Why not just drive with your winter tyres in summer? Then you don't have to pay for two sets of tyres and for changing them. The reason is simply that it’s dangerous – you're putting your safety, that of your passengers and other drivers at risk. Tyres are a major factor in how safe your car is to drive. So what's the difference between summer tyres and winter tyres then?
The rubber compound
The amount of rubber used in winter tyres helps the tire stay soft and flexible so it can grip the road when it's cold outside. If you drive on winter tyres in the summer, then your tyres will be too soft, which means they will wear faster, reduce fuel efficiency and also need a greater distance for braking. The reason for this is because winter tyres are more pliable at higher temperatures, so they wear more quickly on hard, dry asphalt.
The rubber compound used in summer tyres is considerably harder than it is in winter tyres so they can handle the heat of summer. If you drive in the winter with summer tyres, stopping distances will be longer and it will be harder to drive in a straight line because the tyres aren't soft enough to grip the road. If you're even able to get going, that is...
Summer tyres have large contact patches which give the car a better grip on the road. Although the tread pattern has fewer grooves and sipes (thin slits that cut across the rubber) than that of winter tyres, the grooves are bigger so they can move large quantities of water away to the sides, maximising the contact with the road in order to avoid hydroplaning.
Winter tyres, on the other hand, have a lot of grooves, which are also deeper than those in summer tyres. It is these grooves that allow winter tyres to keep their traction on snow and ice. There are also smaller channels called sipes that help the grooves keep the tyre in contact with the surface.
Experts agree: Winter tyres are just for winter. But when should you change your tyres? Whenever the temperature consistently stays below 10 degrees celsius is when you need to use your winter tyres. The rule of thumb is that below 10 degrees is when winter tyres do best on the road and above 10 degrees is when summer tyres do best.
In general, you should get new tyres when your tread is worn down. The legal minimum tread depth for cars in the UK is 1.6mm throughout a continuous band comprising the central three-quarters of breadth of the tread and around its entire outer circumference.
A quick and easy way to see if your tyre tread exceed the minimum legal tread depth is to take the 20p test. Simply place a 20p coin into the main tread grooves of your tyre. If the outer band of the 20p coin is obscured when it is inserted, then your tread is above the legal limit. If the outer band of the coin is visible, then your tyres may be illegal and unsafe and should be checked immediately by a qualified tyre professional. When taking the test, remember to check at least three locations around each tyre. As the test is so quick and easy, stay safe by checking your tyres at least once a month.
A lot of drivers don't know that tyres age even if they aren't being used. UV rays, humidity and temperature all degrade the material. This is why you should buy new tyres every eight years even if you have plenty of tread left.
Remember, drivers whose tyres fail to comply with the minimum tread depth requirements risk a fine of up to £2,500 and three penalty points for each illegal tyre.
The correct air pressure is determined by car manufacturers and tyre makers. You can consult a tyre pressure chart – usually located in the car's door, but always in your owner's manual – to find the right tyre pressure for your tyres. Tyre pressure depends on the type of vehicle you have, the type of tyre and the load. You should check your tyre pressure regularly, especially before you take any long trips.
Hydroplaning is something everyone worries about. It happens when there are large amounts of water on the road that the tyres aren't able to displace. Water is pushed under the tyre, creating a thin film that separates the tyre from the road surface, causing it to lose traction. This results in a loss of steering and braking ability. Tyres more likely to hydroplane are ones that are especially wide (they have more water to push away) and tires with a worn tread. When there is little tread left, the grooves fill with water so the tyre can't displace the water. The same thing can happen if the tyre pressure isn’t right.
What should you do if you suddenly find yourself hyrdoplaning? Take your foot off the accelerator, but do not brake. Avoid steering and disengage the clutch if your car is a manual. Wait until you feel the tyres reconnect with the surface of the road.