Features

The numbers on the tire correspond to the tire type, cross-section, sidewall height to cross-section width, construction of the tire, diameter, maximum load capacity and speed rating.

Function

The first three numbers refer to the width of the cross-section in millimeters and the next two numbers represent the ratio of sidewall height to cross-section width. After the letter, the next two numbers represent the diameter of the wheel, measured in inches.

Significance

You should get a tire that has the same specifications as the car manufacturer recommends. You can find this information on the car, either on the fuel-filler door or placard in the doorjamb or glove compartment, or by consulting your owner's manual.

Considerations

You should also consider the speed rating, tread-wear rating and seasonal characteristics of tires when determining which tire to purchase. For example, if you live in New England, you should consider special winter tires.

Time Frame

The tire specs also give the age of the tire. Find the letters "DOT" and the next two numbers represent the week it was made and the final two numbers represent the year the tire was made. Consumer reports advises against buying tires that are more than a couple years old.

Source:

Consumer Reports Tires

Michelin Tire Buying Guide

Tire Guide from Consumer Reports