If I wanted to (finally) calculate the real pressures at maximum van weight capacity would I use this formula for each axle ??
Max load per tyre x 2 (stamped on tyre) = max load on that axle
Max axle tyre load/max rear permissable axle load = ratio
max psi of tyre/ratio = psi to inflate to
So using the details from the westfalia spec sheet for a high top joker
Front axle permissable load = 1100kg
Rear Axle permsisable load = 1300kg
and my Tyre max weight 750kg @50psi
750kg x 2 = 1500kg max tyre load
1500/1100 = 1.36
50psi / 1.36 = 36psi
750kg x2 = 1500kg max tyre load
50psi/1.15 = 43psi
So as I am never going to be running at max weights I should be fine using a small rounding down factor to say 34 fronts and 40 rears?