Right now on my truck i have 265/70/16 michelin ltx m/s tires. im upgrading to 285/75/16 bgf AT's. The truck door said 32 psi in the front and 35 psi for the rear for the stock tires. But ive seen some threads where it says that Lt as opposed to p metric tires need to be run at different pressures. So what should i set the new tires at? I do mostly highway driving.

 

Those are either load range D or E tires. If load range D (max 65psi) I would run them at about 44. If load range E (max 80), I would run them at 48-50. Definitely do not run them at 32 or 35.
Yes there is a difference between P series and LT tires, and between the load ranges.

 

thanks for the info. They are load range D. Why the need for more pressure?

 

Higher max pressure. Tire will handle more weight, but does it at a higher pressure. Max on a p series tire is 35psi or 41 for an XL P series compared to 65 for a LR D. P series will handle approx 2000-2200 at 35. Your LR D will handle 3300, but at 65psi. At 35 that tire would be at about half its load carrying ability. That is below your trucks GAWR.

 

ok. However i dont haul anything. All i do is drive highway and some city miles. So do i really need the higher pressure for increased load carying? Or am i missing the point?haha. Im not new to cars or trucks but i am new to these specifics like gawr etc. Thanks

 

Don't forget the front is heavier than the rear sitting still and closer to GAWR when unloaded. Also when accelerating, you get a weight shift to the rear. Same going uphill. By having it set for near max GAWR, you don't have to deal with changing pressures when you do carry something and you will not get excessive tire wear. Also helps with cornering as the tires don't tuck under so much. Running at max pressure would definitely be overkill and wear the tires out early. But 38-40 is what Ford recommends for the F150 with LR C and those vehicles with LR D, higher. Some years ago I had a set of LR E tires and ran them at 50. Good tire wear, and no other problems.

 

Ok. THanks for the help

 

Where/how do you find out what pressure is correlated to what load range?

I have a set of Cooper Discoverer's on an 03 Exp (4.6l) and have them set to 35 psi, according to the door jamb sticker.

How do I check to see if I am running them at the right pressure?

Thanks,

John

 

I went to the Cooper site to look. Or you can look at the tire. It will say as an example either P265/70R17 or LT265/70R17. If an LT it will have on there Load Range C, D, or E. As for the pressures, I have had the different load range of tires and these pressures are what I have found them to work at on an F150, or what Ford has put on the door stickers for either P series, or LT series tires.
Also as an example, my truck came with LT load range C tires with a door inflation of 40. If I were to switch to P series, not that I ever would, I definitely would not want to use 40, as the max on the tire is 35 unless it is an extra load.

 

With out starting a new thread, can someone please tell me the psi on the Nitto Terra Grapplers for a 325-60-18 for an 05 screw 4x4? I searched but could not find anything. I dont know the load range but the tire is an LT. The wheels are Helo maxx 6 18x9. Thanx in advance.

 

Per the web site, that is an LT Load range D tire with a max of 65. I would start at 44-45 and keep an eye out for abnormal wear etc.

 

I really appreciate it, thank you.