10psi tire pressure makes a difference...

[Wheelin98TJ]

...I seriously doubt that running them at 45 psi is going to reduce the tread life by 40%, or even half that. I've run the tires on my other pickup about 5 psi over the placard number for years and never seen any sign of excess wear along the middle of the tread, which is what you'd expect if you didn't know better.

I agree. I probably could've chosen better random numbers.

Another scenario, $4/gal gas and 40k mile tires reduced to 35k miles.

If you increase MPG from 16 to 17.5 and gas is $4/gal, your cost of gas per mile goes from $0.25 to $0.22857. A savings of $0.02143/mile.

If this makes your 40k mile tires 35k mile tires and the tires cost $1,500, the cost per mile for tires goes from $0.0375 to $0.042857. An additional cost of $0.005357/mile.

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[Jrgunn5150]

Here I am just driving around with no clue what any of my tire pressures are

 

[KevinC]

2) I feel more of the road imperfections in my steering wheel, but no additional wandering, which was my concern. Mojave suspension helps, but I also have a 1.5 inch spacer on the front, due to my steel bumper/winch. I also had adjustable LCAs and camber dialed in when I added the spacer/bigger tires initially, but figured there'd be more downsides to higher pressures.

I'm curious to know how you "dialed in" your camber on a solid front axle? I think you meant castor.

Rubber compounds of the modern era allows better tread wear than what it was 20 years ago. Tire pressure doesn't play as much a part as it did. I wouldn't recommend the maximum psi that you find on the sidewall, but it's not going to kill the tire.

 

[Flanders]

I agree. I probably could've chosen better random numbers.

Another scenario, $4/gal gas and 40k mile tires reduced to 35k miles.

If you increase MPG from 16 to 17.5 and gas is $4/gal, your cost of gas per mile goes from $0.25 to $0.22857. A savings of $0.02143/mile.

If this makes your 40k mile tires 35k mile tires and the tires cost $1,500, the cost per mile for tires goes from $0.0375 to $0.042857. An additional cost of $0.005357/mile.

I think this one is more realistic. The higher inflation pressure saves 1.6 cents per mile. Depending greatly on the assumptions, of course.

Another way to look at it this: If the tires cost $1,500 and the gas for the life of the tires costs $10,000, then fuel cost is 6.67 times tire cost and a 1% increase in fuel economy is a win as long as it doesn't decrease in the life of the tires by 6.67%.

If you're me - and hardly anyone is - you're replacing tires due to age or damage, not ordinary wear. Running tires a little high saves a little gas and costs nothing.

 

[emiddio]

My 2023 ecoDIesel Gladiator door panel tire data spec says 245/75R17 112T; and 36 PSI;
The 112 is the Load Index, and the T is the speed rating;
The stock tires met exactly that spec - 245/75R17 112T;

Looking at the tire data for the stock tires shows max loading of 2469 lbs @44psi per tire;

So the vehicle tire data placard says 36 PSI, but the tire data says max load 2469 lbs @44psi;

The way I think about it is the "Flex" of the sidewall is a constraint that is to not be violated;
The max flex is the flex that would occur at max load, at specified pressure;
A way to model the "flex" is the number of square inches of tire footprint - 2469/44 is 56.11 square inches for the stock tire;

Since the tire data placard says 36 psi - this means the same footprint, 56.11 sq inches would occur with a tire loading of 36 * 56.11, which is 2020 lbs per tire/wheel;

My vehicle data says curb weight is 4989 lbs, or 1247.25 lbs/tire/wheel;

That means I can carry a total of 4*2020 - 4989 == 3091 pounds of cargo before I need to increase my tire pressure above the 36 psi stock pressure;

I replaced my stock tires with LT245/75R17, 121S; Load Index 121, Speed Rating S, and Load Range E tires;
Their max load data says 3195 lbs at 80 psi per tire/wheel;

I was told that to use these LT tires I should run at 49 PSI, not the 36 PSI stock tires run;

The way to see how they come up with 49 psi is to use the vehicle curb weight along with the max load data like I previously did;

3195/80 means max footprint(flex) for the LT tires is 39.93 square inches area at max load, flex;

49 PSI * 39.93 sq in means 1956.57 lbs per tire loading, or 7826 total vehicle weight;
Which is 2837 lbs more than my vehicle curb weight;

The numbers are almost close - 4 stock tires at 36 psi can carry 8080 lbs, and 4 LT tires at 49 PSI can carry 7826 lbs;

I choose to run 39 PSI, 39 * 39.93 is 1557 lbs per tire or 6229 lbs vehicle weight;
6229 -4989 == 1240 lbs of cargo before I need to raise my pressure above 39 PSI;

 

[jjdustr340]

I've always used a temp gun method.
Fill them to what seems good, then go for 5 mile drive. Take temp readings on inside edge of tire, middle of tire, and outer edge. Ideally, they should be within a degree of each other all the way across.
Hotter on the outer edges, tire is under inflated.
Hotter in the middle, it's over inflated.
Either of those is bad as it can lead to premature tire failure and possible injury. (Think Ford explorer of 20+ years ago)

 

[Chaos Theory]

Oh my goodness, I leave for work and come back to people doing quantum physics in this thread... "...if Venus is aligned with Pluto, particle B quarks to the square root of..."

Also some misinformation-- sidewall numbers are not maximum, and again they're LT "E" tires, so 45 is generally within spec, as others have pointed out. Most just don't do that as it's more comfortable at 35, when actually there would be a bit more wear doing that than 45. But again, as others have pointed out, that is negligible.

And yes, I meant castor. The mods were done at Hazzard Fab Works, which I absolutely believe know what they're doing. They tweaked my steering after the spacer lift and 35's were added. What that entails is a mystery to me, I'm not a gear head truth be told. I just write the check.

 

[antwon412]

Do the chalk test. Probably have to do it a couple times with a different loads in the truck depending how you drive it.

That will tell you exactly how much pressure you should run when you’re empty, when you’re loaded up, etc….

 

[Alan SOBX]

I clicked thinking you had aired down to 10 psi and felt like your tires tracked like a tank on sand.

 

[Wheelin98TJ]

...Also some misinformation-- sidewall numbers are not maximum, and again they're LT "E" tires, so 45 is generally within spec, as others have pointed out....

I guess, to clarify... Nitto's I run, an LT "E" tire, are designed to have 45 psi, per the sidewall...

Post a pic of your sidewall. That'll clear up the misinformation.

 

[PuddleJumper]

Oh my goodness, I leave for work and come back to people doing quantum physics in this thread... "...if Venus is aligned with Pluto, particle B quarks to the square root of..."

Also some misinformation-- sidewall numbers are not maximum, and again they're LT "E" tires, so 45 is generally within spec, as others have pointed out. Most just don't do that as it's more comfortable at 35, when actually there would be a bit more wear doing that than 45. But again, as others have pointed out, that is negligible.

And yes, I meant castor. The mods were done at Hazzard Fab Works, which I absolutely believe know what they're doing. They tweaked my steering after the spacer lift and 35's were added. What that entails is a mystery to me, I'm not a gear head truth be told. I just write the check.

Par for the course here man. You'll get use to it.

 

[Flanders]

...The way I think about it is the "Flex" of the sidewall is a constraint that is to not be violated;
The max flex is the flex that would occur at max load, at specified pressure;
A way to model the "flex" is the number of square inches of tire footprint - 2469/44 is 56.11 square inches for the stock tire;

Since the tire data placard says 36 psi - this means the same footprint, 56.11 sq inches would occur with a tire loading of 36 * 56.11, which is 2020 lbs per tire/wheel;

This is just wrong. The area of the contact patch is not load divided by pressure. It isn't even true for something as simple as a balloon. The reason? Pressure on the contact patch is not uniform. Here's a good explanation from Barry's Tire Tech.

The main thing to understand here is that load capacity is not a linear function of tire pressure. That's why we have load inflation tables. Toyo provides them in a pdf here. Falken has them here in html. Note that they are the same. The standard is set by the Tire and Rim Association (TRA) for the P-metric, LT-metric and Flotation sizes and the European Tyre and Rim Technical Organisation (ETRTO) for the ISO-metric sizes.

 

[Zachanadandy]

I have LT-E tires wear perfectly fine for the life of the tire at 50 PSI, which I use for towing at highway speed in the heat of summer. They were getting too hot at 40 PSI, which you could tell by comparing front and back tire sidewalls by touch.

But I leave them at 50 PSI all the time anyhow, for the improved handling. Note that these are stock-ish sized tires, not 35s or whatever, which would take less pressure.

The manual for the older pickup has a chart showing inflation pressures per type of tire, and says to add X for highway in summer and Y for towing. It came to 50 PSI for the LT-E tires.

I've never seen anyone claim improved handling from running super high tire pressures? Improved how? It's gotta ride like a dump truck empty at 50psi but you do you.

 

[emiddio]

This is just wrong. The area of the contact patch is not load divided by pressure. It isn't even true for something as simple as a balloon. The reason? Pressure on the contact patch is not uniform. Here's a good explanation from Barry's Tire Tech.

The main thing to understand here is that load capacity is not a linear function of tire pressure. That's why we have load inflation tables. Toyo provides them in a pdf here. Falken has them here in html. Note that they are the same. The standard is set by the Tire and Rim Association (TRA) for the P-metric, LT-metric and Flotation sizes and the European Tyre and Rim Technical Organisation (ETRTO) for the ISO-metric sizes.

I did not mean to imply that my analysis was an exactly correct model, but useful
as a 1st order approximation;

Your pdf link - to Toyo tires has a graph that is very close to linear, which validates my thinking;
I was not trying to say what the patch area was exactly, but just calculate how the pressure/loading must change to maintain that particular patch area;

Here is my snip of that graph;

 

[JTGuy]

My 37 C BFG KO2s are at 32 cold. Perfect for me. Off road down to 14psi. I will run them on pavement at 14 for a few miles if needed. When they wear out I get new tires . When my tank is empty I get more gas. If .002 cents matter I need to think about owning a Jeep.

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