What you need to know about car tire ply and ply ratings

A tire is defined according to several criteria which are presented in the form of numbers and letters. This may sound a bit abstract, and yet, it is very simple! In order to clarify this point, let's take an example with the dimension 225/45 R17 91W.

Read tire size

225 = width

45 = height

R = radial structure

17 = diameter

91 = load index

W = speed index

Now you know how to read a tire.

Meaning of tire characteristics

Alright, let's dig a little deeper. To begin with, the width of the tire is expressed in millimeters. As for the height, it is expressed as a percentage and corresponds to the ratio between the height of the sidewall and the section width.

The diameter corresponds to the height of the rim and is noted in inches (1 inch = 2.54 cm). Our tire is therefore 43.18 cm in diameter.

In our example, “91” corresponds to the load index. Attention, this number is not equivalent to the kilos that the tire can support, it is just an indicator. This figure is equivalent to a set number of kilograms. With a weight index of 91, the tire can support up to 615 kg. (See the load indices table)

And what is R? The R stands for "radial". This is the structure most often used in pneumatics. Before its invention, manufacturers used the diagonal structure (noted D), less efficient for various reasons (faster wear, less economical, lack of grip). If the tire is "belted", the corresponding marking is a "B".

Finally, the maximum speed that the tire can withstand is indicated by a letter. In our case, the “W” refers to a speed index. To know it, you have to look at the equivalences. (See our speed index table). The tire we have chosen to analyze can travel up to 270 km/h. For some “high performance” models, it is possible to read “ZR” or “ZR(Y)”, which means that it can exceed 240 km/h and 300 km/h.

Of course, to this is added the name of the manufacturer and that of the model. The sizes we have chosen to illustrate the article correspond to the Continental Sportcontact 3 model or the Dunlop SP Sport 01 A.

What you need to know about car tire ply and ply ratings

A tire is defined according to several criteria which are presented in the form of numbers and letters. This may sound a bit abstract, and yet, it is very simple! In order to clarify this point, let's take an example with the dimension 225/45 R17 91W.

Read tire size

225 = width

45 = height

R = radial structure

17 = diameter

91 = load index

W = speed index

Now you know how to read a tire.

Meaning of tire characteristics

Alright, let's dig a little deeper. To begin with, the width of the tire is expressed in millimeters. As for the height, it is expressed as a percentage and corresponds to the ratio between the height of the sidewall and the section width.

The diameter corresponds to the height of the rim and is noted in inches (1 inch = 2.54 cm). Our tire is therefore 43.18 cm in diameter.

In our example, “91” corresponds to the load index. Attention, this number is not equivalent to the kilos that the tire can support, it is just an indicator. This figure is equivalent to a set number of kilograms. With a weight index of 91, the tire can support up to 615 kg. (See the load indices table)

And what is R? The R stands for "radial". This is the structure most often used in pneumatics. Before its invention, manufacturers used the diagonal structure (noted D), less efficient for various reasons (faster wear, less economical, lack of grip). If the tire is "belted", the corresponding marking is a "B".

Finally, the maximum speed that the tire can withstand is indicated by a letter. In our case, the “W” refers to a speed index. To know it, you have to look at the equivalences. (See our speed index table). The tire we have chosen to analyze can travel up to 270 km/h. For some “high performance” models, it is possible to read “ZR” or “ZR(Y)”, which means that it can exceed 240 km/h and 300 km/h.

Of course, to this is added the name of the manufacturer and that of the model. The sizes we have chosen to illustrate the article correspond to the Continental Sportcontact 3 model or the Dunlop SP Sport 01 A.

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