that last post was correct. what people dont realize is that even tho the tire size changes, ie from an 18 to a 22, the psi remains the same in MOST CASES. you cant think of a psi as a normal numerical value like a size. its pounds PER square inch. so even if you increase the square inches on the tire, the pound pressure per square remains the same. for example, if i had said 18 and 22 tires next to each other, completely falt and started filling them at the same time, the 22 would take longer to fill because it has more void, but you would still end up with (for example) 40 pounds at the end for each. the 22 would take longer to fill, but the punds per suare inch would be the same. this does not apply to xl or lt capacity tires, as this changes, and some vehicles have special fitment notes saying a size is approved if a higher psi is used, thus increasing its load capacity. those are acceptions