Do you find yourself smiling and shrugging helplessly when tyre salesmen reel off lines of numbers and letters to you? Have you ever been persuaded to ‘upgrade’ to a more expensive set of tyres than you had originally chosen only to find that they do not properly fit your make and model of car? Or do you simply leave it all up to your mechanic, hoping that they will understand all those mysterious codes and give you the best set of tyres for the best possible price?
If you have answered yes to any of these questions, you are not alone, but understanding tyre codes is not as hard as it can seem. Let us take a look at what all those numbers and letters actually mean.
What Tyre Codes Look Like
A typical tyre code looks like this:
Three numbers then a forward slash and two more numbers. There is a small space, then a letter. Next, there is a 2 digit number. Then will come two or three digits, usually between 75 and 105. A single letter follows that. Next follow a grouping of four or five letter codes, and finally a sequence that most people will recognise: a number out of 52 followed by a two-digit number. Let’s see what these all mean.
Tyre Width and Aspect Ratio
The three digits offers the width of your tyre in millimetres: so a twenty-centimetre tyre would be: 200.
The two digits are the percentage of the width that comprises the sidewall height. For our example, it is 50. As fifty percent of 200mm is 100mm, we know that our sidewall height is 10cm.
The first single letter refers to the construction of the tyres: R for radial, B for Bias-ply and D for diagonal construction. Our example tyres are radials.
The two-digit number after the construction letter is possibly one statistic that most people will easily understand: it is the total height of your tyre from ground to top of the tyre, and it can be anywhere from fifteen inches to about twenty-two. For our example, we will use 18 inches.
Load Index and Speed Rating
The load index and speed rating are among the more complex numbers, but the beauty of it is that you just need to know your vehicle’s maximum load index and speed rating and ensure you buy the appropriate tyres. For example, a car with a load index of 84, should not carry more than 500kg which is the maximum permitted weight. A car with a top speed of 210km/h has a speed rating of H. Most tyre manufacturers make it easy to choose the right statistics for your vehicle, then sorting out a list of recommended tyres for you. And all this information will be in your car’s instruction manual or readily available online.
Other series of letters and number might follow, depending on if the tyres are run-flat tyres (SSR), if it is suitable for use in mud and snow (M+S), and if it is compliant for use in the USA, for American users (DOT – which stands for Department of Transport).
Finally, you will get the week and year of manufacture, such as the sixteenth week of 2016, which would look like this: 16/16.
Our mythical tyre then has the following code: 200/50 R 18 84 H SSR M+S DOT 16/16. We now know that this means that it has 20cm wide tyres, with 10cm high sidewalls, that they are radials, 18 inches in diameter, that the car has a top carrying weight of 500kg and a top speed of 210km, that they are run-flat safe, suitable in poor wintry weather, and that they were made at around the end of April in 2016.
Now see if you can make out the code on your old tyres when you next purchase some new tyres in Basingstoke! You can try and shop fuel efficient tyres in Basingstoke at Headley Tyres and see how much you can save by using tyres with a better rating!