Why do we run the same pressure winter and summer? Wouldn't it work to put the tires at say 35 psi on a 70 degree day, and assuming no leakage, if they went to 28 on a 20 degree day, why pump them up? Once you start drivng they will warm and when they warm to 70 degrees they should be at the specified 35 psi. Otherwise, by pumping them to 35 psi at 20 degrees, aren't they going to be overinflated by the time they warm to 70 degrees?
Tire Pressure--Stupid Question
- Thread starter TallPaul
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As far as I know, the placards refer to cold pressure. So, if one is in a heated garage or it's summer, they may have to release some air compared to say, when the vehicle was stored outside in -40.
My TPMS reflected that, too. I had the tires on the G set to 33 psi cold as required, but that was in my heated garage at 10 C. We had some blisteringly cold days, and it spent a bit of time outside, and the tires obviously got cold, and that kicked off the TPMS warning.
My TPMS reflected that, too. I had the tires on the G set to 33 psi cold as required, but that was in my heated garage at 10 C. We had some blisteringly cold days, and it spent a bit of time outside, and the tires obviously got cold, and that kicked off the TPMS warning.
I think you're both right: what really matters is the running pressure, but that should be related to the running temperature, which depends on ambient temperature and road conditions (icy/snowy, wet, dry).
What I don't understand is only inflating the tires to the recommended pressure. In order to get even wear, wouldn't you want the average cold pressure to be the specified pressure? So if my tires lose 3 psi in 1000 miles, wouldn't I want to fill them to 1.5 psi over the recommendation?
What I don't understand is only inflating the tires to the recommended pressure. In order to get even wear, wouldn't you want the average cold pressure to be the specified pressure? So if my tires lose 3 psi in 1000 miles, wouldn't I want to fill them to 1.5 psi over the recommendation?
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As far as I know, the placards refer to cold pressure.
+1
Several years ago a better tire shop I patronized started promoting the use of pure nitrogen for tire inflation. Nitrogen expands/contracts less at any given temperature than using air alone. Some thought is was hype but I knew it wasn't. It will help increase tire longevity. Consistant pressure along with decreased tire temps. It's exactly why we used dry nitrogen in all military and commercial aviation tires. (Don't know if the general aviation folks utilize this).
I've seen cold tires sweat like crazy on the flightline after a commercial jet came down from an extended flight at altitude in the summer. Checked the pressure and it was right where it needed to be. I still use it in all my tires simply because there's almost no pressure varience hot/cold winter/summer.
As far as I know, the placards refer to cold pressure.
+1
Several years ago a better tire shop I patronized started promoting the use of pure nitrogen for tire inflation. Nitrogen expands/contracts less at any given temperature than using air alone. Some thought is was hype but I knew it wasn't. It will help increase tire longevity. Consistant pressure along with decreased tire temps. It's exactly why we used dry nitrogen in all military and commercial aviation tires. (Don't know if the general aviation folks utilize this).
I've seen cold tires sweat like crazy on the flightline after a commercial jet came down from an extended flight at altitude in the summer. Checked the pressure and it was right where it needed to be. I still use it in all my tires simply because there's almost no pressure varience hot/cold winter/summer.
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Toyota addressed this issue here:
http://www.toyotapart.com/TIRE_INFLATION_PRESSURE_COMPENSATION_AND_ADJUSTMENT_T-SB-0345-08.pdf
http://www.toyotapart.com/TIRE_INFLATION_PRESSURE_COMPENSATION_AND_ADJUSTMENT_T-SB-0345-08.pdf
Originally Posted By: jetmech1
....Several years ago a better tire shop I patronized started promoting the use of pure nitrogen for tire inflation. Nitrogen expands/contracts less at any given temperature than using air alone......
No, it doesn't - or at least, not enough to worry about.
Originally Posted By: jetmech1
....Some thought is was hype but I knew it wasn't......
I'm sorry, but it IS hype.
Originally Posted By: jetmech1
.... It will help increase tire longevity.....
That's entirely debateable.
Originally Posted By: jetmech1
....Consistant pressure along with decreased tire temps. It's exactly why we used dry nitrogen in all military and commercial aviation tires. (Don't know if the general aviation folks utilize this).....
Sorry, but the laws of physics do NOT support that statement. It's called the ideal gas law, and it applies to ALL gases, including mixtures, like air.
I find it very telling that not one - NOT ONE - tire manufacturer recommends using it. If they publish anything on the subject, it is a neutral position - in other words, they say it causes no problems. The ONLY people pushing nirogen are the folks who sell the equipment - and we know they aren't neutral on the subject!
If you want to argue about it, first read this:
http://www.barrystiretech.com/nitrogeninflation.html
....Several years ago a better tire shop I patronized started promoting the use of pure nitrogen for tire inflation. Nitrogen expands/contracts less at any given temperature than using air alone......
No, it doesn't - or at least, not enough to worry about.
Originally Posted By: jetmech1
....Some thought is was hype but I knew it wasn't......
I'm sorry, but it IS hype.
Originally Posted By: jetmech1
.... It will help increase tire longevity.....
That's entirely debateable.
Originally Posted By: jetmech1
....Consistant pressure along with decreased tire temps. It's exactly why we used dry nitrogen in all military and commercial aviation tires. (Don't know if the general aviation folks utilize this).....
Sorry, but the laws of physics do NOT support that statement. It's called the ideal gas law, and it applies to ALL gases, including mixtures, like air.
I find it very telling that not one - NOT ONE - tire manufacturer recommends using it. If they publish anything on the subject, it is a neutral position - in other words, they say it causes no problems. The ONLY people pushing nirogen are the folks who sell the equipment - and we know they aren't neutral on the subject!
If you want to argue about it, first read this:
http://www.barrystiretech.com/nitrogeninflation.html
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Not a stupid Q. Some vehicles don't handle well on over-inflated tires.
My Focus rides nice when I keep cold psi 2# lower than placard number.
My Focus rides nice when I keep cold psi 2# lower than placard number.
Originally Posted By: jetmech1
It's exactly why we used dry nitrogen in all military and commercial aviation tires. (Don't know if the general aviation folks utilize this).
The main reason nitrogen is used in aviation is because it's not fuel to a fire, like oxygen is.
It's exactly why we used dry nitrogen in all military and commercial aviation tires. (Don't know if the general aviation folks utilize this).
The main reason nitrogen is used in aviation is because it's not fuel to a fire, like oxygen is.
In aviation school we were taught to use nitrogen for four main reasons, in this order:
1. Reduction of water vapor, which means a more consistent tire pressure at all temperatures, especially during landing when water wapor will quickly expand, resulting in a sudden and potentially catastrophic increase in tire pressure
2. Nitrogen-only inflation will not add oxygen to a fire should the tire burst
3. Less corrosion of the wheel and breakdown of the tire rubber due to oxidation
4. Nitrogen will leak slower through the tire membrane
(sorry if this is drifting this thread off topic...)
1. Reduction of water vapor, which means a more consistent tire pressure at all temperatures, especially during landing when water wapor will quickly expand, resulting in a sudden and potentially catastrophic increase in tire pressure
2. Nitrogen-only inflation will not add oxygen to a fire should the tire burst
3. Less corrosion of the wheel and breakdown of the tire rubber due to oxidation
4. Nitrogen will leak slower through the tire membrane
(sorry if this is drifting this thread off topic...)
I don't believe that the tire pressure is all that critical. If the placard says 32# I wouldn't go much below that but I do go a little higher (36-38) in a max 44# tire. You can have weather temp swings and still be in range.
Yesterday I went out and had to let a little pressure out of the tires as the ambient temps here are warming. Ontario, Canada
I think it's just as important to have all the tires in the same pressure ballpark, all 36 or all 38 etc. (not 1 tire 30# and one 42# and one 36# and one 44#)
Best wishes to all.
Yesterday I went out and had to let a little pressure out of the tires as the ambient temps here are warming. Ontario, Canada
I think it's just as important to have all the tires in the same pressure ballpark, all 36 or all 38 etc. (not 1 tire 30# and one 42# and one 36# and one 44#)
Best wishes to all.
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1. Reduction of water vapor, which means a more consistent tire pressure at all temperatures, especially during landing when water wapor will quickly expand, resulting in a sudden and potentially catastrophic increase in tire pressure
True, however properly dried air will have the same benefit. When car tires are mounted a water based lubricant is used, usually in great excess. This nullifies any benefit to the dry gas.
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2. Nitrogen-only inflation will not add oxygen to a fire should the tire burst
This is the number one, and only reason for using nitrogen. The FAA mandates the use of an inert gas. It doesn't have to be nitrogen. Nitrogen is cheap and easy to obtain, and fits the requirements. Argon would be better at the secondary "benefit" touted for nitrogen, of lower leakage, but is far more expensive.
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3. Less corrosion of the wheel and breakdown of the tire rubber due to oxidation
True, but again moot. The outside of the tire is exposed to oxygen, UV, ozone, and moisture. Tires rot from the outside regardless of the interior fill.
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4. Nitrogen will leak slower through the tire membrane
True, but again since air is 78% nitrogen, the practical difference does not prove to be any real benefit.
If you can get nitrogen free, use it. If you are being charged for it, you are being ripped off.
Ed
1. Reduction of water vapor, which means a more consistent tire pressure at all temperatures, especially during landing when water wapor will quickly expand, resulting in a sudden and potentially catastrophic increase in tire pressure
True, however properly dried air will have the same benefit. When car tires are mounted a water based lubricant is used, usually in great excess. This nullifies any benefit to the dry gas.
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2. Nitrogen-only inflation will not add oxygen to a fire should the tire burst
This is the number one, and only reason for using nitrogen. The FAA mandates the use of an inert gas. It doesn't have to be nitrogen. Nitrogen is cheap and easy to obtain, and fits the requirements. Argon would be better at the secondary "benefit" touted for nitrogen, of lower leakage, but is far more expensive.
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3. Less corrosion of the wheel and breakdown of the tire rubber due to oxidation
True, but again moot. The outside of the tire is exposed to oxygen, UV, ozone, and moisture. Tires rot from the outside regardless of the interior fill.
Quote:
4. Nitrogen will leak slower through the tire membrane
True, but again since air is 78% nitrogen, the practical difference does not prove to be any real benefit.
If you can get nitrogen free, use it. If you are being charged for it, you are being ripped off.
Ed
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I cannot believe the snake oil salesman are so busy! And believe me, Nitrogen is purest snake oil!
This link was posted before but it's worth it if it saves somebody.
http://www.barrystiretech.com/nitrogeninflation.html
This link was posted before but it's worth it if it saves somebody.
http://www.barrystiretech.com/nitrogeninflation.html
Originally Posted By: edhackett
True, however properly dried air will have the same benefit. When car tires are mounted a water based lubricant is used, usually in great excess. This nullifies any benefit to the dry gas.
Not to mention that cars don't tend to go from 40,000 feet elevation down to sea level in a matter of minutes, either. And corrosion, not likely. Steel wheels on taxi usage lasted forever and a day, and I've never seen a tire rot from the inside out.
Nitrogen might have certain very marginal benefits, but those benefits don't outweigh the financial costs. I'll use nitrogen, no problem, if a shop wishes to trade me their nitrogen machine for my air compressor, straight across.
True, however properly dried air will have the same benefit. When car tires are mounted a water based lubricant is used, usually in great excess. This nullifies any benefit to the dry gas.
Not to mention that cars don't tend to go from 40,000 feet elevation down to sea level in a matter of minutes, either. And corrosion, not likely. Steel wheels on taxi usage lasted forever and a day, and I've never seen a tire rot from the inside out.
Nitrogen might have certain very marginal benefits, but those benefits don't outweigh the financial costs. I'll use nitrogen, no problem, if a shop wishes to trade me their nitrogen machine for my air compressor, straight across.
Originally Posted By: edhackett
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4. Nitrogen will leak slower through the tire membrane
True, but again since air is 78% nitrogen, the practical difference does not prove to be any real benefit.
Huh? Leaking slower is not a "real benefit"? I suspect the phrase "net benefit" would describe what you intended to convey due to your costs vs benefits analysis.
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4. Nitrogen will leak slower through the tire membrane
True, but again since air is 78% nitrogen, the practical difference does not prove to be any real benefit.
Huh? Leaking slower is not a "real benefit"? I suspect the phrase "net benefit" would describe what you intended to convey due to your costs vs benefits analysis.
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Tire pressures are listed for cold measure, using "regular" air; and I'd bet they factored in the temperature/pressure rise once driving.
If pure nitrogen expands less/dissipates more heat; then the factory measurement is off now, somewhat. Splitting hairs, sure, but still.
If pure nitrogen expands less/dissipates more heat; then the factory measurement is off now, somewhat. Splitting hairs, sure, but still.
Originally Posted By: Carbon
Originally Posted By: edhackett
Quote:
4. Nitrogen will leak slower through the tire membrane
True, but again since air is 78% nitrogen, the practical difference does not prove to be any real benefit.
Huh? Leaking slower is not a "real benefit"? I suspect the phrase "net benefit" would describe what you intended to convey due to your costs vs benefits analysis.
What's the "real difference" in rate between air and N2 ?
And if there was a significant difference, there would be a race between the two following scenarios:
1) the partial pressure difference of oxygen would drive oxygen into the tyre, until equilibrium, dangerously overinflating the tyre; or
2) oxygen would leak out at every inflation, resulting in almost complete nitrogen fill.
As it actually exists, the median between 1 and 2 seems to be matched by air on one side,and air at moderate pressure on the other...
Originally Posted By: edhackett
Quote:
4. Nitrogen will leak slower through the tire membrane
True, but again since air is 78% nitrogen, the practical difference does not prove to be any real benefit.
Huh? Leaking slower is not a "real benefit"? I suspect the phrase "net benefit" would describe what you intended to convey due to your costs vs benefits analysis.
What's the "real difference" in rate between air and N2 ?
And if there was a significant difference, there would be a race between the two following scenarios:
1) the partial pressure difference of oxygen would drive oxygen into the tyre, until equilibrium, dangerously overinflating the tyre; or
2) oxygen would leak out at every inflation, resulting in almost complete nitrogen fill.
As it actually exists, the median between 1 and 2 seems to be matched by air on one side,and air at moderate pressure on the other...
I check my tire pressure at least twice a month, or when the temperature outside increases/decreases significantly (about 10 degrees). Sometimes, I check the tires everyday. That way, I don't have to be worried about over inflation or under inflation. Today, the temperature had dropped 15 degrees so I had to add air.
When tires heat up, the pressure raises but there's still the same amount of air in there. That's because air molecules move faster when they heat up.
So only check the tires when they're cold and don't worry about hot tire pressure.
When tires heat up, the pressure raises but there's still the same amount of air in there. That's because air molecules move faster when they heat up.
So only check the tires when they're cold and don't worry about hot tire pressure.
The nitrogen produced by the nitrogen generators used for tire inflation only produce about 95% pure nitrogen. You are looking at the difference of a fill gas with ~14% oxygen. The maximum difference in leakage will be 0.14X the difference between N2 and O2, which is tiny, and will vary from tire to tire.
I looked at one of the green valve stem caps on a friends car. It was a high quality piece with a rubber seal. I suspect that people who claim that nitrogen doesn't leak out of their tires are actually seeing the benefit of a quality valve stem cap vs. the plain plastic, purely cosmetic caps usually found.
Ed
I looked at one of the green valve stem caps on a friends car. It was a high quality piece with a rubber seal. I suspect that people who claim that nitrogen doesn't leak out of their tires are actually seeing the benefit of a quality valve stem cap vs. the plain plastic, purely cosmetic caps usually found.
Ed
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