on pavement , dirt or sand? (ice?)
not stock, ???? key point that. if is, its in the manual and door jamb.
if car is stock and tires are not stock then the body tag for pressure will be wrong. (you did it)
there are 2 ways to do this. if not stock
use the tire engineering tables for weight and tire presssure.
bingo , its a fact each maker of all tires have this table !!!!!
WAY 2: (rubber meet the road , LOL)
or use the tire print test..
under pressure tires, cup
over pressure tires, crown, (RTM)
both cause poor pavement traction, especially on ice.
the tire print trick is with chock/ink/paint on the tread?,
roll car , see prints.?
(see the ink test? paint or chock)
http://www.sensorprod.com/news/white-papers/tcp/
see the contact photos?
see photos. is this clear?
http://www.lexusofpembrokepines.com/tires/tire6.jpg