20IndyRam
Member
- Joined
- Feb 23, 2020
- Posts
- 51
- Reaction score
- 61
- Location
- Extreme Northern Indiana (Michiana)
- Ram Year
- 2020
- Engine
- EcoDiesel
For Dry Air and nitrogen, the Ideal gas law generally applies - Wiki Ideal Gas Law
PV-nrT (temperature is in degrees Kelvin).
For a "dry" gas in a constant volume pressure will increase by 15.1% over a temperature range of 70 to 150F (294.26 to 338.706 degrees K). An equivalent pressure increase would be from 35 to 40.3 PSI.
Your tires are not fixed volume - they will expand with increasing pressure - i.e. the pressure increase will be lower.
Your tires are also permeable. The Nitrogen atom is larger that the Oxygen atom despite nitrogen having a lower atomic weight. Oxygen will permeate through your rubber tires faster than Nitrogen.
Why use nitrogen in tires? For most people there is no good reason. For people that heat their tires above 220F, there is moisture to consider. Most of us will never heat a tire anywhere near 220F (without catastrophic failure). If you do, moisture in an air filled tire will undergo a State change (steam) with a drastic increase in pressure. At this point the ideal gas law no longer applies. Nascar, Formula 1, Indy routinely run in this temperature range. Nitrogen is cheap insurance to make sure there isn't water in the mixture and they can maintain their tire pressures.
Why not use Helium? Helium is the smallest atom. We used it for leak testing welded assemblies and gas tight seals. Over time, it will permeate through Glass and quartz (found out the hard way). A tire would look like a screen door. Did I mention it's not cheap?
Do I use Nitrogen - Sure. Whenever they supply it for free (Belle Tire).
PV-nrT (temperature is in degrees Kelvin).
For a "dry" gas in a constant volume pressure will increase by 15.1% over a temperature range of 70 to 150F (294.26 to 338.706 degrees K). An equivalent pressure increase would be from 35 to 40.3 PSI.
Your tires are not fixed volume - they will expand with increasing pressure - i.e. the pressure increase will be lower.
Your tires are also permeable. The Nitrogen atom is larger that the Oxygen atom despite nitrogen having a lower atomic weight. Oxygen will permeate through your rubber tires faster than Nitrogen.
Why use nitrogen in tires? For most people there is no good reason. For people that heat their tires above 220F, there is moisture to consider. Most of us will never heat a tire anywhere near 220F (without catastrophic failure). If you do, moisture in an air filled tire will undergo a State change (steam) with a drastic increase in pressure. At this point the ideal gas law no longer applies. Nascar, Formula 1, Indy routinely run in this temperature range. Nitrogen is cheap insurance to make sure there isn't water in the mixture and they can maintain their tire pressures.
Why not use Helium? Helium is the smallest atom. We used it for leak testing welded assemblies and gas tight seals. Over time, it will permeate through Glass and quartz (found out the hard way). A tire would look like a screen door. Did I mention it's not cheap?
Do I use Nitrogen - Sure. Whenever they supply it for free (Belle Tire).
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