How To Read Your Tyre Sidewall Markings - A Guide for Car Owners

Every car owner has had the chance to take a good look at their tyres at least once—maybe you were trying to spot a puncture, maybe you were picking out new ones, or maybe you just had time to kill. In any case, you’ve probably spotted a bunch of letters, numbers, and symbols on your tyre’s sidewall. These are nothing more than your tyre’s specifications, the knowledge of which can come in handy when you’re looking to make decisions about tyre replacement, maintenance, and compatibility.

Let this article serve as the comprehensive guide you need to understand tyre sidewall markings.

Every character on the sidewall of a tyre corresponds to specific details about the tyre’s size, construction, performance capabilities, and more. While it isn’t as daunting as it seems, it can take some looking into to make sense of it completely.

Let’s explore these markings step by step:

The first set of characters is a three-digit number that represents the tyre width in millimetres, from sidewall to sidewall. Which, in the case of the image below, is 245mm.

The tyre width is then followed by a slash (/) that then features a two-digit number; this is your tyre’s aspect ratio. The aspect ratio represents the tyre’s sidewall height as a percentage of its width. As is shown in the picture, this tyre’s aspect ratio is 45% of its width.


The letter that comes after signifies its construction type. Here, the letter ‘R’ shows us that this tyre is of radial construction, which is the most commonly used and manufactured tyre today. Other types are ‘B’ for bias belt and ‘D’ for diagonal.

You will then find another two-digit number that represents the diameter of the wheel rim in inches. This measurement helps ensure your tyre fits the rim correctly.

While the first set of numbers helps us make sense of information related to the tyre’s size, the combination of numbers and letters after indicates the tyre’s load-carry capacity and speed rating. The load index represents the maximum weight that can be supported by the tyre, and the speed rating indicates the tyre’s maximum safe speed.

But have you considered why it's so important for you to know how to read tyre markings? Knowing how to read tyre sidewalls can be quite beneficial for many reasons, especially if you're a vehicle owner. From helping you choose the right tyres to ensuring you buy the right ones, the information on tyre sidewalls can help you make these decisions!