LT tires need more air pressure.

[scanny]

This is a great, long thread on tire pressure with focus on LT E rated; it's clear that 44psi is advised for highway driving. An interesting question raised here a few times but never addressed very well is what air-down pressure is helpful and safe for certain conditions for specific tires? Obviously there is a wide range of psi that people air down to under different conditions, but does anyone know of manufacturer or tire-engineer developed guidelines? How low can you go and be safe?

For example: LT265/70R17 E rated (highway 44 psi)
Dirt, gravel fire road at 35-40 mph?
Semi rough desert track at 25-30 mph?
Very rough, rolling desert track with some large rocks at 5-10 mph?
Very rough boulder strewn trail at 2-5 mph?
Deep sand at 5-10?

What about P265/70R17 (standard load, highway 32 psi)?

my take on it that tire pressure should be able to support vehicle weight and don't go over maximum tire pressure. So for any vehicle each tire should support weight no less than than 1/2 of the Gross Axle Weight Ratings (GAWR). So if you check air pressure table for your size and type of tire you'll get minimum required pressure to support that weight. This will be for fully loaded vehicle going on high speed in hot weather, i.e. tires get as hot as they can get. For off-road when you drive slow and tires are not warming up from road friction you can lower tire pressure as low as it allows tire to be seated on the rims. I think that without beadlocks you can safely deflate to 20psi on 4Runners. Not sure about E rated tires though, I never had tires over C rated