The Complete Guide to Every Tyre Sidewall Marking

Look around the side of your vehicle’s tyres and you’ll find many numbers, letters and words, some of which are easy to understand and others completely unknowable. These sidewall markings are important information if you’re looking to replace a wheel or tyre, as you’ll need to make sure your current tyres will fit new wheels, or new tyres will fit your current wheels.

Understanding these markings is crucial to ensure that you choose the right tyre for your vehicle and driving needs, which is why we’ve made a comprehensive guide to each of them. Going clockwise around the wheel starting from the brand name, we explain what each one means in detail.

Tyre Markings Explained

Brand Name

The most recognisable marking on your tyre will be its brand name. Hopefully, you’ll know what name you’re looking for and it’s one of the largest texts on the tyre overall. This is the most self-explanatory of all the markings, as the tyre makers want to proudly display its name across the rubber.

European ECE Tyre Approval

The Economic Commission for Europe (ECE) creates the safety standards for all European-made tyres, amongst other things. Their marking should be on every tyre you use, and has the letter ‘E’ followed by a number that indicates the country the tyre was tested in - which will most likely be the UK, which is ‘11’. Find ‘E11’ enclosed in a circle on your new tyre, and it lets you know that the tyre has been approved as safe to use.

Manufacturing Date Code

If you’re buying a new set of tyres, you won’t have to worry about them being too old to be safe, but the manufacturing date lets you know when it was created. You can find it amongst a long set of letters and numbers that begin with ‘DOT’. The manufacturing date is at the end of the number and is split into 4 numbers. The first pair of digits which shows the week of the year it was manufactured, and the second pair which gives the year. 

Country of Origin

The chances are that UK drivers will have tyres that say ‘UNITED KINGDOM’ on the side. Every tyre has a marking telling you clearly where the tyre came from, so if you’ve imported a vehicle from overseas you may have a different country on the side. These are rocky waters as they may not have been approved by the ECE, so you may be forced to have them inspected or changed entirely.

Tyre Width

The first number in the key string of numbers on your tyre is the width in millimetres. Tyres come in a variety of widths but your vehicle cannot fit a certain range of sizes before it’s either too big and damages other components, or too small to be stable while driving.

Aspect Ratio

Separated from the tyre width marking with a forward slash, the second number in the sequence is the aspect ratio. A tyre’s aspect ratio is also known as its profile and represents how tall the tyre is in relation to the width. For example, a common aspect ratio is 70, which means that the tyre’s height is 70% of its width. It’s easier to change the aspect ratio when changing tyres, and you can choose between low-profile tyres that allow you to fit larger alloy wheels in, or higher-profile tyres that offer a boost in comfort.

Rim Diameter

Always beginning with an ‘R’, the rim diameter marking gives the correct diameter of the wheel that slots inside the tyre’s centre. This is an important number as you cannot fit a bigger or smaller tyre onto a wheel - if you want a bigger alloy, you need to switch the tyres out for a larger rim diameter. Most vehicle tyres have a rim diameter of 14” to 20”.

Load Index

The last number in the sequence, the load index marking informs you of the maximum amount of weight your tyre can safely take. Adding any more weight past this point is extremely dangerous and could blow out and wreck the tyres. This marking used to be an exact weight figure, but now it is an index number that can be ciphered using a load index table to provide a more consistent measurement.

Speed Index

Lastly, the tyre speed index is a letter which, when put through the speed index table, represents the maximum speed the tyre can handle for 10 minutes. When new vehicles are made, they must be tested for their top speed to be given a speed index, and some cars are purposefully limited to keep within a certain speed index. For winter tyres, the speed index is often reduced by one step.

Driving over this limit for too long can result in dangerous consequences for the tyres and vehicle, such as tyre blowout which could result in serious accidents if you’re going at fast speeds.

This figure is important because when choosing a new set of tyres, if you pick a set with too low a speed index for your vehicle, you could risk invalidating your insurance. However, you may fit tyres that are higher than the speed index. You can find a full speed index table on the AA website.

If you’re looking to find new tyres so that you can up the speed index or change the aspect ratio, LK Performance has the UK’s most trusted selection of replacement tyres for a range of vehicles. Use our online tyre fitment filter and enter your details found on the tyre sidewall markings, and we’ll filter our store to give you only the tyres that fit your vehicle. From there, you can choose between high-quality tyres from pedigree brands including Pirelli, Firestone, Continental, Michelin and Goodyear. Browse our collection today and get a free tyre fitting at our vehicle maintenance centre.