Hey guys, this is a tire pressure question on a different end of the spectrum. I searched and the only pressure related threads I have found are for those moving from the stock "P" rated tires to either load range D or E.

I recently purchased a set of P285/70/17 Terra Grapplers. I decided to stay with "P" rated tires because I cant justify the extra expense/ rough ride of the D or E rated tires when the P rated will handle whatever little I haul with ease. Besides thats what came with the truck.

My question is, the recommended (door placard) pressure is 35 psi. Most passenger tires I have dealt with run a max psi of 45. The Geolandars on my wifes truck max out psi at 51. Fine and fine, I typically run 5 psi over door placard recommendation and have been golden doing so. These new Terra Grapplers have the same weight rating as stock passenger tires, except the max pressure is 35 psi to haul that same weight. What do I do now? I dont want to exceed the recommended pressure, but dont want to ruin the center of the tires either. I am running 35 psi all around for the time being until I can moniter wear patterns. Any suggestions? Will running less then 35 psi harm these tires as well?

 

The only time I pay attention to the tire pressure settings is when I use oem tires.
P rated tires will not handel the same psi settings as 6 ply 10 ply tires, your ok running 35 psi ( psi settings on your new tires )

I find p rated tires on a 1/2 ton ride like a lumber wagon and are under performing tires on trucks that brag abought higher payload, tow rattings, ect.

 

Go with the door placard. I've been doing that for a long time and I regularly get the rated mileage or a bit better and that was when ALL my driving was stop-and-go city traffic.

 

Same boat I'm in with my Jeep Grand Cherokee. My stock soccer mom tires were max 42 psi and I ran them at 36 (door said 35).

I installed a 2" lift on the Jeep and went to P265/70/17 Terra Grapps with a max of 35. Because I live in the deep south and it's hot most of the year, I don't like to run a tire at full cold PSI so there is a little bit of a ceiling for expanding air molecules when the tires get hot. I have run them at 32 psi since I put them on. Only exception is that I've air'd them down to around 22-24 a couple times when fishin' in the slop of the south Georgia swamps when I've taken the Jeep and not the truck.

I think they handle fine at 32 psi, and with about 18k on them now, there is still no noticeable sign of wear yet...

 

if the max on the tire says 35psi, then run 35psi, if you go any higher you increasing the risk of tire failure

 

That is why I am a bit leary about running them at max pressure cold, being from south Louisiana it stays extremely hot here. I adjusted them to 35 psi just after having them installed. My dad passed away a short time before I made my first post about it and I am currently 275 miles into a 520 mile trip to his house near Huntsville, AL and they seem to be doing fine. I will check for wear when I return home which will put around 1300 miles on the tires since installment with pressure @ 35 psi.

 

NEVER run a tire at max pressure unless you want a bare line running around the center of the tread AND tire failure.

 

where is that dang chart for calculating changes in tire pressure in correlation to changes to tire size given a vehicles weight...fumbles around looking through old files...dang it...i'll have to get back to ya on that one

unless someone here knows what I'm speaking of and has it handy

 

This is the problem I am facing and the reason for my posting. The pressure on the door placard is 35 psi which IS the max psi for the tire. A chart to use as guidence would be most helpful. As leary as I am of running max psi, I am also leary of running too little psi.

 

I was wondering about that. I would've thought that any tire sold these days would have a max pressure above 45 psi. My Bridgestones show a max of 44. Are the Terra Grapplers some sort of off-road only tire?