The confusing world of car tyres explained | Oxfordshire, Lincolnshire, Hertfordshire, Herefordshire & Bedfordshire | Hartwell
Car Tyres Explained

The confusing world of car tyres explained

To the average motorist car tyres are just a means of keeping their vehicle glued to the road. But with tyre manufacturers investing millions of pounds each year into developing new compounds and structures there is far more to tyres than meets the eye.

How to read your tyre sidewall markings

When you are looking to change your tyres you will regularly be asked what size tyres you require. This information can be found on the side wall of your current tyre.

But what do all of these numbers and letters mean? In the diagram below we have labelled each number with a description of what it means.


In the image example the vehicle is running a 195/55 R16 87 V tyre. This means that the tyre is 195mm wide with a 55% aspect ratio. This represents the height of the sidewall as a percentage of the tyre width.

The letter R represents a radial construction meaning the cord piles the tyre has been constructed of are arranged at 90 degrees to the direction of travel. This tyre design was first introduced in 1968 and has remained the same since.

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The number that follows the R represents the tyres diameter measured in inches. In this example the tyres diameter is 16” across.

Your tyre’s load index relates to its maximum carrying capacity (in kg). You’ll find the load rating of your tyre on the sidewall, just to the right of the diameter. In our example above the vehicle has a load rating of 87 meaning the tyre can take up to 545kg of load.

The speed rating is the maximum speed for a tyre when it is correctly inflated and being used under load. The speed rating is the letter at the end of the sidewall, after the load index number. A tyre with a speed rating of V, for example, has a maximum speed of 240 km/h.

When buying new tyres, make sure you match their speed rating with the speed capabilities of your vehicle. Load ratings and speed ratings should be looked at together when you buy a new tyre. Also remember to check your manufacturer’s recommendations.

The differing types of tyres explained

Like everything else in the world, different things come in various types or kind. The same is true of your car tyres. Choosing the right kind of tyre to mount on to your cars wheels is dependent on several factors including the general use of the vehicle and driving conditions, among others.

Whether you are looking for lap time or enjoying a leisurely cruise down the motorway you can find a tyre that suits you and your vehicle best. Here is a breakdown of the different types:

Summer or performance tyres

If there is one thing that defines this class, it’s speed, and wherever speed is involved grip is king. As such these tyres need to offer as much grip as possible. They tend to be made of soft rubber compounds have very minimal tread block patterns or none at all. These tyres are not made to last and as such won’t give great mileage returns.

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Wet weather tyres

If you have a set of summer tyres then there is a high chance you will have a set of wet weather tyres too. Along with the summer tyres wet weather tyres are also constructed from a soft rubber compound, to ensure the tyre can generate heat much quicker than most other tyres as the rainy season tends to be much cooler. They are also heavily grooved to help channel water away from the contact patch of the tyre.

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All-season or All-round tyre

This type of tyre does exactly what it says on the tin. Most vehicles that are produced today are fitted with All-season tyres. This is because they offer you performance, grip, wet weather safety, acceptable noise levels and durability. It is no wonder then that most people choose to use All-season tyres as they are the most practical and mean you don’t need to bother with the hassle of changing them each season.

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Winter tyre: snow and ice or snow and mud

Driving in the winter months can be especially challenging. Putting on the wrong set of tyre compounds can very often going to be a recipe for disaster. There are two different types of winter tyres, depending on the prevailing environmental conditions where you live. If you are largely driving on mud and snow then the M&S (not Marks and Spencer) tyres will suit you down to the ground. If you are however driving on snow and icy roads, then the winter tyres with the snowflake symbol are your best bet. Many of these tyres have metal studs embedded in the tread to offer extra grip on icy roads but do make an awful amount of road noise (these are illegal to use on a public highway in the UK).

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How to check your tyre wear

Your tyres are the only part of the vehicle that actually make contact with the road, so making sure they have right amount of tread is vital. But if you are unsure on how to check your tyre tread depth, this is how to do it:

  • Firstly make sure your vehicle is parked with the handbrake on and ignition off. Turn the steering wheel to full lock for a full view of the tyre.
  • On the sidewall of the tyre look for the letters TWI (Tread Wear Indicator). Be wary as some tyre manufacturers might use different symbols so always check.
  • Above the letters TWI you will see little blocks, these are the Tread Wear Indicators. If the tread is level with the indicators, it is at its legal limit meaning a tyre change is required immediately.
  • The legal limit for tread depth is 1.6mm but for yours and your families safety we would recommend changing your tyres when the depth gets to around 3mm remaining.
How can I check the exact level of my tread I hear you ask?


The easiest and most straight forward way is to use a trusty old 20p piece. The bevelled edge of a 20p coin is 3mm deep. If you cannot see the edge, the tread is okay.

Make sure when you are checking the tread that you check all four tyres and several different areas of the tyre. Pay particular close attention to both the inside and outside edges as they can sometimes wear unevenly due to bad wheel alignment.

If you don’t feel comfortable checking your vehicle yourself or would rather one of our highly trained technicians do it for you, you’ll be pleased to hear we are offering seasonal checks from as little as £30.

Book your check today