Tires: Tire pressure - P tire to LT tire, bf goodrich all terrain, bf goodrich all terrain ko

Question
QUESTION: Barry,
I have a 2008 Nissan Xterra, offroad model.  I recently purchased my first set of replacement tires, specifically BF Goodrich All Terrain KO's.  My original tires were P265-75-16.  I used the same tire size for my replacements, but had to move to an LT tire, with an E Load range, 80psi max (only option available in that size#.  So, the new ones are LT265-75-16. My recommended PSI is 35 for the stock P tires. I am lost as to what PSI to set the new tires at.  I called BF Goodrich, and they performed their calculation, and told me that they should be run around 53 or 54 psi.  I inflated to that recommendation, and performed a chalk test, and it appears that the tires over inflated #chalk wore off in the middle).  Does your calculation give the same result? I am not concerned with harshness of the ride.  My concerns are even wear, and more importantly, safety at highway speeds.  Thank you in advance for your help!
Brad

ANSWER: Brad,

I came up with 48 psi, which isn't a lot different than what BFG came up with.

As you may have read, I am not a fan of switching from "P" type tires to "LT" type tires.

I am also not a fan of the "Chalk Test".  It is unreliable as it doesn't consider everything involved with tire wear and varies depending on who performs the test.

---------- FOLLOW-UP ----------

QUESTION: Thank you very much for your help. If I keep the psi at around 48 cold,
should I expect a safe condition at higher speeds (it's an S rated tire) and
even wear?  

Answer
Brad,

Let me explain it this way:

Tires generate heat.  The amount of heat depends on many things, but what is important to this discussion is that inflation pressure has almost a direct correlation to amount of heat generated.

Heat is the tire killer.  So anything you can do to reduce the amount of heat generated has beneficial structural integrity considerations.  Since LT tires are designed to operate under certain conditions - and the inflation pressure is one of those - using the higher pressure is certainly called for from a heat generation point of view.

Wear, especially even-ness of wear, has so many variables that it is virtually impossible to say that doing "X" is going to ensure even wear.

But since you have to use a higher inflation pressure to prevent excessive heat buildup, you may find that roads with uneven surfaces may cause the vehicle to bounce more readily.

This is why I am not a fan of LT tires in place of P tires.