Also the Nitrogen lobby sometimes claims that with Nitrogen filled the pressure-loss is 4 times as less.
Would mean that if a 35 psi filled tyre looses 3,5 psi in a year, as tested once, the Nitrogen filled tyre looses only 0.9 psi in that year.
In real it tested 2.2 psi loss of Nitrogen in a year.
Means 3.5 psi/ 2.2psi= 1.59 x as fast
And part of that 2.2 psi for N2 is because, as Capri-racer explained, because the 3 psi partial pressure of oxigen in the outside air gives difusion into the tire. So tire with 100% N2 lost a bit more then 2.2 psi of N2 in that year, and was compensated by Oxigen going into the tyre.
Oxigen diffusion rate is 3 to 4 times that of Nitrogen.
But roughly 20% oxigen in air.
Little rough calculation.
Air: (N2) 0.8x 1 + (O2) 0.2 x 4= 1.6
100,000 % Nitrogen: 1x1= 1
So in real 1.6x as fast or as much Air lost then 100% Nitrogen, and not 4
See here the exageration .
If difusion rate Oxigen 3x as fast 1.4 times as fast and not 3x as they claim
And also often claimed 1 psi loss of air per month, and in the test 3.5 psi in a year, so about 1/3th psi per month.
Great, all this talk about nitrogen vs air crap reminded me that I need to let some psi out of my tires, noticed the last ride down the I65 was very rough…
+1
About a week ago, I took a few psi out of my tires, but as of today, they are already 5 psi over the mfr’s recommended pressure after driving ~5 miles in 90+ degree temps.
The vehicle goes to the dealership tomorrow for an oil change and tire rotation, and it should be interesting to see if they reduce the tire pressure in light of the predicted 100+ degree forecast. I’m not going to fiddle with the pressure today, and I’ll just re-check it the following morning when they are “cold”.
Be carefull with yust letting out air, first calculate what pressure realy needed for your weights on axle or axle-end and speed used.
Risk if you let out to much is overheated tires.
Then you have an exelent comfort for mayby a year, but meanwhie the beginning internal cracks , created by mayby only once overheated, tear further, until at a certain moment tyre blows or treath separates. Then other factors are blamed, like high pressure by higher temperatures.
Reaction to post before mine:
At higher ambiënt temperature the tire needs the higher pressure, it automatically gets, to give lesser deflection, so lesser heatproduction at same speed. This because cooling down of tyre-material is also lesser, because of lesser temperature differences between tyre-material and in-and out-side tyre air.
So in short, at 40 degrC/ 104 degrF ambiënt temperature, never lower cold measured ( when in and out tyre same temperature, so at 40 degrC outside, also 40 degrC in tyre) or warm pressure ( by driving ) , then yust creates overheated tyres.
In my experience, a TPMS alert doesn’t happen until the tire is significantly underinflated. If your system is like that, it sounds like you should be checking your tire pressure more often.
Now just who is going to do that ? I guess you want me to set the tires at xx psi if I am just driving around town and something else if I am taking the turnpike to Oklahoma City. What should I do if I pickup some bags of mulch on the way home ?
Well since I adjusted the psi last winter when it was freezing weather, and the place card states 32 psi cold (I had set them to 35 psi for when the temp dropped much lower) and now it is in the 90’s, I just check and they are at 36psi over night cold, and after5-10 minutes on the interstate they were up to 38-39 psi a few days ago, I think I am good with letting a few psi out of them, but thank you for your concern…
Besides, my buttometer said I had too much air in them…
Exactly!
I normally keep my tires inflated to 3 psi over the mfr’s recommended pressure in order to give me a little margin for “error”, and also because I prefer the ride and handling with a few extra psi. But, there is a limit, so when temps begin to climb, I always reduce the cold psi a bit–still maintaining that 3 psi “edge”. Conversely, when temps drop in the late autumn, I add a few psi in order to maintain that slight “edge”.
The tires will always gain several psi from high-speed driving, and from high temps, but I always start with that 3 psi edge and I don’t worry about the higher psi after a long, hot expressway run.
I wasn’t going to convert from weight percent to volume percent. If tires are filled with air, the air has water in it, even if it is stripped and dried. Manufactured air has very little water because it is made from nitrogen and oxygen that was distilled. The water and other usual contaminants are removed in the distilling process at -125C. Oxygen boils at -183C. I’m not going through vacuum graphs that I have. They show how vacuum level changes the boiling and freezing points of gaseous elements and water.
I use my own air from my own compressor which I suppose is 70% nitrogen. I just don’t like those green valve cps. So I’ll just keep doing what has worked for 50 years.
There’s oxygen in the atmosphere only because it’s a waste product of some living things. The first organisms were anaerobes, which means they didn’t use oxygen - but they created it as a waste product. When the oxygen level of the atmosphere got high enough oxygen poisoned the obligatory anaerobes. Years ago ‘The Atlantic’ invited reader submissions for the worst environmental catastrophe. They didn’t choose my nominee, the oxygenation of the atmosphere, though it probably killed more living things than any other. Agriculture comes in second.
When Star Trek landed on a lifeless planet with a breathable atmosphere - you know that’s impossible.
No, it isn’t: oxygen is reactive. Without plants and bacteria continuously creating oxygen there would be none in the Earth’s atmosphere - or any other planet’s. Earth’s had none until the organisms that create it appeared. After they all die, about 300 years later, there’ll be none.
