That's really sort of a misleading label, at least to me, since a LT tire can be load range C,D,or E, all of which are designed for vastly different pressures. Load range C is generally very similar or the same as a P-metric, a load range D is generally 45-65psi then Es go typically 65-80psi. I have never herd of a load range E with a recomended psi in the 40s. 50s really wouldnt scare me, a lot of tire experts would probably disagree, and say 60 is the minimum others might say 50s is fine on a SUV, I would imagine most would say 46 is too low for a load range E.
Here is debate on a tundra forum about psi on load range e.
http://www.tundratalk.net/forums/tu...e-e-tires-what-tire-pressure-you-runngin.html
It is not as simple as you imply.
In order to determine the correct Tire Pressure (TP) for a LT tire when replacing a P-Metric tire one must first determine what the factory recommended Load Limit is.
In the case of my Land Cruiser with stock P285/60R18 114V tires, the factory recommended TP is 33psi Front/Rear.
One has to then look up on a Tire Pressure/Load Limit table what the Load Limit is for that tire/pressure combination. In this case, the Load Limit recommended by the factory is 2,512 pounds @ 33psi.
When replacing that P-Metric tire with an LT tire, we must first reduce the Load Limit by dividing by 1.1. This means we must find a TP/Load Limit value that is equal to the P-Metric value of 2,512/1.1, or 2,284 pounds.
In the case of the BFG AT T/A E rated tire, the Load Index is 121 (Max Load is 3,195 pounds @ 80psi). Again, referring to the Pressure/Load table for E-rated tires with a Load Index of 121, we find that at 39.3psi that tire has a Load Limit of 2,286 pounds - slightly above what the factory recommends (taking into account the reduction for LT tires).
In the case of the BFG AT T/A D rated tire, the Load Index is still 121 (Max Load is 3,195 pounds @ 65psi). Referring to the Pressure/Load table for D-rated tires with a Load Index of 121, we find at the same 39.3psi that tire has a Load Limit of 2,286 pounds - exactly the same as the same tire in an E Rating.
So the Toyota recommended TP of 46psi is more than enough for either the D-Rated or the E-Rated tire. Probably Toyota are erring on the side of caution and upping the recommended TP assuming heavier loads or perhaps even hoping for better gas mileage - who knows, it is just conjecture on my part.
I am currently running my tires at 39.3psi.
Sorry to be long-winded, but now you have indeed heard of a recommended TP for an E-Rated tire in the 40's - even in the 39's - and the rationale for it.
HTH
