The placard pressures are more than anything else about ride quality without crucial endangerment due to inadequate tire pressure at GVWR. Under inflation is more insidious than over due to heat build up.
The load rating data in weight and pressure are on the sidewall of the tire. The tire would be over inflated if the pressure exceeds the sidewall value.
Page 174 of the owner's displays a label we don't get which would show the inflation pressures needed to obtain the gross weight capacity of the vehicle:
Inexplicably, we get this label on page 172 which tell us nothing about tire pressures other than a "cold" value:
(It should be noted that GM employs only the most expert and talented technical writers and illustrators for their owner's manuals.)
For my Trax LT, I get 948 lbs. As my Hankookies are rated at 51 PSI and 1709 LBS, they're well capable of the GVWR.
However, without what is a load inflation table, for my 948 LBS, if Uncle Joe Bob and my two cousins were passengers, I'd have to SWAGÂą an increase to about 45 PSI from my 35 "cold" PSI for an extended ride.
Theoretically, one could run the tires at the max sidewall pressure full time and increase fuel economy as a result of much lower rolling resistance (with horrible ride quality). In fact, that was suggested by our august gummint leadership during the oil embargo back in '73-74.
All that said, I wonder what kind of fuss the TPMS would put up with for any deviation from the "cold" tire pressure?
Âą Scientific Wild A** Guess