|"tire-pressure is calculated and I have the formula"|
I once got hold of the formula that is used in Europa for decades, and in America since 2006 for normal and extra-load tires.
Worked them out in spreadsheets. cant place links yet in my first post, but can say that if you drive with only driver and 1 passenger and a little load, that you can savely go lower with the pressures, most rear lower then front even. But for this you have to know the actual loads on the tires, best way is to weigh it per axle or even better 4 points weighing with the loads you want to use .
If I earned my 6 participation points, I can give the link to my public map of skydrive wher lots about tire-pressure calculation, also in English.
What you need is the loads on the axles , for maximum loaded the Gross axle weight ratings are used in the formula ( GAWR) and of the tires the maximum load and reference-pressure ( this is not the maximum pressure printed on the sidewall). If it is stated "max load xxxx lbs/kg AT yyy psi/kPa" then these are always the pressure and max load you need in the formula.
Normal car tires ( P tires or A-load) have a reference pressure (further Pr) of 2.4 bar/35psi for american tires. Extra-load 2.9bar/42 psi .
And on those tires only the maximum pressure is printed mostly.
Will stop now, google for jadatis and you mayby find other posts where you can link to my skydrive.
Greatings fromm Holland