Can someone explain this statement in the service manual?

[kookadala]

I’m certain I have similar cautions in the owners manual for other vehicles, something about bumping up the tire air pressure for continuous operation over 75 mph. Most likely has to do with additional heat buildup in the tires during continuous high speed operation. But I don’t recall those cautions recommending inflating to the max sidewall pressure, just adding a few psi above the door placard.

I’m sure not pumping my E rated MTRs to 80 psi

I ran my E rated tires on my F-350 at 80 psi since I had a 2-ton cabover camper on top. Otherwise, never run at max tire pressure rating unless its 35 psi for my Mickey Thompson 35's

 

[LONGJP2]

Keep in mind, most people never cared about tire pressure until cars started indicating when they were 1 psi out of spec.
They went from summer to winter and back to summer without ever checking.

 

[AndyG]

Ain’t that owners manual guideline kinda like telling 88 year old Viagra users not to abuse the product- really not likely to happen anyway.

 

[Steel City 06]

You will actually get better fuel economy on overinflated tires, at least to a point. I've tested everything from 30 all the way to 80 PSI. Beyond about 50 PSI there really isn't much of a difference. I run 45 PSI now (35x12.5R16).

Also, tire wear tends to increase at the extreme ends of the spectrum. So 80 PSI may wear them just as fast as 30 PSI, even if 40 PSI has less wear than 30.