Tires: Tire pressures/load capacities, inflation pressure, dunlaps

Question
QUESTION: My F-350 placard requires LT235/85R16E tires at 60PSI. The rear (Dunlaps) tires show a max load rating of 2778 lbs at 80 psi. My font tires (Electra) show 3042 lbs at 80 psi. What would the load rating be at 60 psi? Why is there a difference in the front and back tires when they are the same size?

ANSWER: David,

Look a little closer.  The front tires say 2778 # at 80 psi (dual).  The rear tires say 3042 # at 80 psi (single)

I'll bet they both say both things.

This means that if the tire is used as a dually, then the lower load applies.

---------- FOLLOW-UP ----------

QUESTION: My truck placard recommends 60 PSI, with these tires what would the load rating be at 60 PSI?
Which should I follow the placard at 60 PSI or the tire at 80 PSI?

Answer
David,

Follow the placard inflation.

I hesitate to provide for you the load carrying capacity at the lower pressure, because this is the type of thing that is supposed to be used for design purposes and is easily misinterpreted

BUT

at 60 psi an LT235/85R16 has a maximum load carrying capacity of 2260 # (dual) and 2495# (single).

Please be aware that this does not mean you can actually load the tire to this level without other considerations.  That is why the vehicle manufacturer spends a lot of time considering what tire size and inflation pressure is specified on the placard.

In this case - if you are interested in how much load your truck can carry - you should consult the vehicle manufacturer.  They publish a payload value for each pickup truck and the pressure specified on the placard not only is factored to consider the load in the bed of the pickup, but also applicable factors to ensure a safe operation under a wide variety of driving conditions, including the way the vehicle handles with that load.