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Another thread about tire pressure

TallDude

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I set my JLUR XR pressure to 35 cold. They were at like 38, which felt too high. I might try 33 next.
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azjl#3

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that unused part of tread, is used every high speed corner here in the mountains.
 

Jtphoto

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While pulling my 2024 JL XR with 35s into the garage, I noticed that only the center portion of the tire is making contact with the ground as you can see in the picture. Currently the low pressure sensor says to inflate my tires to 37. I have them inflated to 34. This tells me that I'm still running too high of pressure and should probably drop it to around 32 or 30. Searching on the forums it seems like most people with 35s are running around 32. Does this look like too much pressure? And if so, what's the easiest way to change the low pressure warning threshold.

Thanks!

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Even 32psi is too high for those tires. I had mine down to 26psi.
 

Jtphoto

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You do realize your entire tread is not supposed to touch the ground right?

I mean you can drop your PSI if you want, but your tires going to wear out quick as hell!

Only time I would recommend driving with lower PSI on the streets is if there's snow on the ground or ice. Otherwise there's really no point. You're just wearing out your tires quicker.
Running too much pressure (that gives you that pattern) with prematurely wear out the center portion of you tires. It’s also dangerous in crappy road conditions. Get you a tread depth gauge and measure for your self. I measure my tread depth every rotation and I can tell you running 26-28psi in a 35” tire will wear exactly like it is suppose to. Running any higher and you wear them out faster.
There are all kinds of tire pressure/weight formulas out there and I’ll guarantee you won’t find a single one that will suggest over 30psi for a 35” tire on a 5000lb Jeep. Tread pattern on ground is determined by pressure vs vehicle weight.
 

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Tire Maximum Pressure is the maximum air pressure the tire can handle. To calculate the recommended tire pressure, you divide the axle weight by the tire maximum load, and then multiply that by the tire maximum pressure.
ie
- Jeep axle weight (weight on each tire) 5,000lbs /4=1,250lbs
- 35” tire max weight 3225lbs
- 35” tire max pressure 65psi

1250 / 3225 = 0.3875969

0.3875969 x 65 psi = 25.1937psi

If you have a RAM pickup that weighs 7000lbs it would look like this with the same tires.

7000 / 4 = 1750lbs
1750 / 3225 = 0.54263566
0.54263566 X 65psi = 35.2713 psi

Check this formula with the figures on your stock 255, 265, or 285 tires.
 

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All depends on what you are trying to accomplish. Long tread life, MPG, traction, comfort. I like low thirties cold unless I’m offroad.
 

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You do realize your entire tread is not supposed to touch the ground right?

I mean you can drop your PSI if you want, but your tires going to wear out quick as hell!

Only time I would recommend driving with lower PSI on the streets is if there's snow on the ground or ice. Otherwise there's really no point. You're just wearing out your tires quicker.
Finally some one said it.
 

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Running too much pressure (that gives you that pattern) with prematurely wear out the center portion of you tires. It’s also dangerous in crappy road conditions. Get you a tread depth gauge and measure for your self. I measure my tread depth every rotation and I can tell you running 26-28psi in a 35” tire will wear exactly like it is suppose to. Running any higher and you wear them out faster.
There are all kinds of tire pressure/weight formulas out there and I’ll guarantee you won’t find a single one that will suggest over 30psi for a 35” tire on a 5000lb Jeep. Tread pattern on ground is determined by pressure vs vehicle weight.
I in fact have two tread depth gauges. One in my wife's Subaru and one in my Wrangler. Both of our vehicles have extremely even wear and I've been running 35 PSI in my 32" mud terrains for the last 2 years. The wife Subaru runs about 35 psi as well in her 29" AT tires.

You should read up above. Tires aren't made to be running around flat foot, they design them with a rounded tread for a reason. You should definitely be asking yourself why have they designed all DOT approved tires that way? And also you should be asking yourself, if everyone is doing it wrong, why isn't everyone trying to fix it?

Hint: It's because everyone's not doing it wrong. Your tires' supposed to have a little bit of a bow to it.

However when talked about PSI, that depends on the tire. My current tires are highway terrains, 235/80r17s, they have a 10 ply side wall, they are designed to be run on Hotshot pickup trucks, In many cases in dually format... They run comfortably at 42 PSI.

Again to assume all tires are the same is just a little bit wonky of an idea. ;)
 

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Finally some one said it.
And I’ll say it again read up on it. Yes Some tires are made to run on the crown but most aren’t.
If you run enough miles and tires you will find out for yourself. The bigger the tire you get the less pressure it requires because it has more air volume.
 

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I in fact have two tread depth gauges. One in my wife's Subaru and one in my Wrangler. Both of our vehicles have extremely even wear and I've been running 35 PSI in my 32" mud terrains for the last 2 years. The wife Subaru runs about 35 psi as well in her 29" AT tires.

You should read up above. Tires aren't made to be running around flat foot, they design them with a rounded tread for a reason. You should definitely be asking yourself why have they designed all DOT approved tires that way? And also you should be asking yourself, if everyone is doing it wrong, why isn't everyone trying to fix it?

Hint: It's because everyone's not doing it wrong. Your tires' supposed to have a little bit of a bow to it.

However when talked about PSI, that depends on the tire. My current tires are highway terrains, 235/80r17s, they have a 10 ply side wall, they are designed to be run on Hotshot pickup trucks, In many cases in dually format... They run comfortably at 42 PSI.

Again to assume all tires are the same is just a little bit wonky of an idea. ;)
Actually 35psi in 32” tire is the equivalent to around 26psi in a 35” tire on the same vehicle. Smaller tires take more pressure to lay the same due to less air volume. Even Toyo tires has a massive chart for this.

Here’s a link to the Manufacturer Toyo with a complete inflation chart.
https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf
 

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2023 High Tide- I find anywhere from 32 to 38 psi to be best for my very mixed driving. Anything over 38 psi and the car starts getting a bit jittery over highway potholes/expansion joints, etc.

Anything under 30 psi and I can definitely feel the tire flexing and grabbing on corners.

Don't care about chalk tests and the like. The only consideration is how the car performs for me.
 

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While pulling my 2024 JL XR with 35s into the garage, I noticed that only the center portion of the tire is making contact with the ground as you can see in the picture. Currently the low pressure sensor says to inflate my tires to 37. I have them inflated to 34. This tells me that I'm still running too high of pressure and should probably drop it to around 32 or 30. Searching on the forums it seems like most people with 35s are running around 32. Does this look like too much pressure? And if so, what's the easiest way to change the low pressure warning threshold.

Thanks!
I know this doesn't answer all of the question. But have you tried inflating the tires to 37 psi just to reset and turn off the light, then deflate them back down to 34? The reason I ask is if 37 psi is the required pressure, I wouldn't think 34 psi would be low enough to trigger the light. I would suspect that at some point in time one or more tires was reading lower than 34 psi which triggered the light originally. And once triggered it will not go out until you go all the way back up to 37. But you could then go back down to 34 without setting off the light.
 

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Tire Maximum Pressure is the maximum air pressure the tire can handle. To calculate the recommended tire pressure, you divide the axle weight by the tire maximum load, and then multiply that by the tire maximum pressure.
ie
- Jeep axle weight (weight on each tire) 5,000lbs /4=1,250lbs
- 35” tire max weight 3225lbs
- 35” tire max pressure 65psi

1250 / 3225 = 0.3875969

0.3875969 x 65 psi = 25.1937psi

If you have a RAM pickup that weighs 7000lbs it would look like this with the same tires.

7000 / 4 = 1750lbs
1750 / 3225 = 0.54263566
0.54263566 X 65psi = 35.2713 psi

Check this formula with the figures on your stock 255, 265, or 285 tires.
Thank you for posting this formula. I have seen it before on another Web site but forgot about it.
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