How to Know when Car Tires Need Replacing

Author: Andrew Everett / Source: wikiHow

Ever wonder if it’s time to replace your worn car tires? The performance of your tires is very important for maintaining the safety, performance, and efficiency of your vehicle. But at some point, your tires will start wearing out and lose their traction and braking ability.

Luckily, if you’re wondering when to start looking for new tires, there are a few tips that can help keep you in the know.

1 Check your state or region for tread recommendations. The primary function of tire tread is to divert water from beneath the tire to improve traction and avoid hydroplaning on wet roads. Once the tread is down to ²⁄₃₂ inch (0.16 cm), the tire is no longer safe and illegal in most areas of the world. Look at your state or region’s tire tread requirements provided by the transportation department.^[1]
- Call or email your country’s department of transportation or visit their website to locate tread laws.
- In some U.S. states, tires are considered to be legally worn out when they have decreased to ¹⁄₁₆ inch (0.16 cm) of their remaining tread depth.
- In the U.K., the minimum depth for tire tread is 0.0456 inches (1.16 mm) across the central 3/4 of the tread around the whole tire.
2 Replace your tires if the tread bar is flush with the tire tread. All tires sold in the U.S. and most other countries have tread wear bars—small horizontal bridges that form between your treads at a lower depth. As your tires wear, these bars become flush with the tread. When the tire tread is even with these wear bars, it means the tread is worn to ²⁄₃₂ inch (0.16 cm) and needs to be replaced immediately.^[2]
- When you look at your tire wear bars, be sure to look at the entire surface of the wheel and not just one isolated location.
3 Check the wear of your tread quickly by inserting a Lincoln penny into it. Take a Lincoln penny and place it upside down with Lincoln facing you in the center of the tread at the thickest part of the tire. If you can see the very top of Lincoln’s head or the copper above it, replace the tire immediately.
If you cannot see the hair on the top of Lincoln’s head—meaning the tire tread is at least as deep as his forehead—your tire does not need replacing yet.^[3]
- If you have a Canadian nickel, insert it between the tread with Queen Elizabeth’s crown facing down. If the top of her crown is visible, the tire is below ²⁄₃₂ inch (0.16 cm) and needs to be replaced.
- Tires do not wear evenly, so be sure to insert the coin at several points from the outside to the inside of your tires. Tires generally wear more on the inside, but over-inflated tires will wear more in the middle.
- For a more accurate tread depth measurement, use a tread depth gauge.
4 Use a tread depth indicator for a more accurate measurement. Place the probe of the indicator in the center of one of the tire grooves on the outskirts of the tread. Remove the gauge by the barrel—taking care not to touch the probe—and note the tread depth….