Drivers should generally replace their cars' tires every six to 10 years, depending on manufacturing recommendations. Tread wear, exposure to outdoor elements and tire age are three factors to consider when questioning whether vehicle tires should be replaced.
Tire tread is important because sufficient treads grip the road better, while insufficient treads respond poorly in rain and snow. An easy test for tread wear is placing a penny head first into multiple tread grooves across the tire and if the top of Lincoln's head is visible, the treads are worn. Exposure to extreme heat and sun may cause structural damage to the tires.