Low tire pressure?

[GinaC]

Hello all, since this is the first winter I've not been able to use my garage, I'm wondering what's going on.

The other evening I went out and it was -4 outside. My tire pressure lights came on, and they were at 20. About ten minutes into the trip they were at 30. I have the stock 33 mud tires that came with my Willys.

This evening it's 24 degrees and they're now at 31. The dash is telling me to inflate them to 37.

Is this normal, and should I inflate them to 37 tomorrow? Am I going to damage something riding around like this?

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[roaniecowpony]

Hello all, since this is the first winter I've not been able to use my garage, I'm wondering what's going on.

The other evening I went out and it was -4 outside. My tire pressure lights came on, and they were at 20. About ten minutes into the trip they were at 30. I have the stock 33 mud tires that came with my Willys.

This evening it's 24 degrees and they're now at 31. The dash is telling me to inflate them to 37.

Is this normal, and should I inflate them to 37 tomorrow? Am I going to damage something riding around like this?

Air changes volume with temperature. If it's confined as in a tire or tank, it will change pressure.

 

[3TV]

With the stock 33s I would set cold pressure at 30 psi. If you have access to an air compressor so you can set the tire pressure before your Jeep is moved on a cold morning, that would be easiest. It is normal for pressure to drop as temperature goes down and increase as temperature goes up. Something to do with thermodynamics, or some other law of physics. {edit} see above.

 

[GinaC]

Air changes volume with temperature. If it's confined as in a tire or tank, it will change pressure.

I am aware, but you didn't answer my question!

 

[Deleted User 38384]

Hello all, since this is the first winter I've not been able to use my garage, I'm wondering what's going on.

The other evening I went out and it was -4 outside. My tire pressure lights came on, and they were at 20. About ten minutes into the trip they were at 30. I have the stock 33 mud tires that came with my Willys.

This evening it's 24 degrees and they're now at 31. The dash is telling me to inflate them to 37.

Is this normal, and should I inflate them to 37 tomorrow? Am I going to damage something riding around like this?

So if you weren't aware already. At a standstill the TPMS sensors don't work very well. They just give you a general idea of what it thinks they're at.

Next time you start your Jeep, have it on the TPMS tire sensor screen before you start to drive, and I'm telling you from experience, you won't make it more than a block or two before It adjusts and tells you the actual tire pressure.

Actually about to head out right now. I will give you a video here in a about an hour, considering upload times and such.

 

[3TV]

Hello all, since this is the first winter I've not been able to use my garage, I'm wondering what's going on.

The other evening I went out and it was -4 outside. My tire pressure lights came on, and they were at 20. About ten minutes into the trip they were at 30. I have the stock 33 mud tires that came with my Willys.

This evening it's 24 degrees and they're now at 31. The dash is telling me to inflate them to 37.

Is this normal, and should I inflate them to 37 tomorrow? Am I going to damage something riding around like this?

20 psi is a bit low for an every morning thing and I wouldn't recommend it. See my other post for pressure recommendation.

I was in Moab last week and had set my 39" BFGs air pressure at 11 psi for an afternoon trail ride. The next morning was cold (late November), so when I started the Jeep they were at 7 psi. I wasn't particularly worried about 7psi on that cold morning because as Tredsdert says, the initial TPMS sensor reading is usually wrong. By the time I left the campground the TPMS sensors said 9 psi, which was likely the real pressure. I had about 7 miles of pavement to run before getting to the trail, so I left them at that pressure, knowing the pressure would come up with some highway miles. Sure enough, pressure was up to 10 psi by the time I got to the trail, and up to 11 psi again at the end of the day.

 

[jadmt]

you will not damage anything...if the light bugs you air them up to 37psi

 

[Rhinebeck01]

@GinaC

This is typical to see... the norm lets say .... no issue to worry about.

In your locale, in the Winter months, you need to keep all 4 on the ground tires inflated to 35# psi or you will have on going issues with psi low warnings like you are experiencing.

Now you need to inflate all on the ground tires to 37# and drive for say a mile until the psi warning goes away.... Then wait until tires are cold and deflate all on the ground tires to 35#.

Keep at 35# until warmer weather comes and then you can run lower psi.

 

[Rhinebeck01]

With the stock 33s I would set cold pressure at 30 psi. If you have access to an air compressor so you can set the tire pressure before your Jeep is moved on a cold morning, that would be easiest. It is normal for pressure to drop as temperature goes down and increase as temperature goes up. Something to do with thermodynamics, or some other law of physics. {edit} see above.

@3TV
In her locale (Vermont) 30# psi will not be high enough!

If she set to 30# psi, then every real real cold morning she will see the low pressure warning.

To get rid of the low psi warning..... She now has to inflate all on the ground tires to 37# (psi on the driver's door placard) and then drive a mile or less until the warning goes out. Now, she drives the JL home and lets it sit overnight.

In the morning when tires are cold, she deflates all the on the ground tires to 35psi.

Now, on those cold mornings when the psi drops in her tires the psi will not drop low enough to set off the psi warning .... (because she had set psi to 35#)

In Summer time when warm temps come she will inflate to 32 psi...

 

[roaniecowpony]

I am aware, but you didn't answer my question!

Sorry, but I have no way of knowing how much you know.

Since you know it goes up and down with temperature changes, my approach is to get the tires up to what I would normally call a regular temperature, by driving a routine route. Then I would fill them to the desired pressure, before they cool down. Then I would check them when they are cold again in the morning. This would give me both the morning pressure before driving and the "normal operating pressure" after driving the normal routine.

 

[Deleted User 38384]

@GinaC

I don't know if this necessarily answers your question, my Jeep has never been in negative 4° weather. But I can only imagine that normal operating temperature for warmed up tires is probably the same everywhere, So if you have a significantly lower outside temperature, the difference between the outside temperature your Jeep will achieve sitting out overnight and the normal operating temperature once the tires warmed up would be quite extreme I would imagine.

That being said, here's some nuances of the TPMS sensors on our Jeeps:

 

[AKLespaul]

I got a Tazer to get rid of TPMS and the auto start stop. I drive on square tires for a few miles at -40 until they warm up to be round again. No damage at all. TPMS would be all up in my face with issues at those temps. I air down in the winter to 20 psi and 35 in the summer with MT Baja Boss 35's.
The stupid nanny features have killed all common sense people have had learned.

I know AK is not VT, I used to be at Blue Seal grain in Jay and go to Jay peak every week... I have it way better in the winter now.

 

[calemasters]

I took physics.

 

[GinaC]

Thanks so much, everyone!

I was really getting worried because this was such new territory. I'll go fill the tires to 37 tomorrow and hopefully my new Jeep will come in before I have to think about it again.

 

[Kracka]

Someone didn't pay attention in high school...

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