if want the old fashioned method of working out the best tyre pressure for your own vehicle get hold of some chalk and a foot pump. Put a line of chalk across the tyre and drive around the block. If the edge is worn but not the middle increase the tyre pressure, if the middle is worn but not the edge lower the tyre pressure. I have the same tyres and run them at about 2.2 bar, but my vehicle is heavier than standard with a winch and body protection roof rack etc.