Dating the age of tires
The more plies, the higher the load the tire can take.
Also indicated are the materials used in the tire; steel, nylon, polyester, etc.
Tire Identification Number – The letters DOT preceding the number indicate that the tire meets all Federal standards as regulated by the Department of Transportation.
The first two numbers or letters after the DOT indicate the plant where the tire was manufactured.
Diameter – This number indicates the inside diameter of the tire in inches, which is also the outside diameter of the rim.
Oils and chemicals in the rubber compound start to evaporate or break down because of UV exposure.The proper inflation will be found on a plaque, usually inside the driver's doorjamb.Inflation is measured in PSI (Pounds per square inch) and should always be measured when the tire is cold.If the number begins with a "P" the tire is called "P-Metric" and is built in the US. The only difference between the two is a very slight one in terms of how load rating are calculated for the size, but the two are essentially interchangeable.Aspect Ratio – The aspect ratio designates the height of the tire, measured from the top edge of the rim to the top of the tire, as a percentage of the width.
What this means is that the upper sidewall of the rim in this picture has a height of 65% of the 225 millimeter width, or 146.25 millimeters.