Scanny,

That will give you your correct minimum pressure, not maximum right?

For stock sized LT tires on the 5th gen 265/70R17 the min pressure is 35psi. That is the min acceptable for an LT tire, will give 7500 GVWR, 3,750 per axle. But there are other reasons to increase tire pressure beyond min load specifications. Increased tire pressure may give increased gas mileage, improved on road handling characteristics which are to be balanced w/ passenger comfort and tire wear characteristics.

The min pressure for the P metric tires is 26 psi which yields GVWR capacity of 8,000 pounds, 4,000 per axle. Again, this meets the minimum necessary to be within the design parameters for this vehicle and tire combination. Toyota recommends tire pressure of 32, not the min of 26 to increase performance in other areas beyond load carrying capacity. Presumably the additional pressure increases gas mileage, provides enhanced on road handling and tire wear characteristics while providing an acceptable compromise in ride comfort.

A good starting point to provide optimum mileage/road handling would be a similar percentage increase from min in the LT tires as the percentage increase in min over P metric tires. 32/26 = 123% over min. 35x 123% = 43psi. That is the equivalent psi in the LT tires.

The problem with that is that LT tires have much stiffer carcasses and side walls than P metric tires and as such don't require as much air pressure increase over min to achieve optimum mileage, on road handling and wear benefits. The optimum is likely be somewhere in between 35 and 43 psi and you will have to determine what feels best for your particular tire/load combination. I suspect that in instances where the same LT tire is offered in both a D and an E rated tire, the E rated tire will require a slightly lower optimal pressure (maybe 1-2psi?).

Thoughts?

David