You may check the tyre pressures from the body near to the left-side door. Open the door, you would see a tag on the connection between the door and the body. The data of my car on it is 2.1(f) and 2.3® under the normal load and 2.1, 2.8 under the full load. By the way, I have been able to do the 600+ miles when I always stick to the speed under 75MPH.