I've got 31" BFGs on my 98 XJ, my mechanic friend says since they're LT tires I can run them at 40psi for better mileage (it's a daily driver)

Opinions?

 

read the side wall. It will have a MAX PSI rating on it. when your tires are cold you should be about 3-5 psi below that rating. and remember that is a COLD PSI rating. when you drive the gasses expand due to heat and you will get a different reading when hot.

and if you over inflate your tires you will wear out the center section, if you under inflate you will wear out the side tread

 

I checked the tires, they say cold 50psi max

 

then run them at 45/47psi. that is what i run mine at. (different tire but same psi rating)

 

The MAX rating on the tires isn't a guideline of how many PSI you should run. It's just what it says, a maximum.
I think BFG's(A/T's anyway) are rated 50 psi max. I'd be willing to bet not many people run theirs daily at 45-47 psi, according to that 3-5 lower than max theory.


OP, 40 will be plenty fine. You might notice a little more rigid of a ride, depending on what you run now... but 40 is not really that high to worry about uneven wear. If you're concerned, inflate them to 40 and then use a chalk/paint line across the tread to make sure they wear evenly.

 

Thanks for the good info guys!

 

^^THIS!!^^

 

i run my tires at the max also. because i never carry anything that would cause me to worry about tire pressure being too high and the tire blowing out.

my wife has 10 ply tires on her liberty, those v-steel tires. they run at a high pressure, if i remember right. something like 60 or 70. i don't run those at that pressure though

 

yup with my 3-5 rule, my tires contact fine and evenly. nice even wear with all of my tires