A lot can be learned by reading the tire's sidewall. The following illustrations show typical information on the sidewall of passenger car ang light truck tires.Being able to read and understand the information molded on a tire's sidewall will make it easier for you to know what tire you need.
There are a number of different systems in use today that describe the various tire sizes used on performance, passenger and light truck vehicles. An attempt is currently underway to develop a worldwide system, but presently you must be familiar with several different systems.
PASSENGER CAR TIRE SIZING SYSTEM
NUMERIC SIZING SYSTEM.
The first system developed for tire sizing was used until the late 1960s, but provided only the cross section width of the tire and the rim diameter in inches. If the section width ended in zero (e.g., 7.00-14 or 7.50-14), the tire has a common aspect ratio of about 92. For section widths not ending in zero (e.g., 8.25-15), the tire was considered "low profile" with an aspect ratio of about 82.
ALPHA-NUMERIC SIZING SYSTEM.
In 1968, a new concept was introduced worldwide. The Alpha-Numeric Sizing System is a load-based system where tires are designed by their load-carrying capacity and aspect ratio. The first letter is the load and size relationship, with letter, the smaller the size and, of course, the lower the load-carrying capacity of the tire.
METRIC SIZING SYSTEM.
Because Europe primarily uses the metric system of measurement, the Metric Sizing System was developed. It is essentially a conversion of the Numeric Sizing System. Section widths are notated in millimeters instead of inches. Originally, tires not identified with an aspect ratio were assumed to be 82-series. When 60- and 70-series tires appeared, the aspect ratio was added to the nomenclature, similar to the P-Metric System.
ISO METRIC SIZING SYSTEM.
The International Standard Organization (ISO) Metric System combines the Metric System with a service description provides the load index along with the speed-rating symbol.
MILLIMETRIC SIZING SYSTEM
The Millimetric Sizing System is similar to the Metric Sizing System except that the rim diameter is also represented in millimeters. These rim diameters are unique in size and can only be used in combination with each other.
LIGHT TRUCK TIRE SIZING SYSTEMS
LIGHT TRUCK NUMERIC SYSTEM
Similar to the Numeric Sizing System for cars, it lists the section width in inches, construction type, rim diameter in inches, plus the light truck designation
LIGHT TRUCK METRIC SYSTEM
Similar to the P-Metric System, except the P is replaced with the LT (Light Truck) designation. Also, LT-Metric and P-Metric tires differ in construction.
LIGHT TRUCK HIGH FLOTATION SYSTEM
The same as the Light Truck Numeric System with tire diameter added to the front.
Load Index
Many tires come with a service description added on to the end of the tire's size. These service descriptions contain a two-digit number (load index) and a letter (speed rating). The load index is a representation of the maximum load each tire is designed to support. Because the maximum tire load-carrying capacity is branded on the tire's sidewall, the load index is used as a quick reference.
Speed Rating
In Germany some highways do not have speed limits and high speed driving is permitted. Speed ratings were established to match the speed capability of tires with the top speed capability of the vehicles to which they are applied. Speed ratings are established in kilometers per hour and subsequently converted to miles per hour (which explains why speed ratings appear established at "unusual" mile per hour increments). Despite the tire manufacturer's ability to manufacturer tires capable of high speeds, none of them recommend the use of their products in excess of legal speed limits. The maximum operating speed of a vehicle must be limited to the lowest speed rated tire on the vehicle.
Balanced tires provide a smooth ride and help protect your tire from uneven tread wear. As new vehicles become lighter it's becoming increasingly important to keep your tires balanced. Heavier cars helped smooth out the ride and mask vibrations. You should let an expert mount and balance your tires, but you can do the job yourself if you have the expertise.
Moderately Challenging
Instructions
Things You'll Need
Here at AmericanTireStores.com we would like to help you, the consumer in any way possible to get the most out of your tires and this is a step by step process on how to repair your flat tire if this problem ever arises.
This article on Basic Tire Puncture Repair is the first in a four-part series on basic services performed in tire stores. This first installment breaks down each repair step with photographs and descriptive captions and should be helpful to not only newly trained technicians, but also veterans who want to brush up on their techniques. The information is a compilation of accepted industry procedures and standards from the Rubber Manufacturers Association and the Tire Industry Association; the photos were supplied by Myers Tire Supply/Patch Rubber Co., a supplier of repair materials and tools.
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