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Nitrogen in stock tires

Discussion in 'Model S: Driving Dynamics' started by GasKilla, Dec 13, 2015.

  1. GasKilla

    GasKilla No Gas Know Peace

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    Has anyone replaced the "normal" air in their stock tires with nitrogen? Was there a noticeable performance difference?

    I know now places like the Costco tire center put nitrogen in the tires they install, but I doubt the Tesla Factory is using nitrogen. So I'm wondering if any performance difference, increased range, etc. can be achieved by switching to nirogen.
     
  2. eye.surgeon

    eye.surgeon Member

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    The only real world benefit is stability of tire pressure. There are no other performance differences. The pressures don't change with temperature.
     
  3. Cyclone

    Cyclone Active Member

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    I put 78% nitrogen in my stock tires :)
     
  4. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Nitrogen inflation for normal road use is very close to a scam. If the compressor air is dry there is no practical difference. The best you can say about it is that it does no harm if it's free.

    Nitrogen is used by racers for one of two reasons: 1. it's guaranteed to be dry so suspensions can be tuned to get that last 1/100th of a second lap time reduction. 2. At some racetracks there is no electricity in the pits so a regular compressor can't be used.

    Nitrogen is also used to inflate tires in underground mine vehicles, subways, and airplanes. This is so that if there is a fire no oxygen will be added to the mix. Above ground (or below cruising altitude) there is enough oxygen that the amount in a tire won't matter.
     
  5. pmadflyer

    pmadflyer Member

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    This!

    One of the "benefits," is more time between filling up. Assuming oxygen passes through the walls more easily, every time you fill up, the percentage of nitrogen increases. Water content in the air might be a problem, but I doubt know. The pressure increase with temperature is assumed, and desirable in both the engineering design of roads and tires, increases efficiency when cool air pressure is properly maintained. I thought the last one was interesting in class, but it makes sense. Traction increases with softer, warm tires, and the increased pressure decreases rolling friction, a HUGE source of wasted energy.

    I'm with Cyclone though, I also use mostly nitrogen.
     
  6. kort677

    kort677 Active Member

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    the only benefit to nitrogen is that loss of pressure will be minimal when there is a drop in temperature.
     
  7. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Which was true before butyl (oxygen tight) rubber was used in tubes and tubeless liners. That was a long time ago. The Leaf came with nitrogen and I have to adjust the pressures just as often as I do in the Model S, so I am very skeptical about more time between adjustments (which are based on temperature).

    Water vapour expands more rapidly than gas when heated, but it only a concern for racers (unless there is a gross amount of water).

    - - - Updated - - -

    That is not correct. 100% nitrogen or nitrogen plus oxygen (and a few other gases) will expand and contract at the same rate if dry. If not dry, whether you add 2 psi or 2.5 psi doesn't change the frequency of a check or the time involved by any material amount.
     
  8. Johan

    Johan Took a TSLA bear test. Came back negative.

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    pV=nRT (the general gas equation)

    (note that the type of gas or gas mixture does not change the fact that pressure is directly related to temperature in a linear fashion).
     
  9. Branzo90D

    Branzo90D Salt and Pepper

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    Thanks, Johan, for mentioning the ideal gas law. I can tell you that, even with slightly moist air being put into your tires, the difference between "moist air" and dry nitrogen in terms of pressure change vs. temperature would not be more than a couple of percent. They would both increase with increasing temperature and both decrease with decreasing temperature. The difference in cost, however, is quite measurable. Sure, the nitrogen might save you 1 or 2 psi, but is that worth the extra cost? :smile:

    As mentioned by jerry33 this is really a scam, in my opinion. Don't pay for nitrogen inflation. Are you going to return there when the temperature drops to get some more nitrogen? I doubt most people will.

    Check this article: http://www.consumerreports.org/cro/news/2007/10/tires-nitrogen-air-loss-study/index.htm
     
  10. Patrick W

    Patrick W Member

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    First time I read that it went right over my head. (and I teach physics)

    Wasn't until a few posts down that it sunk in.

    Good joke! :)
     
  11. Uncle Paul

    Uncle Paul Member

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    If Nitrogen for passenger tires was free, then everyone would prefer using it due to it's benefits, however if there is a cost for it, most all would go for air if that was free. Differences so slight as to be unnoticible on a typical passenger car.
     
  12. DrComputer

    DrComputer Member

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    Costco uses Nitrogen by default at no extra charge. You can stop by the tire center with your non-Costco tires and they will fill you up for free.
     
  13. ecarfan

    ecarfan Well-Known Member

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    #13 ecarfan, Dec 13, 2015
    Last edited: Dec 14, 2015
  14. Thud

    Thud Member

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    No... the loss of pressure will be more predictable when there is a drop in temperature. Pure nitrogen doesn't change the ideal gas law (pV = nRT), it just adheres more closely to it compared to atmospheric air.


    It's pretty much useless except for racing.
     
  15. sillydriver

    sillydriver Member

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    All it is is a margin enhancer for automotive dealership service departments.
     
  16. brucet999

    brucet999 Active Member

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    Because, unlike oxygen, nitrogen does not behave like a gas? :)
     
  17. sillydriver

    sillydriver Member

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    #17 sillydriver, Dec 15, 2015
    Last edited: Dec 15, 2015
    I'm skeptical of benefits from nitrogen, but I think the (small) difference is not due to the nitrogen itself but the fact that bottled nitrogen contains no water vapor. In very humid air at summer temperatures I think the partial pressure of water vapor is around 4% of atmospheric pressure, while at freezing it's less than 1% because the capacity of air to carry water declines exponentially with temperature (in cold air the water condenses out as fog or dew). Most of the water inside the cooling tire condenses out and no longer adds its partial pressure to the total pressure in the tire. So if pumped up with humid summer air, a tire will lose roughly 1 psi more as the temp falls to freezing than a tire filled with a completely dry gas like bottled nitrogen. A very small effect, but I think that's what the nitrogen proponents are talking about.
     
  18. zzzzdoc

    zzzzdoc Member

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    I'll just steal a few quotes from the above link to demonstrate the kookiness of this:

    "O2 permeates faster through rubber than does N2...

    Since that is correct, your tires would approach 100% Nitrogen over time.
    If you start with 79% Nitrogen and 21% Oxygen, and you are losing Oxygen preferentially, your Nitrogen concentration increases. Even after adding with 79% N2 and 21% O2, your N2 concentration is higher than air.

    With each fill you will have a higher and higher nitrogen content. Just one more reason to be suspicious of all the "benefits" promised by Nitrogen fill proponents. :)


    If you do the math, and assume that only the oxygen seeps out of the tire, and the nitrogen remains (not totally accurate, but let's go with that assumption for now, and ignore water vapor):

    Initial tire fill-up: 79% N2, 21% O2
    1st top up: 96% N2, 4% O2
    2nd top up: 99% N2, 1% O2
    3rd top up: ... 99.9% N2, 0.1% O2

    So in a few months after owning the car, you have essentially 100% nitrogen in the tires, for no cost.
     
  19. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    That was correct before oxygen tight rubber (butyl) was used. Now it would only be correct if the tubeless liner was damaged or the tire was not seated properly. Unfortunately, things that were correct years ago are still being touted as correct.
     
  20. GasKilla

    GasKilla No Gas Know Peace

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    So I shouldn't put in free nitrogen from Costco in my tires?
     

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