PSI Tire pressure recommendation

[Chasm]

https://tiresize.com/pressure-calculator/

^^ This is the way.

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[yoda13]

35 is the sweet spot for me.

 

[ShadowsPapa]

^^ This is the way.

That site is a bit deceiving in that they keep talking about maximum load capacity.
You can change tire sizes and not change the maximum capacity.
What should be talked about is the load you are currently carrying and how the same PSI working on a larger footprint changes things.

The contact patch is not THAT different from one tire size to another, within reason, but that's where any variance is.

It really depends - if you go from a Sport 31-32" tire up to a 35 that's say 12" across, you have drastically changed that contact area and thus the PSI required to support the exact same vehicle.
I changed the width of my tires on my Overland and that dropped the PSI 2 pounds to get the SAME weight carrying ability.
The door sticker was 38 - 38 was too much in the new tires.
I ran 36 unless towing, otherwise, I had wear issues.
Running at 34 also caused saw-tooth patterns on the outer tread edges - a sign of LOW inflation.
The numbers on my wife's JLU are different from my JT - even with similar tires.
It's not about maximum capacity as that article keeps talking about - it's about how much weight is there now.

GENERALLY SPEAKING - when going wider tires, in decrease pressure.
Tall tires by a fair amount - 32 to 35, you decrease pressure.
That's assuming other things are equal.

 

[biplaneguy]

OEM size tires... Use the pressure on the door sticker and adjust basis on how it feels when driving. Larger tires... Do the chalk test and adjust based on driving.

With Mojave takeoffs I shoot for 33 and don't freak if it goes higher on a sunny day or the highway.

 

[ShadowsPapa]

don't freak if it goes higher on a sunny day or the highway.

No kidding. That's totally normal. That's why you do COLD PRESSURE CHECKS.

 

[Sandman 4x4]

Basically rule of thumb is to know the curb weight, the look at the sidewall weight rating at max psi. Multiply that time the 4 tires holding up the vehicle, then subtract the curb weight. If you are running LT tires with more than 4 ply, then you have enough tire for over twice the curb weight. If so start at half the max psi, then run down the highway enough for running temp. Then check the psi, if the heat has raised the psi more than around 8, then you need more psi, then try again. That’s only for oversized over rated tires, not stock size and weight rating.

 

[Dougstdig]

OEM size tires... Use the pressure on the door sticker and adjust basis on how it feels when driving. Larger tires... Do the chalk test and adjust based on driving.

With Mojave takeoffs I shoot for 33 and don't freak if it goes higher on a sunny day or the highway.

I attempted the chalk test on my 37x12.5’s and it was a joke. Drove me nuts. I forget where I got the information. It may have been off of the graph but based on the new tire white rating, the ideal pressure for me was 29 psi and I ended up bumping it up to 31.

if I use the methodology in the door jam of my 08 Dodge ram because the front end is so much more heavy with a diesel motor and the 12,000 pound winch, though not to the extreme difference as in the Dodge I should be running at least a pound or two heavier on the front

 

[ShadowsPapa]

I attempted the chalk test on my 37x12.5’s and it was a joke. Drove me nuts.

Mine checked fine at a very large range of pressures. I gave up and called the company.
Some tires just don't do well with that method. It's hit and miss (but don't tell the chalk test gods that, they'll say it works perfect every time)

 

[biplaneguy]

Some tires just don't do well with that method. It's hit and miss (but don't tell the chalk test gods that, they'll say it works perfect every time)

No, it doesn't work all the time and it's not precise, but it's a room to use in the absence of other information... which is why I said "adjust based on how it feels when driving." It'll usually get you in the ballpark.

 

[Chasm]

I should be running at least a pound or two heavier on the front

I run "skinnies and fats" on my Fairlane, so added to the large weight distribution difference I have to have a 6-7 lb difference.

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