If you would like to know what type of tyre you are using in your car you just have to look at the information displayed on one of its sides.
There are two codes. First you can see the name of the brand and after a series of numbers and letters which indicate the dimensions and features of the tyre such as height, width, structure, diameter, load index and speed rating.
Let’s have a look at each code individually:
- 245: This is the width of the tyre in millilitres. In standard sizes this number varies between 125 and 335 millilitres.
- 40: This number is expressed as a percentage and it indicates the aspect ratio of the tire, in other words, the relationship between the height and width. In our example, the sidewall height is 40% of the tread width. The lower this percentage, the lower the sidewall height and the better the grip when cornering.
- R: This letter makes reference to the structure or construction of the tyre. Nowadays virtually all tyres are “radial” and so this information is often omitted. The tyre being “radial” means that the plies of tyre cord extend across the casing from bead (also called “heel”) to bead.
- 18: This indicates the inside diameter of the tyre or rim height in inches. Usually this varies between 10 and 23 inches. In our example the tyre has a diameter of 18 inches.
- 93: This is the load index and it indicates the maximum load the tyre can carry when it is inflated to its maximum safe pressure. In order to know what this means in kilos you have to check the corresponding look up table:
In our case, with an index of 93, the maximum load that the tyre can handle is 650 kg.
- W: This last letter establishes the speed rating and it indicates the maximum speed that a tyre can carry a load safely. You could always equip your vehicle with a higher specification tyre than is recommended but never with an inferior one. The equivalent recommended speed indexes are:
Taking all this into account, while always following the advice from a trusted provider, you will be more prepared to confidently choose the best tyres for your car.