Does anyone know when the tire pressure sensors activate the light on the dash? The door panel says 37psi but the Big-O-Tires that installed the 305/70/17 MTR's said that was too much. He said it could wear the center of the tires out unevenly, however he said I have to run that much pressure because the pressure sensors will activate with only 3-4psi change.

Is this correct? He also put Nitrogen instead of air in the tires (free) and said that helps maintain tire pressure. News to me.

 

I'm not extremely familiar with the Jeep system as I work on GM's, but GM's system generally will not kick the light until there's a 10 psi difference between one tire and the rest. Also, I can program the GM systems to whatever psi you want to run, but I'm not sure how complex the Jeep system is. You might want to call your dealer and ask if they can adjust that for you. Nitrogen is just alot more stable than compressed air and it fluctuates way less with temperature variations. A cold tire could read 30 psi, then drive it 30 miles and it might read 37 psi. Also I think it's denser than air, so it takes longer to leak out. Tire pressure sensors also seem to be affected by altitude and most of the time they read 4 psi lower than actual at my dealership (9,000 ft.)

 

Your stock tires were filled with Nitrogen.

 

This is correct for the Jeep as well.

Set the pressure on all four at the same time and the system shouldn't give you a problem.

 

Thanks for all the input. I will try calling the dealer. I want to run the proper tire pressure but not trigger the light. I will try asking the dealer (good luck) to see if they can give me some answers. the tires cost $1,810 OTD...OUCH I don't want to wear them incorrectly for that price.

 

The systems usually have a set psi and once it drops 10 psi below that set psi, it'll kick a light. I can adjust that psi for GM's, but I don't know if the Jeep system is capable

 

there's alot of discussion about the TPMS on these boards, alot!

I have my 35's set at 30psi (including the spare) and the TPMS light still comes on. I deal with it for now but plan on buying new sensors or getting the old ones flashed if I can find someone to do it.

As for your proper inflation psi, you can chalk test. Draw a line across your tire and go drive a little. If it wears on the sides your under inflated, if it wears in the middle your over.

 

The dealer was able to use some scan thingy that he hooked up to each tire and set mine at 28psi (he said that is as low as he could go. I run mine at 32 with no problem.

 

The owners manual tells you to check the placecard on the drivers side door for recommended tire pressure. Most are 35psi. The problem with that is, if I set my tires to 35psi cold, then once I start driving, my tires build up to 37 or 38psi. That is way too much for my tires.

My light comes on at anything below 33psi (exact same on my wife's Pathfinder). Ambient temperature affects this. When the weather gets cold, your tires loose pressure and they do not build up enough while driving as in the heat (summer months). My tires are set at around 32psi which builds up to around 34/35psi once warmed up (driving). The best way to tell what pressure to run your tires at is the chalk test. Other then that, your pressure sensor goes off once ANY tire drops below a certain psi, not when there is a 10psi difference between tires. Also, using Nitrogen will cure your problem of loss of psi when cold. Aircraft use Nitrogen in their tires for that exact reason.

 

Nitrogen is superior to standard compressed air because it is an inert gas with the most notable factor being that it does not expend or retract under normal pressure and normal daily temp changes. On aircraft we use nitrogen in all of the tires as well as the entire pneumatic system because it is so stable. When I fill up the tires on my jet I put them at 300 – 310 PSI and if they were filled with air I am quite certain that with the pressure and heat caused by landing they would explode or it would at least severely weaken a standard aircraft tire. Nitrogen is good to run in any vehicle tire but I would imagine it a bit impractical to run in vehicle that needs to air down and back up on a regular basis. - KY