As you drive, tires are constantly being worn down. They should be regularly inspected and replaced when it is time to do so. Tires will wear down at different speeds for different people, based on vehicle type and how the vehicle is driven (speed, driving conditions, maintenance, driving habits, temperature, etc.).
A tire is considered “worn”, or in need of replacement, when there is just 1.6 mm tread depth remaining. To measure this you can do one of three things: buy a tread depth gauge, examine the tire wear bars, or do the penny test.
Tread Depth Gauge
Use a tire depth gauge to measure the tread depth. If there is 1.6 mm or less tread depth remaining – replace your tire.
The Tire Wear Bars
Tires have “wear bars” that help you gauge when the tread depth is less than 1.6 mm. When the tread wears down to a recommended minimum, you can actually see a solid bar of rubber across the width of the tread. If you see this – replace the tire.
The Penny Test
A simpler test involves a penny. Place it into the tread with the Queen’s head down and facing towards you. If you can see the tips of the crown – replace the tire.