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Tyre sizes explained - everything you need to know

What are tyre sizes? How do you read numbers on the sidewalls? Here's everything you need to know about those black and round things on your wheels

How to choose the right tyres for your car

Choosing new tyres isn’t just about getting the cheapest set for your vehicle. Your tyres have a crucial effect on how your car steers, brakes, accelerates and feels on the road. Simply put, they’re pretty important.  

Car owners have a bewildering choice of types and sizes of tyres to choose from. When it comes to replacing one or more tyres, how do you decide which to buy? The answer depends on your car, how you use it and what the road conditions are like where you live.

Get the right size tyres

The first problem is getting the right size tyre. It’s very important to match them to the car manufacturer’s recommendations and to match the tyres on the same axle.

Every car tyre has a standard code written on the side. It looks like something like this:

165/50/R 1596H

In this example, the various numbers and letters mean:

·       165 - the tyre width in millimetres

·       50 - the ‘aspect ratio’ or profile of the tyre. Shorter sidewalls look sportier and increase cornering grip – but are generally pricier and provide a less comfortable ride.

·       R - stands for radial. Most car tyres now have a radial construction – decades ago they were more likely to be cross-ply. Radial tyres are stronger and it’s important to match all your tyres to the same construction.

·       15 - describes the diameter of the wheel rim in inches

·       96 - is a load rating. This refers to the weight in kilos that the tyre is capable of supporting. For normal cars this is unlikely to be a significant factor.

·       H - is a maximum speed rating. Your tyre dealer can explain what the ratings are – almost all the tyre limits are well in excess of the national speed limit though. For normal driving it shouldn’t be something to worry about.

What type of tyre is best?

As well as the exact size and speed ratings, there’s a choice in what seasonal tread pattern is best for your driving style.

·       Summer tyres – Have a simple tread designed to perform best above 7 degrees on wet or dry roads. The softer rubber of summer tyres gives better fuel economy and grip in warmer conditions.

·       Winter tyres - Marked with a snowflake symbol. They perform better in colder conditions, particularly snow. In the UK’s climate, they are considered specialist tyres for season use only.

·       All-season tyres - Usually considered the best option for general motoring in the UK. They are made of an intermediate type of rubber, which doesn’t go too hard in cold conditions as a summer tyre does. The grooved tread pattern is also designed to avoid skids and aquaplaning on very wet roads.

Big brand or budget tyres?

The famous tyre brands produce premium tyres that are generally higher quality – and more expensive. If it has a name you recognise it usually means a tyre will last longer, grip better and give maximum fuel economy.

Mid-range tyres may have less familiar brand names but less intimidating prices too. The blend of affordability and mid-range quality may be perfect for an average family commuting car.

Budget tyres will be the cheapest on offer and they can work perfectly well. They may last half as long as a premium tyre though and will not provide the finer points of handling that a sports or luxury car may offer.

Where to buy tyres

If you aren’t sure about tyres, don’t try to save money by ordering online. Drive to a tyre specialist and ask for their advice. They will normally give you a choice of premium, mid-range and budget tyres, and will be able to match size and style with what’s already fitted to the car.

They may persuade you to spend a bit more – but their reputation depends on not fitting the wrong tyres to a customer’s car. All tyres sold in the UK will meet strict safety standards too. The main difference will be in performance at the handling limits and in how long they last.

Looking after tyres

Keeping the correct air pressure in a tyre is the best way to prolong their life. When you check the tyres have a quick look for uneven wear or blemishes. It could be that your wheel alignment or tracking needs adjusting – this will help your tyre life too.

Some car owners go to tyre centres and have their tyres rotated onto different wheels regularly. It helps keep the wear even across a set of tyres. It’s probably only worthwhile with premium brand tyres.

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