Saturday, June 3, 2023

# Is inflating tires with nitrogen a good idea?

I saw the following question about inflating tires with nitrogen on an RV forum:

Has anyone researched the cost, etc., of replacing the air in our tires with nitrogen? It’s more stable and does not change pressure with temps. I hate checking my pressures every trip.

Obviously, this person does not read RVtravel.com info on maintenance.

Sorry, but as far as I know all gases follow the “Gas Law”: PV=NRT aka Boyleâ€™s Law (which states that when the temperature of a given mass of confined gas is constant, the product of its pressure and volume is also constant). It is named for Robert Boyle, regarded as the first modern chemist.

P is pressure atmosphere

V is volume in liters (but since the tire’s change in volume is very small, we can assume this is a constant value)

N is how much “stuff” or gas is in the tire aka number of gram-moles of a gas. (A gram-mole, often called gram-molecular weight, is a mass of a substance in grams numerically equal to its molecular weight.) Since we are not adding air or nitrogen (N2), we can consider this to be a constant

R is the ideal gas constant that converts units. This is 0.0821 atmÂ·L/molÂ·K

T is temperature in degrees, Kelvin

Air is 78% N2, so I see no advantage of changing the “gas” inside a tire unless you are racing INDY, F1, or NASCAR.

You should be running a TPMS on your RV, as just checking the pressure in the morning will not give you any warning of a loss of pressure due to a small leak or puncture as soon as you pull out of the campground.

Even if a company offered “free” N2 inflation, it still costs you money and time to travel to their location. So, clearly, a negligible benefit does not offset the real costs.

I covered this topic in detail sufficient to make your eyes glaze over in my RV Tire Safety blog. If you want the Engineering answer, you can read it HERE.

I would really just suggest you use a TPMS (tire pressure monitoring system). Remember that the TPMS pressure readings will be slightly different (+/- 2 psi or so) between each tire. Do not get focused on the absolute pressure reading, and remember you are concerned when one tire loses more pressure than the other tires.

Note: Even when I was racing my car at Daytona, Watkins Glen, Riverside, or Mid-Ohio,Â  I did not use nitrogen because of a theoretically smaller change in tire pressure.

Have a tire question? Ask Roger on his RV Tires Forum here. It’s hosted by RVtravel.com and moderated by Roger. He’ll be happy to help you.

Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.

Â ##RVT1099

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Phil
1 month ago

The main reason that race teams use N2 is it is dry as in no water vapor. Water vapor when heated changes the pressure increases and based on the humidity causes inconsistent pressure increases which the teams canâ€™t control. As nascar teams sometimes are changing pressures to as little as Â¼ psi the water vapor becomes something that can become a variable that canâ€™t be factored in calculations for what the pressure increase will be and result in inconsistent handling of the race car. This is not a factor in street cars as nobody needs that precise of tire pressures in street cars. Normal air with zero humidity would give the same results of dry nitrogen but is not normally available as a commercial product.

Tom M
1 month ago

Thanks Roger for your always valuable information.

Leonard
1 month ago

I couldn’t agree more on having a TPMS. We have ten sensors for our 5th wheel and dually truck. One of the best accessories that I have ever bought!

Jewel
1 month ago

I like the forums and Facebook groups for random common interests and discussions but get so tired of seeing new, inexperienced RVers use these groups to ask questions as if these were experts. Not all advice is the the same and you have to qualify every suggestion before you take it as fact …not that there arent good answers but how do these get weeded out when the asker just takes the answer he likes best?

anyway, good response to the nitrogen “debate”

(I do hope you were joking about Kelvin…which is actually the universal unit of temperature, vs Celsius and Fahrenheit)

Roger Marble
1 month ago

If you read the detailed engineering analysis in my blog you will see that the formula does not use Celsius or Fahrenheit but degrees Kelvin. But the good news is that since we are looking at the ratio of Temperature change to learn the ratio of Pressure change, we do not need to do the detailed math conversion.

Dan
1 month ago

Used to own a motorcycle shop where we did tons of tires. People got on the NASCAR uses nitrogen kick and started asking if we could put it their tires. I checked into getting a nitrogen generator to do that. The cheapest one I could find was over \$3000.00. And that was almost 20 years ago. That’s why dealers have to charge for it. Some people would have their tires refilled with it and rave about how smooth the ride was. Yeah. Sure. If you say so.

tom
1 month ago

Local car dealer charges for Nitrogen Fill. A tax on being not bright.

G13
1 month ago

Totally agree with the writer, speaking from experience.