For many of us our vehicles are an essential part of every day life. We use them to get to work, take the kids to their activities, and run errands all over the place. Our lives would be a lot different without cars. But as essential as our vehicles are in our lives we often neglect, or take for granted, one of the vehicles most important elements...the tires. Tires are a key element in our vehicles functionality. They help to give us a smooth and comfortable ride, provide traction to keep us on the road and allow us to stop in a timely manner, and when properly inflated can improve your gas mileage . This is why it is so important to not only maintain your tires but also to ensure that you have the correct size. The wrong size tire, depending on the degree of difference, can cause your alignment to shift, interfere with your odometer and speedometer, as well as affect the car's handling. Before you buy a new set of tires it's important to know what size tires your vehicle uses, even if you are planning on going through a tire dealership. You can find this information by looking at your tires, it should be printed on your vehicles sidewall, or in your owner's manual. If neither of these locations can give you the information you need you can always contact the dealership to find out the correct tire size . When it comes to sizing a tire there are 7 main elements: service type, section width, sidewall aspect ratio, internal construction, speed rating, tire and wheel diameter, and service description. All of these elements play an important role in determining the size of a tire; however when purchasing tires from a dealer the most important elements to know are the section width, the sidewall aspect ratio and the tire and wheel diameter. The section width is the first 3-digit set of numbers and it is found by measuring the widest point of the outer sidewall to the widest point of the inner sidewall in millimeters. This is important to know so that your new tires will fit properly on your vehicle and your wheels without sticking out too far. The second 2-digit number is the sidewall aspect ratio. This number measures the ratio of the tires sidewall height, rim to tread, to the section width. So 50 would mean it is 50% of the section width. Again knowing this number is important so that you tire fits properly within the wheel well and on your vehicle. Finally the last 2 digits in your tire size indicate the tire and wheel diameter. This is an important number because it measures the diameter of both the tires and wheels. If this number is too big or too small, compared to your wheels, you may have issues with getting them on, especially if you have custom intro wheels . Your best bet is to make sure that the numbers match up.