Tyres must be replaced once they achieve their tread don indicator or show signals of harm like cuts, bulges

http://wheelbaseywcq415.wpsuo.com/understanding-tyres-for-suvs-vs-passenger-cars-in-perth-a-detailed-comparison

Tyres should get replaced every time they attain their tread have on indicator or exhibit signs of damage such as cuts, bulges, or uneven use