Tyre wear differs depending on the position where the tyre is located, so to extend the life of your tyres it is important that you change their positions on a regular basis. Different tyre manufacturers may recommend different rotation periods, though as a general rule you should rotate them every 2,000 - 3,000 miles (approximately 3,000 - 5,000 km).
Tread Wear Indicator
A tyre is a wearing part that will need replacement after a period of time. When the groove depth reaches 1.6mm you are required by law to replace the tyres. It is advisable to replace them before they have reached this limit, to benefit from deeper tread in adverse conditions.