u will get the tpms light durring the winter do to the temp of the air the tire pressure will drop. and if it drops bellow 28 psi the light will go on in the jk

 

Sorry, you are wrong or miss informed. N2 at a purity rate of 94% or higher is a stable gas. Stable gasses do not expand or contract with temperature change. This is one of the main reason airlines use N2 in their tires. The temp is 20 or more degrees cooler at 30,000 feet, if they did not use N2 they would risk blowouts on landing. The atmosphere is 79% N2, but the other 21% is what makes it unstable. I have been selling compressed gasses for over 20 years and have a little bit of knowledge on why different gasses are used for different things.

Ever wonder why a good refrigeration company will use nitrogen in all new refrigeration installs for leak testing, it's because the pressure does not change with temp. Put 100 lbs. of air in the line and at the end of the day it will be down to 95 or 90. Now is that a leak or the air contracting from cooling? They use N2 and don't have to question how much of the pressure drop is from the temp. They know if it drops it's a leak.

 

Incorrect. All gases expand and contract with temperature change, it is a fundamental property of physics. All gases also change temperature with changes in pressure. That being said, the only difference between compressed air and compressed nitrogen is the other 21%, and of that, only water vapor makes much difference. Yes, nitrogen is an oxidizing agent like O2 is, but that doesn't make a huge difference in tires because they aren't readily oxidized, like metal is.

 

I should have been more clear. Yes it is effected by temperature but a stable gas such as high purity nitrogen will have much less varience than an unstable gas such as compressed air wich has impurities. The impurities are what cause drastic changes. The water molecules expand and contract easily with temperature change.

Put a n2 filled tire and a compressed air filled tire side by side, you will see larger variences in the air filled tire as the outside temp changes.

 

Just a side note,, my jk does trigger on the spare,, and it didnt take more than 200 yards to reset at 10mph.. One ding for the spare.. 4 for all 4 tires,, Had to refill for the low temp,, went right up to 35 as it was just going to get colder and it wouldnt reset.. but changed to one ding,, Checked the spare and filled it,, light went off one lap around the parkinglot at work..

 

Pressure X Volume / temp = Pressure X Volume/ temp




ideal gas law says if say tire hold 40 liters of air at 35 psi, at 80, and the temp changes to 30 and volume of tire hasnt changed, you should be able to predict the new temp by using this equation...it works with any gas nitrogen or air or any other gas...

basically every cold day we have people rolling into our shop with tpms lights...

 

If the jeep is smart enough to tell you when your tire/tires are low then it should be smart enough to compensate for the temp. drop, it knows what temp. it is. JMO

 

That's funny, but your tires are still low and need to be filled regardless. Unless you've got a special mod you'd like to share.

 

but thats methane,, and expands/contracts at a greater % than normal air.. also is very flamable,, so dont drive near any open flames...

 

My chime sounded a week ago when the temperature dropped into the low 20s. I checked all four road wheels and pressure was at 35 psi (I pumped them up to 37 about a week prior in anticipation of the cold). The spare was down to 26 psi. I added pressure, up to 36 psi. Chime ceased....

The Manual is simply incorrect.


My regards,

Widewing