I have a set of dirt grips 36/14.50/20 mounted on some 10" wide rims. I believe the pressure in the tires now is something around 35-40 and they dont seem to be wearing on the side lugs. The load range is D on the tires and I think its a max of 65. I have searched and I have seen its around 40-45 that most people are saying but they were all on a slimmer tire. I know its a big and wide tire but I still want to squeeze as much life out of them as possible. Also if I do a chalk test what it the lowest pressure I can safely run if 40 is still to high? By no means do I want to sacrifice safety.

 

I personally would not run any load range d below 40. 45 would probably be a better pressure. The width is not what counts.

 

The max pressure on the sidewall is 50 not 65 like I said in my first post. Would 45 still be a good pressure? Thanks for your help Kingfish you seem to be the "tire pressure" guy from all the responces to other people that I have seen in my searches. I didnt know if the width would have a effect on the tire balloning in the middle or not. I just wanted to check cause I didnt wanna wear out 1500 dollars of tires any sooner that I have to

 

If it is 50, then it sound like a LR C. For that 40 should be fine. I would not go lower than about 36. Normal for a LR C on an F150 sems to be 38-40. I have had good results with those pressures.

Don't know that I am the "tire pressure" guy, but have had different load range tires on many different F150s, and have had good results with these pressures. Minimum miles I have gotten out of any tire is 40k.

 

I would think that 35psi would be fine for daily driving.

 

the tires are a D load rating...it says on the sidewall...i have the pressure at 40 now

 

Interesting. Normally a LR C is max 50, LR D is max 65, and LR E is max 80. Now they have LR E with a max 65 and a LR D with a max 50. Nothing like screwing with your mind.
What is the max load at 50 on those tires?

 

3085 lb.

 

Then definitely 40 should work, maybe even a little lower. I still would not go any lower than about 35 - 36. Too low and although it would support it you might get too much sidewall flex. Try it and keep a good eye on the tire wear and adjust as needed. It would be good also if after you have it on a while to let us know how the tire wear is at whatever your final pressure is. The more info the better.

 

will do. i have the pressure at 40 now and i will leave it there for a few weeks and see how it wears.

 

Just a update on my tires. I have 40 in the fronts and the rears to 37. The fronts are prolly leaving one half to three quarters of a inch on both sides untouched. The rears were worse thats why I lowered the pressure but im not sure how much if any it helped. I have a 14.50" wide tire on a 10" wide rim and also its on a 20" rim so im thinkin it just might not have enough sidewall to let everything flatten out.