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Discussion Starter · #1 ·
i just got 4 new Nitto Terragrapplers tires and they say on the side wall that they can be inflated up to 65 psi. i kno that the only reason they can be inflated to that high pressure is so that more weight can be put on them. the question i have is what pressure should i be running in them. right now i am running around 45 psi. is there some sort of equation or formula that can help me figure out how much to inflate them to, for maximum tire life?
 

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Chalk test, yeah, but I guarantee 45 is too high, unless you're really loaded up with very heavy gear. I have a Jeep with load range E Toyos that can be inflated to 80 psi, and I run them at 28.

My BFG MTs on my X (65 psi max) chalk tested at 35.
 

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From a USMC post a while ago, with a formula that he got from BF Goodrich engineers:
OT=Old Tire
NT=New tire
DS=Door sticker

OT max. load X (DS psi./OT max psi.) X (NT max psi/NT max load)= new tire pressures...
example: 1609 X (32/35) X (44/1709)=
1609 X (.9143) X (.0257)=
1609 X .0235 = 37.8 psi Front...

1609 X (35/35) X (44/1709)=
1609 X (1) X (.0257)=
1609 X .0257 = 41.3 psi Rear
I used this on the Suburban when I upgraded to larger tires and it worked out really well.
 

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It tells you on the little sticker inside the driverside door what tire pres. Nissan recommends based on the weight of the vehicle.
You can adjust accordingly based on driving style and amount of weight loaded in vehicle.
My Bighorn's (D range) have a 50psi max but I run them at about 38 for street driving.
 

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The door recommendation's are for the tires they offer as stock, when you upgrade sizes, load ranges, Ply's, width's it will all change. I called the tire manufacture who has a program that gives you new Tire PSI they ask like year, model, weight, and then tire specifications and then they give you the recommended tire pressure. A BFG AT 285 75 on an 8" wide rim was 42 Lbs. And I find that to be about right as a minimum tire pressure. I'd say the manufacture of YOUR particular tire is best to answer this question, they are the ones that will warranty the tire too.

Also note BFG had me change the rims to an 8" wide rim because they said that 285's need that size rim. And looking at the two mounted and inflated to spec, I could see how the Factory rim caused the tire to Bulge at the center of the tread. Next time I will go with Factory size for better MPG, Weight savings and lower cost fit (Factory rims) And.... larger tires reduce your towing capacity greatly and put more strain on the driveline.

I have the larger tires and rims and wish I had not done that. Bad move, looks cool though. But! In the snow, the factory tire really suck!

MC
 

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Discussion Starter · #11 ·
well i guess i will be deflating my tires a little bit then. Thanks for all of the input on this matter and this is the reason that i love this place. :cheers:
 

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Magic Rat said:
From a USMC post a while ago, with a formula that he got from BF Goodrich engineers:
OT=Old Tire
NT=New tire
DS=Door sticker

OT max. load X (DS psi./OT max psi.) X (NT max psi/NT max load)= new tire pressures...
example: 1609 X (32/35) X (44/1709)=
1609 X (.9143) X (.0257)=
1609 X .0235 = 37.8 psi Front...

1609 X (35/35) X (44/1709)=
1609 X (1) X (.0257)=
1609 X .0257 = 41.3 psi Rear
I used this on the Suburban when I upgraded to larger tires and it worked out really well.
I did the math on my BFG AT KO L/R E and got to 48.5 psi. Do you guys think I should be running that high? I really do not want that high of a pressure and be bouncing all over the roads. I am running my tires at 35 psi.

Any opinions?
 

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That would be way too high unless you have the X loaded full.

Based on the chalk test, my BFG MT's should be running between 33 and 37 psi. which, guess what, would be just about 35psi. :)
 

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I have 285s. According to the formula provided by Magic Rat, I should be running at 37 PSI. With the chalk test, I had to deflate to 30 PSI to have all tread on the road, especially in the back, and with an empty truck. Which confirms what usmc xterra mentioned, and since I'm using the factory 7" wheels. Also the formula by BF Goodrich gives the max load of a tire at a measured rim width ( which is 8" for 285 ) , and by using 7 ' I have a little less max load, but don't know how to calculate it. Regardless, I trust the chalk test, and my truck does not bounce hard like it did on 36, especially that the 285s are LT and load range D compared to Passenger rating for original , so much harder tire.
 
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