When it comes to changing between winter tyres and summer tyres, most people are always told to do so when the temperature drops or rises (depending on which season you are entering) 7 degrees.
But is this solid advice, or a misunderstood technicality? To put driver’s minds at ease, we answer the most common questions regarding tyres and the “7 degree rule”.
Is it true that winter tyres should be installed when the temperature drops below 7 degrees?
Yes. This is because winter and summer tyres use different compounds to adapt to the average temperature of each season. Winter mixtures, for instance, operate better below 7 degrees.
Why do some people claim that the “7 degrees rule” is a lie?
Some drivers say that the “7 degrees rule” is a marketing ploy to increase the sales of winter tyres. Many drivers do not realise the different rubber mixtures are designed for the temperature, in addition to the different tread designs and parameters.
Where did this claim come from?
The claim that the “7 degrees rule” is false first appeared as a result of a test in the “Stern" weekly magazine (48/2005). The study has shown that summer tyres have a shorter braking distance in temperatures between 0 and +7 than winter tyres. However, this does not contradict the “7 degrees rule”. Rather, winter tyres have many additional parameters to consider, such as braking in snow and slush, that summer tyres are not designed for.
The 7 degree rule is an effective way to indicate when winter and summer tyres are most effective
How should I interpret the results?
It should be highly stressed that the test didn’t conclude that all winter tyres have a longer braking distance, compared to summer products. The test showed that, in certain conditions, certain models of summer tyres offer a shorter braking distance when compared to certain winter tyres.
As a finished product, a tyre will always be a compromise of various performance characteristics. Some tyres have longer durability, while others favour stronger grip. As such, it is not easy to directly compare to very different tyres through one characteristic of their performance.
There are, of course, winter tyres that will perform well on dry surfaces in temperatures as high as 10 degrees. Similarly, there are summer options that offer a good level of safety in temperatures close to zero. However, this is only specific products, not a hard and fast rule.
If, on the other hand, you want a product that can cover a broader range of temperatures on either side of 7 degrees, you may want to consider all-season tyres. These tyres offer a compromise between the other products. While they don’t perform well in the hottest or colder environments, they offer a mix of performance parameters to cope throughout the year.
Why should I use winter tyres?
Because winter tyres use numerous technical solutions that enhance their safety in the winter - such as special tread patterns, more sipes, higher tread, etc.
And what if the 7 degrees rule is a marketing ploy?
This is a logically false claim.It would be easier and cheaper for the tyre manufacturer to produce a single type of tyre.This would reduce the costs of manufacturing seasonal tyres.And the number of tyres sold would not change.Driving all year round on just one set of tyres, we would have to buy new tyres just as often.By producing just one type of tyres, the income would be higher, as the cost of production would drop.