Question

Tires should be replaced when __________.

Answer 1

Tire Rack's advice is that if rain and wet roads are a concern, you should consider replacing your tires when they reach approximately 4/32" of remaining tread depth." Obviously the tread will wear away over the life of the tire and the volume of its tread grooves will be reduced.

Answer 2

Either when the tire company you use tells you or when they go flat.