Car tyre sizes guide
There are several scenarios in which you will need to change your tyres. Perhaps you have a puncture - or your tyres are running close to the minimum legal tyre tread depth. Alternatively, you may want to replace your tyres to sell your car.
Whatever the reason, it’s helpful to know your car’s tyre size. This will help you avoid any unnecessary hassle when it comes to replacing tyres.
In this guide, we will explain how to identify tyre sizes for any vehicle – and how to interpret the numbered markings found on tyres.
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How do I find my car’s tyre size?
The key to finding your tyre size is understanding the numbered imprints on your tyres. Your tyre size (a sequence of numbers and letters) can be found on the sidewall of your tyre. This sequence indicates the following attributes:
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Tyre width
The width of your tyre is indicated by the first three digits in the sequence. This three-digit number reflects the width of the tyre in millimetres.
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Tyre height
The next two digits reflect the height/profile ratio (represented as a percentage of the tyre’s width). This number denotes the tyre’s section width divided by its section height.
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Tyre type
The first letter in the sequence indicates your tyre type. One of the following letters will be used here:
- ‘B’ (bias-ply).
- ‘D’ (diagonal construction).
- ‘R’ (radial).
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Rim diameter
The next two numbers in the sequence reflect the size of the wheel rim diameter in inches.
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Load index
The next two numbers indicate the load index. The load index is the maximum load (in kilograms) that the tyre can support when it is properly inflated.
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Tyre speed rating
The sequence ends with another letter, which represents the tyre’s speed rating. These tyre ratings are used to indicate the maximum speed at which your vehicle can be driven.
Tyre speed rating Corresponding speed (mph) S 112 T 118 U 125 H 130 V 149 W(ZR) 168 Y(ZR) 186 ZR Above 149
Understanding the numbers on a tyre
Let’s look at an example using the tyre size 205/55 R16 91V (a reasonably common size):
- The first three digits indicate that the tyre is 205mm wide – and the tyre height is 55% of the width.
- The tyre type is ‘R’, meaning it is a radial tyre.
- The rim diameter is 16 inches.
- Its maximum load is 91kg.
- Finally, its speed rating is ‘V’, meaning the maximum speed at which the vehicle can be driven is 149mph.
Once you’ve familiarised yourself with these numbers and their meanings, understanding tyre sizes becomes simple.
Can you check tyre size by registration?
Yes, a quick online search will reveal a selection of tools that allow you to check tyre sizes by registration.
Whilst these tools are usually accurate, there is always the possibility that your chosen tool will recommend an incorrect tyre size. Therefore, we advise checking the code imprinted on the tyre you want to replace. This will ensure you purchase the correct tyre(s) for your car.