Tyre labels: Everything you need to know

Decoding tyre labels: What you need to know

• Understanding tyre size and specifications

  The string of numbers and letters underneath the supplier’s name on the tyre label is known as the size code.

  So, how do you crack it? For demonstrative purposes, we’ll look at an example code: 205/55R16 91V. We’ll break it down into its five separate parts - and explain what each section means:

  The first part, 205, refers to the tyre width, and is measured in millimetres.

  The second two-digit number, 55, is the aspect ratio. This is calculated as a percentage, meaning the tyre’s height is 55% of its width.

  The ‘R’ means the tyre has a radial construction, as opposed to ‘B’ (bias-ply) or ‘D’ (diagonal).

  The following number, 16, denotes the diameter of the rim in inches.

  The next figure, 91, refers to the load index, which is how much weight each individual tyre can carry when at full pressure. This load index figure needs to be checked against a tyre load index chart to get the weight in kilograms.

  The final letter, ‘V’, is the speed rating, which denotes how fast the vehicle can go when it’s carrying its maximum load. You can check this against a tyre speed rating chart to get the corresponding mph figure.

  It’s important to understand your size code. If you don’t, you could buy unsuitable tyres and/or drive unsafely. For example, you could drive faster than your speed rating allows, or load your vehicle with more weight than it can cope with. This could damage your car and its tyres, compromise your steering and braking – and increase your risk of having an accident.

• Fuel efficiency and rolling resistance

  This section of the tyre label features a grading (from ‘A’ to ‘E’) with a corresponding colour coding. ‘A’, at the top, is green, and ‘E’, at the bottom, is red. An A-rated tyre has low rolling resistance, whilst an E-rated tyre has high rolling resistance. So, what does this mean, and how does it relate to fuel efficiency and the environment?

  Put simply, rolling resistance is the amount of energy a car uses to travel a certain distance. The lower the rolling resistance, the less energy is required, which means less fuel consumption, fewer CO2 emissions and more financial savings for you.

  On the other end of the scale, higher rolling resistance tyres require more energy, more fuel - and cost more, whilst generating more CO2 emissions!

  Using lower resistance tyres can save you up to 2% on fuel over their lifespan, according to some estimates.

• Grip and safety in wet conditions

  The wet grip rating also uses an ‘A’ to ‘E’ system, only with a dark blue to light blue colour scheme.

  ‘A’ denotes the shortest stopping distance and ‘E’, the longest. The difference between each level is around half a car length, or 2.5 metres’ stopping distance in wet conditions.

  Therefore, a car with A-rated tyres has a stopping distance of 10 metres less than a car with E-rated tyres. It’s not just stopping distance that makes a difference when driving in wet conditions, either. Good wet grip tyres also make cornering and handling easier, which improves your overall driving safety.

  Higher-rated tyres can be pricier, but it’s worth paying a little extra, as the increased stopping distance and improved handling could make the difference between having an accident and narrowly avoiding one.

Load index and vehicle suitability

You can check your vehicle’s load index on the tyre label or the sidewall of your tyre. It may also be listed in your owner’s manual.

Once you know your load index, you can convert it using a tyre load index chart, then multiply this number by four. The figure you arrive at should be equal to or higher than your gross vehicle weight rating (GVWR), which you can find in your owner’s manual.

Larger vehicles, such as trucks and buses that have a dual load index (two tyres on each axle) will have a different size code load index than that of cars. In the example 115/113R, the first number is the load index of the tyre when used on its own, whilst the second is the load index when both are used together. The ‘R’ stands for ‘reinforced’.

You may also see ‘XL’, which means ‘extra load’. To work out the load index of a heavy-duty vehicle, follow the steps above, but refer to a dual index chart.

Choosing a lower load index than your GVWR can cause tyre damage and/or blowouts, poor handling and stability - and potentially, a road accident. It’s also illegal; you could receive a Fixed Penalty Notice (FPN), points on your licence, or a fine.

Speed ratings and performance

The speed rating on your tyres has a big impact on how well your car handles and performs. Higher-rated tyres are specially constructed to deal with the increased heat that’s generated at faster speeds, as well as the more precise steering response that’s needed. They’re also more robust, to cope with the additional wear and tear associated with high-speed driving.

However, if you tend to drive shorter distances and at lower speeds, tyres rated at the other end of the scale could suit your needs.

Either way, it’s important to choose tyres with the right speed rating for your car. Going too low could negatively affect the steering and handling - and could even cause a blowout or an accident. Go too high and you may find that your car isn’t performing as well as it should. Your tyres might wear out faster, too.

Noise levels and comfort

The external noise level section of the tyre label is represented by a loudspeaker icon with one to three sound waves, as well as a numerical decibel level (typically from 67 to 77 dB) - and a rating from ‘A’ to ‘C’.

The quietest tyres have a lower dB level, one sound wave and an ‘A’ rating. The loudest have a higher dB rating, three sound waves and a ‘C’ rating. Three sound waves also means that the tyres exceed the EU-regulated noise limit.

Quieter tyres are more suited for driving in built-up urban environments and areas where noise pollution controls are in place. They also provide a more pleasant driving experience. Even on motorways, quieter tyres are a better choice because excessive noise can cause stress and loss of focus on long journeys.

Purchasing new tyres: What to ask and look for

Before you buy new tyres, be clear in your mind about your driving style, what you use your vehicle for, how frequently you use it, and whether you predominantly drive on motorways or built-up roads.

You should also make a note of the load index and speed ratings on your current tyres. It’s a good idea to set a budget, so you’re not tempted to spend more than you intended.

Ask the vendor to talk you through everything on the tyre label, including fuel efficiency, the wet grip and external noise rating, load index and speed rating. You can then decide whether the tyres match your car and suit your needs.

You should also ask about the expected mileage and durability of the tyres, along with the warranty. Some retailers provide installation, balancing and alignment services with tyre purchases – and they may even dispose of your old tyres, so don’t be afraid to ask.