1. Understand that the primary func

1. Understand that the primary function of tread on a tire is to divert water from beneath the tire to improve traction and avoid hydroplaning on wet roads. Tires become unsafe when they're worn, and once the tread is down to 1/16th of an inch (1.6mm), the tire is no longer safe.

2. Look at the tread pattern. All tires sold in the United States and other countries have what are called "tread wear bars". These are small bridges that form between your treads. Look at the tread pattern and you'll see the beginnings of these bars start to form between the treads, or running across the tires. As the tires wear, these bars will become flush (level or even) with the tire's tread. At this point, it's time to replace the tires.

3. Check the tread by using the "penny test." Take a penny, and place it upside down with Lincoln facing you in the center of the tread (at the thickest part of the tire).

4. Use a tread depth indicator or gauge. Obviously, not everyone can get hold of an Abraham Lincoln penny. Either use the tread pattern test, or resort to using a special tread depth indicator or gauge tool to measure your tire's tread. If you don't already own one, the gauge is cheap to purchase from an auto parts dealer and it's easy to use.

5. Know the legal requirements. Worn tires should be replaced as a matter of common sense to assure safety, but in some jurisdictions, there are also legal requirements to replace worn tires. In many US States, tires are considered to be legally worn out when they have worn down to 1/16" (1.6mm) of their remaining tread depth. In the UK, the minimum depth of the tread on tires (tires) is 1.6 millimeters, across the central ¾ of the tread around the whole tire (tire).

6. Make note of any irregular tread wear. This could indicate a wheel misalignment, the need for a tire rotation, or both. Uneven tread wear is a sign that you need to take your car in for servicing.

7. Replace the tires at least every 6 years. If you're not sure, the minimum replacement time that is recommended by the NHTSA is six years regardless of use, with 10 years being the maximum service life for tires. Check your owner's manual for specific recommendations related to your car. And always err on the side of caution if you suspect your vehicle has tires that are over six years of age.