Just a thought...I found it interesting that the 5th Edition of "Aerodynamics of Road Vehicles" has the following footnote (21) on page 186.
"Every tire has a rated maximum operating pressure that is imprinted on the sidewall (typically specified in kPa, e.g., 330 kPa corresponds to 3.5 bar) and must not be exceeded. The reason for this specification is to limit or restrict compromises made to comfort (e.g., road and tire noise, particularly when the vehicle is traveling over pavement joints), traction (e.g., during braking), wear, and fuel consumption. Those who place high value on low fuel consumption can considerably increase their tire pressures without having to be concerned any further."