I started reading the data book once because I couldn't figure out what Deere was up to putting 18.4R38 * radials on 9600's and then putting 24 psi in the manual, when "everyone" knows that a 1* tire of that size is an 18 psi tire and won't carry the machine empty without a header.

Well, when you read the book instead of just looking at the charts, it was "legal" although only 'just' legal. The cyclic loading and torque-only-to-propel vehicle footnotes make a world of difference in what a tire will carry, and 5 mph does too (although a grain cart better not be loaded to the 5mph chart if I'm running it). Between them they allowed a butt-load more weight to be carried, along with the extra 6 psi.

If you really want to see some 'exceptions' look at creep speed and stationary capacities. IIRC something there is a 150% overload....and I mean 150% overload, as in 'was 10000 lbs, now 25000 lbs,' not just you can carry 150% of what the book says.