First, while all tires have a pressure designation number (psi means pressure per square inch) on each tire, do not use that number as your guide. Instead, you will find it on the driver's door which is visible when you open the door. It's this information that is provided by your vehicle's manufacturer (not the tire manufacturer) that matters.
When tires are not set to the right pressure, several things can be impacted. First, is the safety issue. No one wants to experience a tire blow-out when you're driving 65 miles an hour on the highway. Second, improperly inflated tires (with too little or too much air) can lower your gas mileage. And third, it will result in uneven tread wear and diminish the expected life of the tires.
But there's more to tires than just air. Having your tires regularly rotated and balanced is what keeps them wearing evenly. Whenever you bring in your vehicle for an oil change, that's the time to have your tires inspected and rotated.
The final issue to be concerned with when it comes to your tires is their alignment. The simple explanation is that they should be straight up and down. You generally can't tell that by just looking at them though. What you would notice is that while the steering wheel is straight when you're driving down the road, the car "drifts" to the left or to the right seemingly on its own. That's when an alignment should be performed.
So get into the regular habit of measuring your tire pressure on all 4 tires (and don't forget to check your spare tire as well). Once a month is a good rule of thumb. If they need air, add it - don't delay. It's not worth it to take chances with your tires when it comes to your safety or your pocketbook.
No matter what the issue is, we are there to help.
Until next month, happy travels!