Why Do Tire Widths End in ODs?

The ETRTO, established in 1964, is responsible for setting tire size standards for the European market. A key regulation by the ETRTO is that tires for passenger cars, light trucks, and commercial vehicles must have a width ending in a 5 to differentiate them from motorcycle and agricultural vehicle tires.

This is important for standardization in the tire industry. Having car tire widths end in 5 makes it easier for manufacturers, distributors, and consumers to identify, produce, and choose the right tires for their vehicles.

It ensures consistency in production and that products meet certain safety and performance standards. Standardization also simplifies tire design and installation, ensuring a proper fit and optimal performance for vehicles manufactured to these standards.

*As illustrated below, car tire widths always end in 5.*

Typically, tire size specifications are printed on the tire sidewall, for example, 205/45R17 or 225/60R16. Here, the first number, 205 or 225, indicates the tire width in mm, ranging from 155-315mm depending on the vehicle type.

The next two numbers after the slash denote the tire’s aspect ratio, which is the percentage of the tire’s sidewall height to its width, typically between 55-75% for most passenger cars.

The letter ‘R’ indicates the radial construction of the tire, an industry standard for passenger cars, and the most common type of tire. Other types may be denoted by B, D, or E.

Finally, the last number in the sequence, such as 17 or 16, represents the wheel diameter in inches that the tire is designed to fit.

These are the basic parameters that car owners need to consider when choosing tires that match the size specifications provided by the vehicle manufacturer.

*Source: VTC news*