The abbreviations used in car manufacturing can seem like gibberish to the uninitiated. Weird numbers like "P195/75R14 92S" can make consumers throw up their hands in despair and turn over responsibility for choosing new tires to the salesperson at the dealership or to a knowledgeable family member. In reality, these numbers are easy to decipher, once you understand the following key. The first part of the sequence identifies the type of vehicle the tire is intended for. P is a passenger tire , T is for temporary use (as a spare tire), and LT is for light truck. The first numbers, before the slash, indicate the section width of the tire. This is not the tread width, but the width of the widest point of the tire. This number is in millimeters and the smaller the number is, the shorter or narrower the tire will be. Immediately following the slash is the aspect ratio. It is the height of the tire expressed as a percentage of the section width. Higher performance tires have a smaller aspect ratio. The next letter describe the construction or type of the tire. Standard car tires will have an R for radial ply construction. Next is the rim diameter. Unlike the previous measurements, rims are measured in inches. The last sequence is sometimes referred to as the service description. It consists of a number indicating the load index and a letter designating the speed rating. A load index of 92 means that the tire can carry a load of 1400 pounds. You'll want to refer to a maximum load-carrying capacity chart to determine what the index means. The speed rating tells you what speed the tire can safely sustain. S indicates speeds up to 112 mph, H is good for 130 mph, V for 150 mph, and Z for speeds over 150 mph.