How much pressure to inflate on tyre 285x50x20 of Chevrolet Suburban of year 2003?

Pressure should be equal if all tires are the the same size in my opinion. You could look at the decal on the door post for the factory recommendation and compare it to these non factory sized tires.

Thanks for your quick reply. But unfortunately I have nothing written on my door .But if you could help me regarding the exact pressure in tyre 285x50x20 .Or about for Chevrolet Suburban LS2500 of year 2003 that would be great

On the driver's door post near the latch not on the door itself. If it were mine I would try 40 - 45 psi. Look at the tire sidewall and find the maximum inflation pressure. This is the maximum cold inflation pressure so do not exceed that.

It says it on the tire

The "recommended" inflation pressure is NOT on the tire.