Tire air pressure

[Ram12375]

For those who have E rated tires rated for 80 psi, what psi do you run for daily driving versus towing? I've always had 35 inch bfg ko2's E rated for 65 psi and I ran them at 50 psi at all times. This time around I'm not going with a bigger lift and 35's. All tire choices I'm looking at are 80 psi rated. Would I be able to take the same approach as I did with 65 psi E rated tires and run them at 50 psi ?

 

[Eighty]

Why so high? I run 35’s but only at 40 psi.
If you use a chalk test, you’ll find the best pressure for your setup.

 

[Ram12375]

What is the max psi of your 35's? I think you are saying 40 psi would be fine even if tires max psi is 80

 

[Eighty]

Max psi doesn’t matter unless you’re heavily laden. Proper pressure for the actual load (usually empty) is what matters.

But the answer on my tires is 50 psi. They’re not exactly load-rated tires. Goodyear Wrangler Territory 325/65r18.

 

[Shine006]

I run 45 on my Falken LT275/65r20’s.

 

[Lpsouth1978]

I run my Yokohama Geolandar A/T G015's (E rated to 80psi max) @ 45psi for daily driving and increase it to 55psi when towing my camper.

 

[Falken QA]

For those who have E rated tires rated for 80 psi, what psi do you run for daily driving versus towing? I've always had 35 inch bfg ko2's E rated for 65 psi and I ran them at 50 psi at all times. This time around I'm not going with a bigger lift and 35's. All tire choices I'm looking at are 80 psi rated. Would I be able to take the same approach as I did with 65 psi E rated tires and run them at 50 psi ?

Tire pressure is based on the load of the vehicle and/or the contents it carries/tows. Typically you want to find out what the load capacity is of the factory tires, as your baseline. From there, depending on the size you are using, reference the industry tire inflation chart to find the proper air pressure for your tire size.

Keep in mind that Ram, along with other vehicle manufacturers, based their air pressure on a loaded vehicle (full cab of people + remaining weight up to max stated cargo load, full tank of fuel & fluids).

 

[Talon4U2NV]

I’m sitting at 40psi at the moment with 295/60R20 rubber.


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[cervelo15]

43.6 up front and 41.6 out back for every day driving…and I have th
e BFG KO2s and they are pillow soft at that psi. Of course I had the road force balanced too, so that helps.

 

[Rsone 11]

I have a 22 rebel with a 3 inch Fabtech lift with 35x12.50r18 Nitto ridge grappler and I had to set them to 40 front and rear since the load is F 12 ply which is over kill for this truck but it’s the only load that these tires come in for this size. Crazy to think wrangler guys use these same tires but I guess it’s the cost of wanting that look.

 

[Bt10]

The chalk test is the old way, that still works ok. There is also a formula from reputable tire sources floating around the internet to calculate your psi. It may even be less than 40 on an E range tire unloaded for daily commuting. Based on some answers here, more people should really look into the formula.

 

[Rsone 11]

Anyone running nitto ridge grappler load f 12ply on a new body rebel if so what psi do you have …?

 

[@JC]

Crazy to think wrangler guys use these same tires but I guess it’s the cost of wanting that look.

Just because a tire is rated up to 65psi doesn't mean it has to be inflated to that psi. Your tire psi is specific to your truck's weight/load. I've got Falken Wildpeak AT3/Ws in 35x12.5r17 with a max psi of 65 on my Jeep 392. I run them at 36psi on the street and they handle and ride great.

 

[Ram12375]

I get it now. Thanks for all the straightforward replies to this thread. My posts are usually answered by riddles and questions

 

[Talon4U2NV]

The chalk test is the old way, that still works ok. There is also a formula from reputable tire sources floating around the internet to calculate your psi. It may even be less than 40 on an E range tire unloaded for daily commuting. Based on some answers here, more people should really look into the formula.

Share a link the calculator/formula if you have it, I'm sure a lot of people would use it. I searched but didn't have much luck but it was cut short hunting for it due to life. I'll be hunting when i get free again.

 

[CalvinC]

There are some formulas also in the following document, but here's the procedure which I think is much easier:
(It will take like 5x longer to read this the first time than actually doing it, which is a 30 second affair after acquainted).

Basically, a tire's weight carrying ability at a given PSI varies based on tire size and load range. E.g. the same pressure will not support the same loads across all tire sizes and load ranges.

So the procedure is to determine your required weights, then lookup tire inflation tables to see what pressure to run for any given weight.

Here's a widely used table from Toyo tires, you can use this even if your tires are not that brand, as long as you stick to your size and load range:

https://www.toyotires.com/media/2125/application_of_load_inflation_tables_20170203.pdf

To get your tire's required weight capacity, there are 2 methods:

A) Infer from the factory recommendations:

1. For this you evaluate your driver door placard recommended PSI, along with how you felt about running that PSI when you were on the stock tires.
2. If you liked it spot on, a few PSI higher or lower, ran different pressure front vs.. rear, etc., then take the PSI you liked and look up your original size of tire in the proper load range table. Non-Rebels and non-Max Tow trucks all come with P-metric passenger tires stock, so you'd consult pages 13-19. For example, let's say I liked running 32 psi on the stock size P275/65r18, which is a little lower than the placard instructed. So I look up 32 psi, which shows 2,502 lbs. in this table.
3. Then if I upgraded to an LT tire, I'd find my new tire size somewhere on pages 20-25. (or Floatation sizes on pages 26-27).
4. For example, if I upsized to an LT 275/70r18, then I'd find in the LT tables the row for that tire size, and then in that row I would find the number closest to the 2,502 lbs I got previously. (Note most sizes have 2 rows, 1 for a single wheel and another as if used in a dually... use the "Single" row).
5. In this case, we see a the most similar listing of 2,470 lbs in the column for 45 psi. Since that is slightly below our 2,502 you might be fine with 45, or maybe bump up to 48 or so.
   Sub-note: I upgraded to the stock Rebel tire size and load for this example. So now we can see why the placard pressures on Rebels are so much higher than non-Rebels.

B) Work from your own weights: You might do this if, for example, you are the second owner of the truck and never experienced the original tires, or if you are heavily modified and your daily driven weights are no where near stock.

1. Determine the weight carrying capacity that your tire needs to meet. This isn't so straightforward. As you can see from the stock number examples above, 2,502 lbs/tire would mean the set of 4 can carry 10k lbs, well above our trucks' 7k lb GVWR. And that example's PSI was lower than what Ram recommends running at max capacity. So obviously there is a safety margin engineered into the OEM figures. Therefore, the complexity of this approach is that determining the safety margin to use is on you.
2. If you can weigh your truck do so. Then you can get fancy with weight distribution front vs. rear, especially if towing or completely empty.
3. Once you arrive at a weight for 1 tire, increase that by some margin to accommodate transient loads, like cornering, braking, and bumps - our previous example suggests something like a 50% margin, so there's a baseline.
4. Once you have your weights, the steps are just like above steps 3-5 with the weights you came up with. Find your tire size in the tables, and locate the weight closest to your calculations, and infer the PSI from there.