The presure of the tire is quit complecated.
Our caravan LMC 490 K is allowed up to 1700 kg. (First benshmark)
195 R 14 C 106/104 R
What does it mean?
The benchmark 104 is the load capacity. This means 900 kg. We got two weels so we have 1800 kg.
Tire pressure = 65 psi
Load capacity = 1800 kg
Measured weight = 1680 kg
Tire pressure / Load capacity * measured weight
65 / 1800 * 1670 = 60,66 PSI = 4,18 Bar
It is quite helpfull to own a mobile compressor. I got one from Einhell.