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Tire Gas

Discussion in 'Model S' started by W0QR, Jul 9, 2015.

  1. W0QR

    W0QR Member

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    #1 W0QR, Jul 9, 2015
    Last edited: Jul 9, 2015
    I decided to just start a new post on this subject. Nitrogen for tires? Px? Tire Px gauge..dial, stick, digital?

    Well, I didn't search for Nitrogen..which is what I should have done and there is a thread. But also discussions about 50 psi for tires as opposed to 45. And I still want to know you ya'll monitor that value.
     
  2. Johan

    Johan Took a TSLA bear test. Came back negative.

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    What model do you have? Recommend pressures differ. Lots of threads on gauges and pressures. I run 50 psi on Goodyear 19" (P85 classic). Most of us run with a mixture of 78% nitrogen, 21% oxygen, some Neon, Argon, Xenon, Helium and a dash of CO2 and pollutants (often known to the common man as "air").
     
  3. Larry93428

    Larry93428 Member

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    Good, Johan, so well put. Same mix here.
    ~Larry
     
  4. vdiv

    vdiv Chief Grump

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    Well, it's not the other gasses that are of much concern, it is the water vapor that condenses as it is pumped into the tire and corrodes the wheel and the TPMS sensor. Living in a wet subtropical climate (soon to be tropical) this is a real issue for us as the relative humidity of the "air" has not dropped below 70% since the month of May and unlike the poor California it rains cats and dogs here all the time.

    Using dry compressed nitrogen prevents water from getting inside the tire.
     
  5. CHG-ON

    CHG-ON Still in love after all these miles

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    Excellent point. I have wondered about the value of nitrogen. I assumed that it was just that little bit heavier to reduce slow leaking or parasitic loss, for lack of a better description. But living in drought stricken CA, moisture is not an issue these days. I do find that my 21's lose a slight amount of pressure over a month's time and I need to add perhaps .5-1lbs. But that's about it. On my earlier SUV, I didn't ever have to add air, except when swapping and setting new tires. Ever. Which I found odd, but awfully convenient!

     
  6. jerry33

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

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    1. A line dryer keeps the water out of regular air.

    2. Nitrogen is about 90% a scam (similar to Slick 50). The best thing you can say about it is that it does no harm.

    3. Nitrogen does have some legitimate uses in tires:

    Racers use it because there is often no electricity at the smaller tracks and nitrogen is about as cheap and safe as anything. High end racers use it because it's guaranteed to be dry and so it helps them tune the suspension to get that last 1/100th of a second.

    The other use for nitrogen inflation is underground vehicles (subways and mine vehicles) and airplanes. Nitrogen won't add any oxygen to the mix if a fire should break out. Above ground there is plenty of oxygen so no benefit there.

    4. Since the 1960s air tight rubber (butyl) has been used for tubes and tubeless liners, so nitrogen doesn't help there either.

    As far as water corroding the TPMS sensors, there's water from the mounting fluid, so it won't help all that much.
     
  7. scottreds2k

    scottreds2k Member

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    Not sure I understand the reference to electricity and using nitrogen. If you can bring a tank of nitrogen to a track, you can bring a tank of air.
    I've used nitrogen in tires for autocross to minimize the amount of pressure increase when the tire heats up using air. The amount of pressure increase and adjustment needed between runs is significantly less using nitrogen.
     
  8. jerry33

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

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    If there is no electricity, you can't have a decent size compressor. And yes, nitrogen is guaranteed to be 100% dry.
     
  9. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    PV=nRT. Ideal gas law applies to both nitrogen and oxygen.
    Barry's Tire Tech
     
  10. Thud

    Thud Member

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    Well technically the ideal gas law doesn't apply to either nitrogen or oxygen, since neither one is an ideal gas.
    But it's much more applicable to pure nitrogen than to atmospheric air.
    Nobody is inflating their tires with pure oxygen anyway.
     
  11. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Are you suggesting that for a given increase in temperature the pressure increases more with air than with nitrogen? If so why? Because of water vapor in the air that doesn't behave according to pV=nRT?
     
  12. jerry33

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

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    Correct. If it's not dry the water vapour will expand more than the gas. If dry there is no difference.

    However, the practical difference for normal on-road use is so slight that it's not worth the bother, and if it costs extra it's falls into scam territory. (tire siping and tire truing are other scam practices that show up every few years).
     
  13. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    That's why I posted the link to the study that showed pressure vs. temperature that showed virtually zero difference between the two, validating Jerry's point that it's only needed for that last 0.01 second for special applications.
     
  14. W0QR

    W0QR Member

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    #14 W0QR, Jul 14, 2015
    Last edited: Jul 14, 2015
    Ah, I get it now. Like those rip off MONSTER 'digital' cables at Best Buy.

    But no one commented on their pressure gauges..
     
  15. jerry33

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

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    I've commented several times on pressure gauges, and I'm sure everyone is tired of hearing from me. Pressure gauges are not something you should skimp on. A good one will last a lifetime.
     

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