I love easy experiments that bring real evidence to endless discussion. I perform them whenever possible. Unfortunately, I don't own P tires but otherwise I'd be happy to run them at 25psi for a while (with due caution). I'm sure cornering would be less stable and mpg would suffer, but what else is it you imagine would happen?

I'm not saying LT tires are bad -- look at my sig. If someone is going to beat up their tires offroad, by all means get some. But I do dispute the common idea that they're the only way to go and are superior to P type tires. P-metric tires generally outperform them on pavement, especially in wet conditions where the water is not deep.

LTs simply have certain performance characteristics that may or may not be desirable depending on application. One important way they're different is the load/inflation curve and it's something worth knowing. The tire load reserve on 4th and 5th gens is generous enough it mostly doesn't create a problem but it could create one on, say, a 3rd gen with the smallest stock tire size offered and then switched over to an LT of the same size with no adjustment in pressure.

As far as the sidewall, here's a small point to consider. Yes, the LT sidewall is stiffer but the deeper tread and thicker carcass mean there is less air volume inside a tire that has the same outside dimensions. The P tire holds more air volume at the same psi. I'd love to do the same deflection experiment on a P tire that I did on the previous page. I'll bet the curve would look nearly identical (please feel free to contribute some experiments along these lines yourself.) Also, I specifically asked the tire engineer about sidewall life, specifying that size, load and (low) psi were the same between the tires and that rough treatment of the tire was not part of the equation. He said he would expect the aired down P tire sidewall to last longer. This is mostly academic and irrelevant for offroading, but it illustrates a non-intuitive point that helps demonstrate why the load/inflation curves can be different between the two.

But the Tire and Rim Association publishes the load tables, not me. If you think they are misleading, write to them.