Tyre size explained

If you've ever looked at the side of your tyres, you may have noticed there are subtle codes and labels. These markings display key information such as your tyre size and performance. A typical tyre marking will look something like this: 205/55 R16 91V.

If the letters and numbers seem confusing, don't worry. We've broken down exactly what each part means to help you read your tyre more easily:

Tyre width

The first component of the tyre code explains the nominal width of your tyre in millimetres. The example tyre measures 205mm, from sidewall to sidewall.

Tyre height

The next number, '55' demonstrates the aspect ratio of the tyre. This means that the height of the tyre's sidewall is measured from the rim to be 55% of the tyre's width. In this case, the sidewall height measures 112.75 mm (0.55 x 205mm).

Tyre type

The letter 'R' that follows demonstrates the tyre's construction type, meaning 'radial'. Almost all tyres on the roads nowadays are radial.

Other types include; 'ZR', meaning the tyre has been adapted to perform at speeds above 149mph. Also, 'B' refers to a Bias-ply tyre, while 'D' means diagonal construction.

Rim diameter

The number attached to the letter 'R' tells you the size of the wheel or rim diameter. This tyre will fit over a rim that is 16 inches.

Load index

The last set of numbers refers to the load index or the maximum weight that the tyre can carry when properly inflated. In this case, the tyre would be capable of holding a maximum of 615kg.

Speed rating

Finally, the last letter indicates the maximum speed that the tyre is certified to carry its load safely. Different letters represent different speed ratings for the tyre, with 'V' capable of handling such speed without fail. The letter 'V' indicates a maximum speed of 149mph or 240km/h is possible.

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How to read my tyres

Check the sidewall of your tyre for a sequence like 205/55 R16 91V. Make sure to read these details carefully for accurate information. If the markings on your tyre's sidewall are worn off or hard to read try these steps:

1. The correct tyre specifications are usually listed in your vehicle's user manual.
2. Look for a sticker on the inside of the driver's door frame or the fuel cap cover; it often contains tyre size and pressure information.
3. Take it to a specialist at your local garage. They can inspect your vehicle and recommend the correct size and rating.

When it comes to determining your tyre sizes, one of the most efficient ways is to check the code found on your tyre sidewall. The details on breaking this code down can be found in the information above.

However, you can also determine your tyre size using your car's registration number. Figuring out your tyre size by reg is simple with our handy tyre finder. Just enter your reg number and a list of compatible tyres will be displayed.

Alternatively, your vehicle's manufacturer should have provided you with your tyre's details in your owner's manual.

How to make sure I buy the right tyres

Now you know how to read your tyre sidewall, it's time to choose the best tyres for your vehicle.

When you purchase your tyres, ensure that you have selected the correct rim size and ensure width compatibility between the tyre and rim. You can also consider the type of driving you're doing as certain car makes, drivers, and climates can often benefit from winter or all-season tyres. 

Tyre sizes

If you're unable to find your correct tyre size here, please refer to our tyre finder by entering either your reg number or known tyre size at the top of the page.

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