Tire Pressure for Street 37" Tires

[craq5]

Please post the tire pressure you are running (Street) on your 37's. I have gone round and round on equations, calculators trying to find optimal tires based on load rating etc.... Getting some wild numbers etc....

I would like to know what the consensus is, My GVW is 6080 LBS, running 37x12.5R17, Load Rating D, Yokohama Geolandar. Tire Max Load is 3525 LBS@50 PSI COLD. When I got my wheels mounted by the shop they inflated to 42PSI which I feel is way too high

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[Broncoman7072]

Every tire and wheel combo will be different. You can use chalk or a paint pen to mark the tread. Adjust tire pressure until the mark wears away evenly.

I am running 37x12.50r17 Cooper STT PROs (load range d) on 17x8.5 wheels. 4 door soft top Basesquatch.
Using the chalk method 28-30 psi is perfect for me.

 

[craq5]

Any other experience with 4 door hard top owners running 37's??

 

[kodiakisland]

30psi is rated at 2470lbs, which should be just enough for your weight. Would be a good place to start.

 

[Rkgzx9leftcoast]

As has been mentioned its trial and error, based on Ply/load rating, and tire/rims size. Most tires you can chalk test to get the maximum tread flat at contact point. Just remember , carrying a heavy load in back, or trailer towing will require more air pressure as well for safety. I run mid to upper 30s on mine, usually at least a few pounds less in back tires.
I have Maxxis RAZR at 37s on stock rims.

 

[BlueBronco]

I am running 37x12.50r17 Cooper STT PROs (load range d) on 17x8.5 wheels. 4 door soft top...

Same but running 32psi.

 

[Mainerunr]

This will tell you pretty much what you need based on your stock size and pressure. Note that P-rated tires are derated on trucks (probably applies here too). Going from P-rated 75/55r20 to LT 275/60r20's on my F150 resulted in an increase from 35PSI to 42PSI (at the same size and pressure, LT tires are actually rated to carry less load than P-rated, they just have higher max pressures to end up with higher load carrying capability overall.) I've had to fight with tire shops to get them to put the tires at the correct pressure when changing sizes or type (P to LT), they think they need to use the pressure on the door sticker to cover their ass when they're actually making themselves liable instead.

https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf

 

[craq5]

This will tell you pretty much what you need based on your stock size and pressure. Note that P-rated tires are derated on trucks (probably applies here too). Going from P-rated 75/55r20 to LT 275/60r20's on my F150 resulted in an increase from 35PSI to 42PSI (at the same size and pressure, LT tires are actually rated to carry less load than P-rated, they just have higher max pressures to end up with higher load carrying capability overall.) I've had to fight with tire shops to get them to put the tires at the correct pressure when changing sizes or type (P to LT), they think they need to use the pressure on the door sticker to cover their ass when they're actually making themselves liable instead.

https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf

That's a lot of info!! So i gather from chart below that for single tire load for 37x12.5 I am good for 2835 lbs per tire. For everyday use just take 6080 lbs gvw / 4 = 1520 lbs per tire. So with safety factor range of 25 to 35 would be ideal. Seems 40+ would be overkill unless increasing weight load.

 

[Lanman]

I thought this calculator was pretty easy to use and the recommended psi matched what everyone else was saying in different forums based on tire pressure charts and or their daily driving experience with different tire pressures.

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

 

[craq5]

I thought this calculator was pretty easy to use and the recommended psi matched what everyone else was saying in different forums based on tire pressure charts and or their daily driving experience with different tire pressures.

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

From this calculator about 32 psi. Load rating on calculator only goes to D, mine is E but should be close enough.

 

[kodiakisland]

That's a lot of info!! So i gather from chart below that for single tire load for 37x12.5 I am good for 2835 lbs per tire. For everyday use just take 6080 lbs gvw / 4 = 1520 lbs per tire. So with safety factor range of 25 to 35 would be ideal. Seems 40+ would be overkill unless increasing weight load.

Safety factor for street use is between 1.5-1.6 GVW. If you are rolling at 6K, you need at least 9K weight rating, for highway use. As above in my previous post, 30psi gives you 2470lbs, which is plenty for the safety factor.

 

[kodiakisland]

This will tell you pretty much what you need based on your stock size and pressure. Note that P-rated tires are derated on trucks (probably applies here too). Going from P-rated 75/55r20 to LT 275/60r20's on my F150 resulted in an increase from 35PSI to 42PSI (at the same size and pressure, LT tires are actually rated to carry less load than P-rated, they just have higher max pressures to end up with higher load carrying capability overall.) I've had to fight with tire shops to get them to put the tires at the correct pressure when changing sizes or type (P to LT), they think they need to use the pressure on the door sticker to cover their ass when they're actually making themselves liable instead.

https://www.toyotires.com/media/pxcjubjs/application_of_load_inflation_tables_20200723.pdf

You have to remember P-metric tires are down regulated for use in LT applications. The weight rating on the chart for P-metric has to be reduced 10% for the weight rating in an LT application. So while it may look like they have a higher weight rating at the same pressure, they usually don't after the correct conversion is made for LT application.

 

[jolson1228]

The calculator I used is at the bottom of this article when I went aftermarket.

https://www.calconic.com/calculator-widgets/Tire-Pressure/61a69025fac0dd002a058f3f?layouts=true

It was only 1 PSI high when I ran the chalk test for my setup, but I used the GVWR instead of getting my Bronco weighed so that's probably where it was innacurate.

For yours, I just used the axle ratings from Base/BB because it's pretty close to your GVW. The calculator says mid 20s for your PSI... So yeah, I'd agree that 42 is way too high. I'd drop it down to upper 20s and do a chalk test!

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