Performance, reliability and safety are often the most important factors people consider when buying a car (besides the price of course) and rightly so, as it is a huge decision to make. There is one motoring safety decision however that is sadly often overlooked but is arguably the most important safety feature of your car – the tyres!
Most people will do the bare minimum to ensure that their tyres will pass the next M.O.T and change them when the tread is approaching the legal limit, but with winter fast approaching, what tyres do you go for? With over 300 brands and thousands of patterns to choose from, it can be a bit of a headscratcher to make an informed decision. Are winter tyres worth it? Can I also use them in the summer? In this blog we hope to answer all of these questions and test out exactly how well different varieties of tyres perform!
The differences between seasonal tyres is not only in the tread, they are made from an entirely different rubber compound that behave differently depending on the temperature.
If you take a closer look at winter tyres, there is a lot of space between each tread line and it will often feature a very different pattern. This void between the tread line allows the tyre to pack in snow and water so when the wheel rotates it can maintain sufficient grip with the road. The rubber compound in winter tyres is much softer than in summer variants as when it gets cold, the rubber will harden. If summer tyres are used in winter, they not only struggle to provide sufficient traction due to the tread pattern but the harder rubber becomes so stiff, it makes it more difficult for the tyre to ‘bite’ into the road.
Summer tyres are built with the opposite goal and comparatively have much smaller gaps between the tread lines to get as much surface area as possible on the tyre in contact with the road to provide traction. Winter tyres are not recommended for use in the summer as the softer compound will wear out very quickly, and it is less safe than a more climate appropriate tyre.
There are several different types of tyres available on the market designed for specific seasons, as well as an ‘all season tyre’ which is popular in the UK. All season tyres are designed to offer a compromise between seasonal performance without being particularly dangerous in one weather condition.
One thing to consider when dealing with a separate set of winter & summer tyres is the storage when a set is not in use. When tyres are not in use, they must be stored appropriately to ensure that they are not warped by being left standing upright or left out in the rain. Always rack them up, indoors. Some businesses will offer to 'garage' your spare tyres for you for a small fee.
So, what time of year is best to change tyres? If you are considering changing tyres from summer/ all season to winter tyres, the industry uses the ‘seven degree’ rule as a rough guideline for when is the best time to make the switch. This does not mean that as soon as the temperature in the morning reaches 7°C or less – it in fact refers to the average weekly temperature in your region reaches below 7°C. When this happens, you should start thinking about making the switch as frost is much more likely in the cold & dark mornings & evenings.
For many years the exact temperature of when winter tyres becomes more effective has been a bit of a mystery, however YouTube Channel Tyre Reviews has created an in depth experiment at a specialist indoor testing track, where not only the moisture level but also the air and ground temperature can be controlled, giving us an in depth look at how each tyre performs under drastically different weather conditions. A variety of tyres were used on the same car; the tyres tested are as follows.
When you are lucky enough to have an indoor snow handing test track, the first test can only be a straight race around it the entire course. This test took place within a specialised indoor environment that ensures the temperature stays around -9°C / 16°F and so there was plenty of snow on the ground. This test gives a great insight into how a normal driver would traverse the same conditions and how each tyre performs in heavy snow.
As you can expect, the winter biased tyres offer more grip around the corners and so are easier to drive quicker around the track. Unsurprisingly the Nordic tyre is specifically designed for these conditions and so performed the best offering plenty of traction throughout the test. The summer variants begin to struggle and are much more difficult to control and tends to slip forcing the driver to slow down.
The dry brake test is used to measure the emergency stopping distance from 80kph (50mph) of each tyre at a number of different ground temperatures ranging from 8°C to 0°C. Here are the results;
Here is an exact breakdown of the data from the test results: The distance of each stop is measured in metres.
8°C / 46°F
5°C / 41°F
2°C / 35°F
0°C / 32°F
As we can see, unsurprisingly the warm weather biased tyres perform the best in this experiment, particularly in the warmest temperatures. The largest gap between the best and worst performer came in at just over 6 metres difference!
The final test takes the same format and speed as the dry brake test 80kph (50mph) but in wet conditions and across a wider range of road temperatures. It is interesting to note that when the ground was set to the colder 2°C/ 35°F temperature, the moisture was beginning to form a slight frost that turns the road a greasy surface we are very used to seeing in the winter time.
As you can see from the graph there is a sharp improvement of the summer tyres performance as the temperature gets warmer, however the summer and Nordic tyre are blown out of the water when it comes to stopping distance as there is a 7 metre gap between the best and worst performing tyre at 2°C. This is a colossal distance and can mean the difference between stopping safely and causing a serious accident when it comes to real driving! If you ever needed proof that climate appropriate tyres are very effective, look no further!
Here is a further breakdown of how each tyre performed. Once again, each stopping distance is measured in metres.
6.5°C / 44°F
9.8°C / 50°F
15°C / 59°F
If you are the kind of motorist that typically overlooks your tyres when taking safety into consideration, this data speaks for itself in determining how dangerous summer tyres can be in the winter and wet weather. According to the data the 7°C rule is not without merit and appears to be a sensible time to consider removing the summer tyres if you are using them.
One of the most important things you can do if you are concerned with improving your stopping distance is to ensure that you always keep a safe distance away from the car in front, ensure that you have appropriate tyres for your local climate and that those tyres have plenty of tread left on them. The legal limit in the UK for tyre tread depth is 1.6mm, which is not much at all and I would highly recommend new tyres if you are approaching this limit – especially in the winter!
To see the full tyre test in action, check out the full video on Tyre Reviews’ Channel here.