In countries such as Germany, Sweden and Austria, winter tyres are, as you may expect, compulsory during winter months. However, while not mandatory for UK drivers, motorists here may still want to think about investing in some. We take a look at how winter tyres work and why drivers may benefit from a set when the mercury drops. The main difference between winter tyres and regular tyres is the tread depth. On a winter tyre it starts at between 8 and 9mm, as opposed to 7 and 8mm on a regular tyre.