The car can have oversised tires , so when putting them on maximum pressure, you can also experiënce discomfort by bouncing.
I am able to calculate a save lowest pressure for you , but need 100% acurate determined weights on seperate tires best, second best axles, wich is never possible. But give it the best you can , for instance empty weight and the way you load it adn towbarweight and if you use a Weigt distribution Hich.
Also from tires I need the maximum load or loadindex, Loadrange to determine the AT-pressure , but better AT read from sidewall, and if you can find it speedcode.
I hope this is the cource and I can help you .