When it is time to get new tires and a car mechanic in Phoenix asks you what size your tires are, you may have no idea how to retrieve this information. You have probably seen the series of numbers and letters on your tire’s sidewall before, but didn’t know what any of it meant. Sometimes referred to as a tire code, this alphanumeric combination can actually tell you everything you need to know about your tires, and this guide will help you make sense of what those tire specifications mean:
- Tire width: The first number in a tire code represents the nominal section width of the tire, and is a three-digit number that is measured in millimeters. This measurement is from one outermost edge of the tire to the other, and encompasses the total maximum width. If you want to know what this number is in inches, simply divide the width in millimeters by 25.4, which is the number of millimeters per inch. For example, if your tire width is 225mm, dividing 25.4 by this number means that the tire is 8.86 inches wide.
- Size and construction: The second set of numbers in a tire code is the tire’s sidewall aspect ratio. This two-digit number is a percentage value that represents the height of the tire, and is calculated based on its relationship to the width of the tire. The larger this number is, the more sidewall there will be. Using the tire with a width of 225mm from earlier, a tire code that reads 225/60 means that the numerical value of the sidewall height will be 60 percent of the tire’s width. We already know the width of this particular tire is 8.86 inches, so the amount of sidewall from the rim to the tread on the outermost portion of the tire is 5.316 inches. This width and height ratio is always accompanied by a letter that describes the internal construction of the tire, which is most commonly an R. The R means that the tire’s internal components are layered radially, extending outward from the center of the tire. Some other well-known tire constructions are D and B, which indicate either diagonal or belted orientations, respectively.
- Load carrying capacity: Also commonly referred to as the tire load index, the load carrying capacity refers to the amount of total weight that an individual tire can firmly support, and is the last set of numbers in a tire code. A tire on a standard four- to five-passenger vehicle has an average index of 75-100, which translates to between 852 lbs and 1,764 lbs. The load capacity of each tire is then multiplied by four to determine the full load that your car is able to safely carry. It is important to note that this number is assigned to a fully inflated and operational tire, so if the tire is in any way compromised, the ability to carry a full load will be affected.
Different manufacturers use differing versions of tire codes, but the specifications and their meanings are universal. If you need help from a car mechanic in Phoenix with a faulty tire, or want to determine which tires are best for your car, the staff at S & J Auto Repair & Rental is ready to help get you back on the road right away.