam reminds me of the time several years ago a tractor dealer down here sold the state a fleet of tractors that were a brand that used property grease fittings (which would have taken a $6 grease gun adapter to service). The dealer was able to convince the state people that the tractors HAD to be greased at the dealership and was able to charge big bucks to go get the tractors with a lowboy, take them back to the shop, and grease them and return.
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Just to clarify:
Nitrogen for a normal car = scam
Nitrogen for race car = not scam
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It's a load of crap and a way to separate fools from their money.
Russ
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Again, for normal cars, yes.
But to use the F1 argument,
Since there is no rule or argument mandating a pure N2 fill for tires, they wouldn't use it unless there was a performance advantage.
Since you are unwilling to accept all the reasons so far, do you have a reason other than a scam, why, when performance at any cost is the goal, nitrogen is chosen for race cars?
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I don't drive a race car as my daily driver. Yes, there are performance advantages when you are talking speeds well in excess of our interstate speeds. I also don't wear a helmet or a 5 pt harness in my car, nor do I have a roll cage. Apples to oranges.
For our daily drivers, it's a scam, pure and simple.