Nitrogen pressure fluctuation due to tempurature?

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I bought for new tires and had them filled with nitrogen. Had them for about a month. The tempurature has been all over the map in NYC. The other day it was 85, and now it's 45. I wanna say it was 60 degrees when the tires were filled.

I thought nitrogen (because of the lack of moisture, and yes I know about the ideal gas law) was less susceptible to pressure change due to temperature. I went to my car after work and caught a pressure warning light. Do you think that a temp change like we had lately would throw a light? Or do I have a leak?
 
I suspect a leak unless they were filled very close to the trigger point for your LTP Warning.

My truck came with nitrogen fill from the factory and I would say the psi change with temperature is about 1 degree for every 10 degrees. It should also permeate through the sidewalls at only 1/3 the rate of air. You shouldnt be down but about 2 lb everything considered.
 
Originally Posted By: hardcore302
I thought nitrogen (because of the lack of moisture, and yes I know about the ideal gas law) was less susceptible to pressure change due to temperature.


How can you claim to know about the universal gas law and then say this???

Sigh...
 
Originally Posted By: Gene K
I suspect a leak unless they were filled very close to the trigger point for your LTP Warning.

My truck came with nitrogen fill from the factory and I would say the psi change with temperature is about 1 degree for every 10 degrees. It should also permeate through the sidewalls at only 1/3 the rate of air. You shouldnt be down but about 2 lb everything considered.


No...Nitrogen permeates through the rubber at 1/3 the rate of Oxygen...but air is 78% Nitrogen, so the difference is very small...

Who says that 302's tires were filled to exactly the right pressure to begin with? What was the shop temp when they were filled? How long ago was it?

I've made this point several times: You have to check your tires just as often with N2...but hey, at least the tire shop is getting paid more...
 
This happened all the time on my 08 Kia Optima......one day it would be 60 degrees......next day (after work) it would be 90 degrees.....and yea....about every month and a half, I was checking/topping off PSI :p


Dealer said the light would come on if the PSI in 1 tire was different from the "other 3).....all were checked for leaks, no leaks found.....just a change in ambient temps lol.
 
Originally Posted By: Astro14
Originally Posted By: Gene K
I suspect a leak unless they were filled very close to the trigger point for your LTP Warning.

My truck came with nitrogen fill from the factory and I would say the psi change with temperature is about 1 degree for every 10 degrees. It should also permeate through the sidewalls at only 1/3 the rate of air. You shouldnt be down but about 2 lb everything considered.


No...Nitrogen permeates through the rubber at 1/3 the rate of Oxygen...but air is 78% Nitrogen, so the difference is very small...

Who says that 302's tires were filled to exactly the right pressure to begin with? What was the shop temp when they were filled? How long ago was it?

I've made this point several times: You have to check your tires just as often with N2...but hey, at least the tire shop is getting paid more...


True. Brainfade. At any rate it shouldnt be over 3 psi with a 15 degree temp drop and 1 months time. I believe the S197 Mustang LTP Warning goes off at 26 psi if I remember correctly.
 
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As others have said, aside from leaks, it all depends how close the tire was filled to the triggering point. My G's tires were set to 33 psi in my 10 C garage. When it spent a couple hours outside at -20 C this winter, the warning light came on.
 
Originally Posted By: ahoier
Dealer said the light would come on if the PSI in 1 tire was different from the "other 3)


That was true of the indirect systems that tried to use ABS sensors, but your car has a sensor in each wheel. You could have all four tires deflate at the same rate, and you'd still get a warning light.
 
Originally Posted By: hardcore302
I thought nitrogen (because of the lack of moisture, and yes I know about the ideal gas law) was less susceptible to pressure change due to temperature.



http://www.barrystiretech.com/nitrogeninflation.html

Quote:
A rule of thumb is that for every 10°F, the tire's pressure will change 1 psi.

That means that from the summer's high of 90°F to winter's 0°F, the pressure in your tire will drop 9 psi - DANGEROUSLY underinflated!

This will happen no matter what gas is used as an inflation medium.
 
Also, how has the shop extracted the existing air and moisture that was already in the tire before they started pumping in the nitrogen?
 
Originally Posted By: hardcore302
Well, turns out I got a nail in it.


There you go. I guess the simplest explanation tends to be the best one. It looks like you keep an eye on your tire pressure regularly. Therefore, if pressure goes down significantly between regular checks, you have a leak.
wink.gif


I did have a leak in the G, too, a couple months back. The TPMS was picky enough to catch it long before riding on a low tire was even an issue. After it went off, I monitored it closely. I was losing 1 PSI per day, when the other tires weren't. Therefore, a leak.
 
Originally Posted By: Quattro Pete
Also, how has the shop extracted the existing air and moisture that was already in the tire before they started pumping in the nitrogen?
I asked the local Costco tire manager that soon after they started using their nitrogen concentrator. His response was that they use about as much from the tank flushing as filling.

Re the question on it being dry ... it is my understanding of the concentration process that the water vapor is removed by the same membrane process that removes the oxygen. BUT I DON'T KNOW.
 
I'd also ask Kestas' question...

there's more water in the assembly lubricant than could possibly be carried in with the air.
 
Nitrogen does fluctuate with temp I dont care what application. I work on a nitrogen boosted hydraulic powered gun mount and when we take readings there is a plate with a 20 psi difference for every 10 deg rise in ambient temp.
 
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