Posted by John McNerney [172.70.114.11] on Sunday, February 27, 2022 at 09:01:26 :
In Reply to: Re: The answer sounds like less than 40 PSI posted by Vaughn [162.158.166.197] on Saturday, February 26, 2022 at 20:23:24 :
And that pressure probably makes sense if you are running NDT tires on a truck that is carrying a load, or carries one regularly as they generally did in wartime.
Yes, NDT tires have a significant crown, which is why I specifically mentioned that the info I have may not apply to them.
However, ideal tire pressure varies with the load carried. If 40 PSI is ideal for at 9.00 x 16 NDT tire on an M37 when loaded, then something less than 40 would be ideal for the rear tires for a truck running unloaded. I'm sure the military did not count on the typical operator to adjust pressures for empty vs fully loaded runs, so their recommendation was for the worst case. For someone who is running empty almost all of the time, they will undoubtedly get better traction (especially on pavement or hard ground) and better wear characteristics by running less than the recommended max in the rear tires. If I were running NDTs and running empty all of the time, I would not hesitate to drop the pressure a bit below the recommended loaded PSI.
Jason did not mention whether he was running NDT tires or some other modern design. If it's a modern design, like the Michelin 9.00 R16 XL, I would not hesitate to use the "chalk test" to find the best pressure at which to run the tires. I would not rely on the chalk test on NDT tires, however. As you noted, they are not designed to run with a flat contact patch. (This is one of the reasons they are so abysmal for traction on wet pavement.)
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