Quote from: derfdog15 on January 09, 2017, 01:16:50 PM
Good find, may I ask why you needed this info?
Because I'm way too analytical. LOL. You might be sorry you asked, but here you go
:
I was just curious if Ford recommended a higher pressure for PI vehicles to increase overall carcass stiffness for a more performance oriented application (where ride comfort might not be as big of a concern as it is on civilian models).
I believe, though, that the PI SUV recommended tire pressure (36/36) is higher due to the lower internal volume of the PI recommended tire (245/55R18).
I did a very simplistic volume calculation of the Sport tires (255/50R20) vs PI tires (245/55R18), and my simple calculator says you'd need to run 36.8 PSI in the PI tires to have the same number of air molecules as my Sport. My calculator, though, is very basic and does not take into account any differences in the well design/volume of the wheel itself, which probably accounts for the difference I'm seeing between my 20" OE wheels and the 18" PI wheels.
Using the same calculator, my winter Blizzak tires (235/65R18) have a slight increase in volume over my Sport tires, and in theory, I could run approximately 31.7-32.5 PSI in the Blizzaks and have the same number of air molecules as my OE 20" tires. I'll just stick with my factory 35 PSI, since that's where the alignment was done on the winter setup.
The calculator would probably work decently well for different tire sizes on an identical rim.
