Lowered my rear windows and thought I had a helicopter flying overhead. Turns out to be tires that do not wear evenly. The dealer says it is tire pressure. The dealer recommends 32psi. From what I read in your comments 42psi on front and 40psi on rear. My tires need replacing. Have good tread on middle of tire but wear terribly on the inside. My current mileage is 25,800 miles. I am going to keep my rear windows up and get a little more mileage. My question is about tire pressure changing when traveling. As the tires heat up I am sure the air expands. And what happens when one travels in the colder climates. Does air pressure decline in the colder climates. A smaller tire then is prone to uneven pressure depending on the driving conditions. Will this cause tires to wear unvenly? Or is it the allignment on the Prius that gets out of wack easily? Rotate the tires and the out of wack front kills the tires. And what happens if you use a gas vs air pressure. Will that gas be affected by heat and cold like all gasses? Changing the tire type to a Michelin Hydro edge or a Michelin Harmony - Will that increase the tire life? I am going to drive another 5,000 miles and listen to what you have to say. Want a tire that is safe. Gives good road handling and decent mileage. Please keep sharing your thoughts.