Then can anyone explain the increase in gas mileage from upping th PSI to 44?
Yes, more PSI in a tire gives it the capability to support more. But correct tire pressure is a factor of vehicle weight, tire construction, and size. Tires with stiffer sidewalls require LESS pressure to support the same load as a tire with a softer sidewall. The idea is to have a tire that uses the air pressure AND sidewall to evenly support the tread giving it an even wear pattern.
For example: A soft sided Space-Saver-Spare tire may require 50psi to support 1200lbs even across the tread. A standard road tire would require less since the sidewalls are tougher. The amount less would be determined by the sidewalls strength, the treads rubber compound and how wide the tread is. The wider the tread, the higher the pressure needs to be to support the center.
I started this thread, not to argue about what the proper inflation should be, but instead to see if anyone had any prior experience with a good pressure on this size tire and vehicle weight combo. I have a fairly good experience with motorcycle tires and how they should be inflated for racing applications. The proper inflation is NOT determined by what's on the door of a car unless you keep using the same brand and size of tire. If you switch tires you're switching to a design that the manufacturer never ran any calculations for and the psi rating may not apply anymore.
In the past we (my bike racing team) have always started a new tire with a simple formula and using the vehicle's weight and info printed right on the tire.
You take the GVWR and divide it by the number of tires. Then you dived that by the maximum load rating of the tire at it's maximum pressure. This gives you a percentage which you then multiply by the maximum pressure stated on the tire.
Generally this gives you a minimum pressure to use as a starting point; the final psi is somwhere close and usually a tad higher. HOWEVER, in my case with these Pirellis I noticed a decrease in performance and I wanted to see if anyone had a better pressure to run. FYI, using that method, the
Pirelli tires would be inflated to 30.2 psi.