Here's the deal.... Check the tyre pressure cold. Hit the road for half an hour, stop and check the tyre pressures. You're aiming for a 4psi pressure increase (due to heat). This will give you the right pressure to run for your tyre/axle load and speed combination. If it's greater than 4psi, you need to run more pressure. If less than 4psi, they're over inflated and you need to drop the cold pressure.
This may however not be the ideal pressure. You may for example increase the pressure by a couple of psi for sharper handling or decrease slightly for more comfort. You may also use more pressure at the front to decrease the amount of understeer.
Stiff sidewall tyres such as the BFG will require quite high pressure compared to a road based tyres such as the GrandPuke. A stiff sidewall will generate more heat. The general rule for road based tyres is to not exceed 36psi no matter what. With the 285/75x16 BFG, it's not uncommon to pump them up to 65psi when running fast and heavily loaded.