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Thread: Tire air Pressure

  1. #46
    If this has already been discussed then just ignore my post. I use nitrogen in my tires and it goes a long way towards eliminating the pressure from changing with temperature changes. I maintain a fairly constant 34 lbs. on all four tires and it is monitored and displayed on the dash with a push of a button. Big O tires will check and top off my tires at no charge and I do this prior to any long trip.
    Best Regards,

    Gordon

  2. #47
    Quote Originally Posted by Tom Stenzel View Post
    I remember some of the GM systems used the ABS rotation sensors to monitor the tire pressure. If one tire spun at a different RPM while driving it was assumed one of the tires was mis-inflated. GM pushed to have that accepted as it used no additional sensors, required only a minor software update to the existing computer, and program one more message in the display system. I think it ended up the highway dept disallowed it as four mis-inflated tires would read as just fine.

    When we went shopping for a used car for my daughter there were many cars with the tire monitor system in fault. A sensor would break or a wheel would be changed and the owners just ignored the light. Depending on the price of repair I might be inclined to ignore it too.

    -Tom
    Not only that, but if you replaced one tire with a slightly different size, it would rotate at a different RPM constantly. I had that problem on a car I owned. I had a tire failure on a trip and had to replace it at the nearest tire shop. After that, my cruise control wouldn't work. Eventually found out it was because the two tires on the back were rotating at slightly different RPMs. Had to replace the "new" tire.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  3. #48
    Quote Originally Posted by Gordon Eyre View Post
    If this has already been discussed then just ignore my post. I use nitrogen in my tires and it goes a long way towards eliminating the pressure from changing with temperature changes. I maintain a fairly constant 34 lbs. on all four tires and it is monitored and displayed on the dash with a push of a button. Big O tires will check and top off my tires at no charge and I do this prior to any long trip.
    I've heard that before but I don't understand it. Nitrogen expands and contracts with temperature just like air. After all, regular air is almost 80% nitrogen. If there's some truth to this belief it may be because the nitrogen they put in your tires is "dry" while normal air has some level of humidity.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  4. #49
    Its not do to expansion and contraction. Air leaks thru the rubber sidewalls on tires and nitrogen leaks a lot slower.

    Quote Originally Posted by Mike Henderson View Post
    I've heard that before but I don't understand it. Nitrogen expands and contracts with temperature just like air. After all, regular air is almost 80% nitrogen. If there's some truth to this belief it may be because the nitrogen they put in your tires is "dry" while normal air has some level of humidity.

    Mike
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  5. #50
    Quote Originally Posted by Bert Kemp View Post
    Its not due to expansion and contraction. Air leaks thru the rubber sidewalls on tires and nitrogen leaks a lot slower.
    According to this article, the difference in leaks through the sidewalls is extremely small. And since air is 80% nitrogen, that's kind of what I'd expect. The only way we'd see a difference is if the oxygen in the air leaked at a rapid rate. Nitrogen and oxygen are next to each other in the periodic table with Oxygen being slightly heavier than nitrogen so we'd expect that oxygen would migrate at a slower rate than nitrogen.

    But, in any case, it appears that for ordinary passenger car use, there's not much difference.

    Mike
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  6. #51
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    Quote Originally Posted by Curt Harms View Post
    I have one gauge on a regulator that is filled with some sort of clear oil so the mechanism shouldn't get sticky with age.
    Probably Glycerin. It's there for use in applications where there is vibration. Very common in industry.
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  7. #52
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    Quote Originally Posted by Mike Henderson View Post
    I've heard that before but I don't understand it. Nitrogen expands and contracts with temperature just like air. After all, regular air is almost 80% nitrogen. If there's some truth to this belief it may be because the nitrogen they put in your tires is "dry" while normal air has some level of humidity.

    Mike
    Nitrogen pressure does increase and decrease with temperature, I know that first hand. Certain aircraft use high pressure nitrogen in emergency systems as well as in tires. A system serviced to 2000 p.s.i. in a warm climate may read 1700 p.s.i. after sitting in a cold climate for several hours. Go back to the warm climate, let it sit several hours and the pressure is back up to 2000 p.s.i. with no servicing. There's even a temperature/pressure table next to the gauge.

  8. #53
    Nitrogen in car tires is pure marketing hooey. The ideal gas law makes N2 tire pressure stability impossible. Please note the use of the term 'law', it is not called the 'ideal gas suggestion'.

    Putting N2 in your tires allows 2 things: 1. the dealer can charge you $150-$300 over the MSRP (remember dealer's $500 "clear coat protectant" - aka "wax"); and, 2. You can't refill your tires at the local gas station or your shop compressor. So, you have to return to the dealer service bay where they can up-sell you all over again.

    Call me a cynic. Or a realist. ...Or even maybe an engineer?

  9. #54
    I guess it depends on were you get info from.
    From Popular Mechanic's
    From the top: Air is 78 percent nitrogen, just under 21 percent oxygen, and the rest is water vapor, CO2 and small concentrations of noble gases such as neon and argon. We can ignore the other gases.There are several compelling reasons to use pure nitrogen in tires.
    First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that your tire pressures will remain more stable over the long term. Racers figured out pretty quickly that tires filled with nitrogen rather than air also exhibit less pressure change with temperature swings. That means more consistent inflation pressures during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important.
    Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.
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  10. #55
    Quote Originally Posted by Bert Kemp View Post
    I guess it depends on were you get info from.
    From Popular Mechanic's
    From the top: Air is 78 percent nitrogen, just under 21 percent oxygen, and the rest is water vapor, CO2 and small concentrations of noble gases such as neon and argon. We can ignore the other gases.There are several compelling reasons to use pure nitrogen in tires.
    First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that your tire pressures will remain more stable over the long term. Racers figured out pretty quickly that tires filled with nitrogen rather than air also exhibit less pressure change with temperature swings. That means more consistent inflation pressures during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important.
    Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.
    From the same article:
    ++++++++++++++++++++++
    Consumer Reports conducted a study comparing nitrogen versus air loss in tires to determine if this benefit of nitrogen was worth the extra cost. They used 31 pairs of various tire models, filled one tire of each pair to 30 psi with air and the other to the same pressure with nitrogen, then left them outside for a year. At the end of the year, they found that all tires lost pressure. The average pressure loss with air was 3.5 psi; with nitrogen the average loss was 2.2 psi – a difference of only 1.3 psi over a year.
    ++++++++++++++++

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  11. #56
    Quote Originally Posted by Bert Kemp View Post
    I guess it depends on were you get info from.
    From Popular Mechanic's
    From the top: Air is 78 percent nitrogen, just under 21 percent oxygen, and the rest is water vapor, CO2 and small concentrations of noble gases such as neon and argon. We can ignore the other gases.There are several compelling reasons to use pure nitrogen in tires.
    First is that nitrogen is less likely to migrate through tire rubber than is oxygen, which means that your tire pressures will remain more stable over the long term. Racers figured out pretty quickly that tires filled with nitrogen rather than air also exhibit less pressure change with temperature swings. That means more consistent inflation pressures during a race as the tires heat up. And when you're tweaking a race car's handling with half-psi changes, that's important.
    Passenger cars can also benefit from the more stable pressures. But there's more: Humidity (water) is a Bad Thing to have inside a tire. Water, present as a vapor or even as a liquid in a tire, causes more of a pressure change with temperature swings than dry air does. It also promotes corrosion of the steel or aluminum rim.
    I try to get my information about the physical world from researchers in the physical sciences, not from the entertainment media. Please spend your money as you feel appropriate.

  12. #57
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    Quote Originally Posted by Malcolm McLeod View Post
    I try to get my information about the physical world from researchers in the physical sciences, not from the entertainment media. Please spend your money as you feel appropriate.

    I would think (not a chemist) gas mixtures containing oxygen are more chemically reactive than pure nitrogen. Is it enough to matter? I don't know.

  13. #58
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    Quote Originally Posted by Curt Harms View Post
    I would think (not a chemist) gas mixtures containing oxygen are more chemically reactive than pure nitrogen. Is it enough to matter? I don't know.
    The thing to remember is that your tire is not existing in some isolated world... it is surrounded by the nitrogen/oxygen mixture. If you stop to think about it, most tires do not wear out from the inside. And, if the 21% oxygen mixture were that corrosive to tire rubber, you would still have the problem on the outside of the tire, which is the part that is touching the road, and far more important to operating your vehicle safely.

    The thing about the oxygen leakage thing I have never been able to figure out... if over some period of time, the oxygen leaks out of my tires faster than the nitrogen, and I keep refilling them with a mixture that has nearly 5 times as much nitrogen as oxygen, wouldn't my tires eventually become nearly completely filled with nitrogen?

    I used that last one on a car salesman one time, and he responded with "Well, I'm not a chemistry teacher, so..." I let him know that I was a chemistry (and physics) teacher, and that caused the conversation to move along to non-chemical ways he could remove money from my pocket and put it into his .

  14. #59
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    Quote Originally Posted by John M Wilson View Post
    The thing to remember is that your tire is not existing in some isolated world... it is surrounded by the nitrogen/oxygen mixture. If you stop to think about it, most tires do not wear out from the inside. And, if the 21% oxygen mixture were that corrosive to tire rubber, you would still have the problem on the outside of the tire, which is the part that is touching the road, and far more important to operating your vehicle safely.

    The thing about the oxygen leakage thing I have never been able to figure out... if over some period of time, the oxygen leaks out of my tires faster than the nitrogen, and I keep refilling them with a mixture that has nearly 5 times as much nitrogen as oxygen, wouldn't my tires eventually become nearly completely filled with nitrogen?

    I used that last one on a car salesman one time, and he responded with "Well, I'm not a chemistry teacher, so..." I let him know that I was a chemistry (and physics) teacher, and that caused the conversation to move along to non-chemical ways he could remove money from my pocket and put it into his .
    Ah, that got ya moment. Priceless.
    NOW you tell me...

  15. #60
    At one time, I thought it might be the moisture content in air - while the nitrogen was dry. But think about the compressor in your shop: When you compress air, it can't hold as much moisture as when it's at a lower pressure. That's why you get water in your tank. And the air compressors in a service station probably compress to at least 150 lbs/sq" so the air coming out of the hose is dryer than the ambient air. It isn't completely dry, but it would be very low humidity. So I'd think that moisture in the air in the tire would be a small factor.

    Overall, I can't see any significant advantage to all nitrogen in your tires - but I'm willing to listen.

    Mike

    [I suspect the "nitrogen" that the tire shops put in your tires is not "pure". Getting every last contaminant out of something is extremely difficult and I suspect they buy "cheap" (non-pure) nitrogen, probably because it doesn't matter.]
    Last edited by Mike Henderson; 12-03-2016 at 1:13 PM.
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