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Correct Air Pressure Nitto Terra Grapplers G2 305/55R20

ToyjoHa

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Can anyone tell me the correct air pressure for my new tires? It may not have anything to do with it, but here is the factory sticker... 20210702_101621.jpg
BTW, what does the KN557954 in the lower right corner stand for?
 

brian42

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Can anyone tell me the correct air pressure for my new tires? It may not have anything to do with it, but here is the factory sticker... View attachment 98551
BTW, what does the KN557954 in the lower right corner stand for?
As Eighty said, those are the last 8 digits of your VIN in the bottom right corner.

Your tire load sticker is for tires with a load rating of 113 ('T' is the speed rating) so that's out the window. I'm not sure which model you picked but there are three options for your tire size:

- XL-rated (116 load index with max cold pressure of 50 psi)
- E-rated (121/118 load index with max cold pressure of 65 psi)
- F-rated (125/122 load index with a max cold pressure of 80 psi)

Plenty of advice out there on how to run 'aftermarket' tires, ranging from run them low for a soft ride, run them high for load capacity, and everywhere in-between.

You can do the "chalk test" where you draw a chalk line across the tread, move the truck several revolutions, then look at the chalk line on the tire. If it's evenly worn then you have the "right" pressure for best tire wear. If not then adjust as necessary for even wear (if it's lighter in the center drop a few psi, if it's lighter on the side add a few psi).

Personally I hate tire bulge (I have more sidewall with my 18"rims) and prefer a firmer ride. I run my tires closer to max for load margin, less bulge, and less heat generation (whether that's a factor or not I think so and that's all that matters ;)).

Regardless of what you do you want to make sure the tire load at that pressure will be more than what you need to support the weight of your truck and anything else you want to do with it (haul, tow, etc.).

Here are the ratings you want to make sure your tires add up to being more than:

Front GAWR - 3700 lbs (2wd) or 3900 lbs (4wd)
Rear GAWR - 4100 lbs

The GVWR is 7100 lbs so by making sure that your tires are more than your GAWR you are good to go.

The front tires need to have a minimum load capacity of 1850 (1950) lbs each and the rear tires need to have a minimum load capacity of 2050 lbs each.

I use the Toyo tire load tables when I'm trying to figure out pressure vs. capacity. Based on the tables (attached) you would need to run at least 35 psi to make sure your tires aren't the limiting factor. You could go a little less but 35 psi is the lowest pressure column and I don't know the equation to calculate load capacity for tire pressure (it's not linear).

As far as a safety factor anything over 35 psi and you'll be okay. Anything above that is going to personal preference as far as looks, ride quality, and tread wear.

Just my .03 :cool:
 

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  • Tire Load Tables_Toyo.pdf
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ToyjoHa

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Thank you, they are F-rated. I don't use it for work or hauling other than the 2 city miles to drop the Bennytoon in the Ocean and back.
Wear and the most bang for my buck is what I am looking for especially in the tropical heat of Key West and the 2 to 3 times a month drive to the Miami VA and back. I just did a day trip from Key West to Miami to Ft Myers and back to Key West and the tires read at about 37 leaving and around 40 on the interstates and toll roads, traveling at an average of 79mph. The ride was smooth, responsive, and quiet with 24.6 mpg through the Keys and 17.9 on the faster roads in Miami and to Ft. Myers.
I think the chalk test is going to be my go-to and not play with it for dropping and retr the boat or traveling. Thanks for the advice and the chart.
 

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