08/02/2022
๐ Today's GOOD TO KNOW car tips:
What do the numbers on tyres mean?
On each tyre, you will usually find a series of numbers and letters that look something like this: 205/55R/16/91V
Each of these digits/letters represents something different and provides important information. When it comes to how to read tyre size, the first five digits of the code are the ones to concentrate on.
The first three digits belong together and indicate the width of the tyre (in millimetres). In the example above, the tyre is 205mm wide.
The two digits following the first slash are what is known as the aspect ratio. Essentially this is the height of the tyre as a percentage of the width. So, in the example, the tyre has an aspect ratio of 55, meaning the profile height is 55% of its total width (112.75mm).
After the number that indicates the aspect ratio, there is a letter. In the example used, this is R. This stands for Radial and is a specific type of construction. It means that the steel belt inner construction is angled at 90 degrees to the direction of travel, resulting in extra strength. Almost all new car tyres are radials.
The next two digit number after the slash indicates the diameter of the wheel (in inches) - essentially how wide the wheel is across the centre. It is measured as the distance between the two bead seat areas. In the example, the number is 16 so will fit a 16-inch wheel rim.
The next two digits belong together and represent the Load Index. This is the maximum load that the tyre is able to carry when inflated to the correct level. Each double digit number represents a different weight (in KGs). 91 is the number in the example and this corresponds to a weight of 615KG. Overloading any vehicle is dangerous and can increase fuel consumption, impact on handling, and can even occasionally cause catastrophic tyre failure.
The final letter represents the Speed Rating of the tyre. This is the maximum speed that the tyre can cope with under its maximum load. Each letter represents a corresponding speed. The example we are using has an V rating which equates to 149mph (240kmh).