Tires: min pressure for E rated tires, wild country xtx, elk hunting

Question
I own a 2007 Tacoma that i drive on rough mountain roads a lot for elk hunting, ect..  I recently purchased BFG AT KO 245/75-16 in 10 ply for my truck, and i was told these tires cannot be run below 55 psi (by Costco) which is far from the 29 front/ 32 rear my truck recommends. This tire at 55 psi and my suspension do NOT work well together, I'm getting beat up like crazy on bumps and its too rough to enjoy. Can i safely run these tires at 35 or 40 psi permanently or do i need to find a tire like the Cooper Wild Country xtx in a C rating so i can safely run lower pressure and smooth out the ride (other tire recommendations welcome)? My truck recommends 245/75-16's but i bought it used with 265/75-16's in a 6 ply, it rode pretty good with this setup. The roads i drive have a lot of sharp rocks and i need a tire i can rely on.

Thank You

Answer
Greg,

Your vehicle originally came with P metric tires and you have put on LT metric tires.  These tires behave differently and I do not recommend substituting one for the other - and here's why.

In order to carry the same load as a P metric tire does, an LT metric tire needs to use 15 psi more.  That's because LT metric tires are built more like their big brothers, the over the road truck tires.  They use stronger, and more heavy duty materials - and part of what comes along with that is a brittleness towards flexing.  In other words, the materials are better but they don't tolerate flexing very very.

But your suspension was set up with for P metric tires using using 35 psi.  If you use the same load carrying capacity, the LT metric tire needs to use 50 psi, and that makes the tire much stiffer and incompatible with the spring rate of the springs, the spring rate os the sway bars, and the damping rate of the shocks.

Using an LT 265/75R16 was helpful in that you could use 35 psi and get the same load carrying capacity (bigger tire = more load carrying capacity#

But Costco is wrong about the lower limit for inflation pressure.  I think you can use much lower pressures.  

Here's what I would do.  If you can see your way to buying another set of tires, then you should find a set of LT265/75R16's and use 35 psi.  If not, when you go off road, deflate the LT245/75R16 tires to 35 psi and reinflate them when you get back on the highway #That means you'll need to carry a portable air compressor.)