help with my drive tire choice

Not it's not wrong...
http://all-used-tires.com/blog/2011/07/overinflated-tires/

 

And it should have.

 

an underinflated will also wear out the center if you drive at highway speeds. tire diagram's like MNDriver posted is conventional wisdom based on research for car tires mixing around town driving with occasional highway. It's true when turning and manuevering you are putting loads on the shoulders of the tire.

However, centrifugal force increases greatly at 50+ mph vs. typical car driving as well as the additional weight in spin on truck tires. it can also produce a "traction wave". first documented by the airline industry on plane tires.

I mean, if you've ever swung a bucket with water in it to test centrifugal force you know how strong it is. Imagine swinging that bucket as fast as a tire rolling 75 mph, pull your arm off in a second. Then imagine a flimsy tire tread not supported by air pressure. gonna be shaped like a bike tire. Or just go put a couple tires at 30 psi and try it. guarantee you will wear center of tread.

 

No, you're right on. But it's not a recommendation for pressure setting. It's the max load the tire is good for at given pressures. Minor difference, but important. Your correct pressure is somewhere between that and the max inflation.

I used the chart as a starting point. Knowing the occasional bonehead dock hand will overload either my drives or tandems potentially to as much as 40k, I started with a pressure that would carry at least 20k on an axle. Which happened to be at 80 psi on my chart. I didn't like the sidewall flex under a heavy load so adjusted up to 90. I watched the wear and handling with each change.

When I decided which cat's eyes to buy, that actually worked out perfectly. The 90 psi rated ones will shut the crossover at -10%, or around 80 psi. With a flat, the axle is still good for over 15k. I've had a flat under a heavy load and had no problems with the axle the flat was on. Of course I still had to be careful to not do any tight turns and whatnot since that corner was on one tire.

I usually run them at 92-94 for a little margin when it gets cold, and to reduce sidewall flex a little more. My tires wear out evenly enough that I don't need to test with a chalk line. For what it's worth, once in a while when I'm pre-tripping I'll have parked on a hard surface after rolling thru some sand or dust (or chicken blood mud LOL). I look to see that it's picked up or rubbed off evenly across the tread to spot odd wear patterns.

 

On my trailer, I and the previous owner set the PSI at the "K. R. School of trucking" recommend 100 PSI. This promptly destroyed the tires, mostly on the outsides because they had way too much air in them for the weight being carried.

The new set are running at the Michelin recommended 75 (+ 5 cause it's just easier to see 80 PSI) and wearing very nicely. Go figure.

 

Nope.

1) Density. Water and air have different densities.

2) Pressure. The vehicle weight puts pressure on the tire, so the water bucket theory doesn't hold, as the bucket is swinging in free space....

Proper inflation is probably the single biggest factor in tire life, and with 18 of them to check, also the biggest nuisance....

You really have to use an air gauge, as no one can thump a tire and accurately tell you it's air pressure....