Cold Weather TPMS
JK Newbie
Joined: Aug 2007
Posts: 27
Likes: 0
From: new jersey
temp vs pressure
in theory only , the body computer monitors tire pressure even when car isnt running, much the way it car does an evap test with natural vacuum when the car is off....
so you get up in the morning and your tire light is on and drive on down to the gas station (heat of friction warms tires thus raising pressure) you then fill the tires with air from a compressor which more than likey inside a building which even in my shop is 50 degrees in the winter....meaning the air you put in the tires is 50 degrees too....then you park the car at night and the temps drop to 10 or lower and the body module says "ding" so when you next start the car light is on...
dont forget depending which generation tpms system you have it also measures diferential of pressures between the tires....3 lb high on one and 3 lb low on another will also flag the light......
havent seen the problem yet on jeep/dodge/chryslers but some imports if you rotate the tires, the the car needs to be reprogrammed so that it knows where and which tires are front and back.....does the new jeep system identify the specific wheel ?
ps funny story....where i live a lot of people come in which trucks that have the spare under the car and say the tire light is on only to find that the restaurant valet or parking attendnt stole the spare for the value of the rim...had 5 customer come in w lexus suv last month, same problem...hee hee hee
so you get up in the morning and your tire light is on and drive on down to the gas station (heat of friction warms tires thus raising pressure) you then fill the tires with air from a compressor which more than likey inside a building which even in my shop is 50 degrees in the winter....meaning the air you put in the tires is 50 degrees too....then you park the car at night and the temps drop to 10 or lower and the body module says "ding" so when you next start the car light is on...
dont forget depending which generation tpms system you have it also measures diferential of pressures between the tires....3 lb high on one and 3 lb low on another will also flag the light......
havent seen the problem yet on jeep/dodge/chryslers but some imports if you rotate the tires, the the car needs to be reprogrammed so that it knows where and which tires are front and back.....does the new jeep system identify the specific wheel ?
ps funny story....where i live a lot of people come in which trucks that have the spare under the car and say the tire light is on only to find that the restaurant valet or parking attendnt stole the spare for the value of the rim...had 5 customer come in w lexus suv last month, same problem...hee hee hee
JK Enthusiast
Joined: Apr 2008
Posts: 163
Likes: 0
From: Marysville, Ca
Mine dinged once and there was the (!) symbol. checked my tire pressure they where all at 30 psi except 1 was at 28psi. the spare was left at 30 psi only because the air hose would not reach without me turning around. (The (!) went away.) I did not have time to turn around because, I was running late to get my oil changed and my tires rotated.
I guess the computer is pretty smart.
Last edited by macanto66; Dec 7, 2008 at 06:46 PM.
JK Enthusiast
Joined: Dec 2007
Posts: 361
Likes: 0
From: Marysville, Ohio
Mine dinged about three weeks ago. I check every tire even the spare and the range was between 30-32 psi. I took each one up to 35psi and everything is back to normal. One thing I did notice was... I didn't check the tires for about a week and the "ding" went from one ding when I started the Jeep to four dings when I started up! So I assumed all four tires needed air. Kind of cool.
JK Junkie
Joined: Aug 2007
Posts: 2,944
Likes: 0
From: Gilbert, AZ
Don't you love an expert.
Some of the main benefits of using N2 as an inflation medium are: higher air pressure retention due to lower permeability than O2 through IIR, NR, and SBR compounds (which leads to improved gas mileage); linear volume expansion with temperature because of nitrogen's inherently low water absorption characteristics; and the expected improvement in structural durability due to
a significant reduction in rubber oxidation (oxidation caused by air from the cavity being forced into the tire carcass)
The characteristic linear volume expansion with temperature because of nitrogen's inherently low water absorption characteristics is no benefit to the average driver because the handling requirements for daily commuting are nowhere near as demanding as for racing; the improvement would be negligible and imperceptible.
AKA Nitrogen will not be absorbed by or commute through the rubber of your tires as fast as air (useful if your storing your vehicle for years), and it won't auto-ignite (not an issue unless your running at high speeds or with huge tires)
You give some good points, but Jeep tires don't often find themselves at 30,000 ft one moment and 0ft the next (where water vapor may condense and cause a 'big' issue) nor are they being used to calibrate temperature dependent systems (refrigeration) where a true linear expansion curve is critical.
Nitrogen in a vehicle tire is a total waste of your money, every argument I have heard for it is based on science in different and non comparable settings.
Some of the main benefits of using N2 as an inflation medium are: higher air pressure retention due to lower permeability than O2 through IIR, NR, and SBR compounds (which leads to improved gas mileage); linear volume expansion with temperature because of nitrogen's inherently low water absorption characteristics; and the expected improvement in structural durability due to
a significant reduction in rubber oxidation (oxidation caused by air from the cavity being forced into the tire carcass)
The characteristic linear volume expansion with temperature because of nitrogen's inherently low water absorption characteristics is no benefit to the average driver because the handling requirements for daily commuting are nowhere near as demanding as for racing; the improvement would be negligible and imperceptible.
AKA Nitrogen will not be absorbed by or commute through the rubber of your tires as fast as air (useful if your storing your vehicle for years), and it won't auto-ignite (not an issue unless your running at high speeds or with huge tires)
You give some good points, but Jeep tires don't often find themselves at 30,000 ft one moment and 0ft the next (where water vapor may condense and cause a 'big' issue) nor are they being used to calibrate temperature dependent systems (refrigeration) where a true linear expansion curve is critical.
Nitrogen in a vehicle tire is a total waste of your money, every argument I have heard for it is based on science in different and non comparable settings.
Wow, I just had College chemistry flashbacks there. Didn't understand any of it then either
JK Junkie
Joined: Sep 2007
Posts: 2,164
Likes: 0
From: Catonsville, MD
......and yet my TPMS has not gone off yet. I keep my tires at 30psi and not one ding. When I used air my TPMS went off every morning. So it works for me and thats all I care about. Well that and the fact that BWI and Washington National Airport and Dulles International Airport and the Naval Academy all keep believing it helps them, if they quit believing then they will quit buying from me...that could hurt financially.
So I guess it comes down to what we each believe.....and thats cool (no pun intended)...
So I guess it comes down to what we each believe.....and thats cool (no pun intended)...
JK Junkie
Joined: Sep 2007
Posts: 2,164
Likes: 0
From: Catonsville, MD
And don't get me wrong....it may not be worth it to some people. Especially if they still go off road in the winter. I went last weekend and re aired with compressed air and had tpms problems until I purged them back out. But I most likely won't go any more till spring so it is worth it to me (that and its free for me)....maybe it is coincidence, maybe it works, who knows.
JK Super Freak
Joined: Apr 2008
Posts: 1,267
Likes: 2
From: Thunder Bay, Ontario
Up north N2 in tires is a great thing for TPMS. You can have some pretty extreme temp changes. You can also have temp variations just by having the tires on one side of the Jeep in the sun while the other side is in the cold shade.