What PSI to run on my 285/75's | Ford Explorer Forums - Serious Explorations

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What PSI to run on my 285/75's

I have a set of Nitto Terra Grappler 285/75's on my lifted 03. I just set them all to 40PSI, I do a lot of daily driving and about to take a couple of statewide trips on them ( ~ 600 miles each trip ) and am curious where I need to set their tire pressure?

The sidewall says not to exceed 65PSI on them. I have about 5k miles on them since new, and they seem to be wearing pretty evenly, they were anywhere from 35-38PSI each before I brought them up to 40.

These are significantly larger tires than stock of course, so don't really have a guide to go by...any input?

Hey bud,

Just curious how you like those Nitto's...I found a killer deal online for some 265/70/17s at $580 and thinking about getting them. How's the road noise/tread looking so far?


i have bigger tires on my Ex too, and i run mine at 40 too, good on the highway,

Do a search for "chalk test" on this site. IMO 40 is way over. When I was running 285/75 BFGs I cannot remember the psi but it was a whole lot closer to 30psi than 40. BFGs may have stiffer sidewalls but not that much stiffer.

While you'll get better gas mileage at 40psi, your ride will be rougher, you'll have less traction in case an emergency comes up, and you'll wear the middle of your tread out long before the rest, necessitating that you replace your tires a lot earlier than if you had them at the correct pressure.... which will negate the savings in mpg you'll get from running high pressure in your tires.

Just a note about the chalk test - it works when you have new tires and even tread. If you've already worn an uneven tread from many miles at the wrong pressure, you'll have to compensate and guess a little.

You can calculate it yourselves with spreadsheet I made.
See the link to topic on this forum
But when you have tires with max psi of 65, they are probably LT-tires and the calculation can give a low answer because of the lot of load they can carry in comparison with normal tires ( P-tires with 35 psi pressure to calculate with and maximum pressure of about 44 to 51 psi)