Four season tires are like snow tires in the case of back layer depth. But the features four season tires are lower than a season-specific tire. The durability of these tires is usually between summer and snow tires. They however have the upper hand in the Spring and and Autumn. Because the use of snow tires in the summer will make them wear off easily,they cannot be mixed with four season tires. Yet still the durability of these tires is lower than a summer tire. Usually this is how the tires are that are made for the European market. The tires that are made for the American market or some of the cheap four season tires that have been manufactured by the Chinese may have a higher than average resistance. This feature is gained by lowering the tires’ safety performance and therefore is not used in the European Standarts.
Usually the materials for protecting against attrition for snow tires are lower than the ones used in a Summer tire. For this reason the distance the snow tires can withstand is about %15-30 lower than the ones of a Summer tire. And it will be lower if they are used at higher temperatures than 10 Degrees.
The back patterns of a summer tire, the ridges’ legal value limit is 1.6mm.(TWI – Tread Wear Indicator)The hardening of the tires’ grooves means the tires are worn out. Tires that exceed the TWI Limit are not legal to use and car drivers that are using such tires are immediately punished with a ticket. In the case of an accident,because you were using such tires you may not even be covered by insurance. To be short, you need to check when the tire has been manufactured, if it has been over 10 years the tire may need changing, and it is impossible to say an exact time when a tire needs to be changed, so you need to take it to an expert every year, if not every 5 years.