Automotive manufacturer's have ratings for the "recommended pressure" they think you should use in the tires on your vehicle. These ratings can be found either on the door/pillar placard on the driver side of your vehicle or in the owners manual. these pressures are determined by the engineers who designed the VEHICLE, NOT the engineers who designed the tires! The tires also have a recommended MAXIMUM pressure rating. Usually, for passenger vehicles, if you desire better fuel milage, longer tread/tire life, optimal handling/safety, and maximum comfort(WHO DOESN'T DESIRE ALL OF THESE THINGS?!?) then the pressure you are looking to KEEP(KEEP A CLOSE WATCH ON THE PRESSURE IN YOUR TIRES AT ALL TIMES! CHECKING WHEN YOU ARE REFUELING, EVERY TIME, IS A GREAT HABBIT TO DEVELOP!)(BTB...CHECK YOUR OIL WHILE YOU ARE AT IT!) is in between the auto man. and the tire man.'s ratings. a quick translation, if tire says (44 psi max.) 38 is PROBABLY best! If it says 35 psi max, 32-33 psi is probably enough and best! If the tire says 51 PSI max. then 40 is probably good but it couldn't hurt to try 45, see how it feels, see how it wears. I will update this review dramatically, frequently, very soon in the future. Please Vote! and Please Check back! Thank's and i hope this helps you! Please Check Out my other Guides! And Please feel free to contact me and ask questions!