A small amount of rubber on each tire is what holds your car onto the road throughout all kinds of conditions and obstacles. The design of your tires has evolved over many years by many manufacturers. Here is how your tires keep you safe and what to watch for to know when it's time to replace them.

Tire Design and Safety

Your tires are made of many layers of rubber, metal and fiberglass. The layers hold the tire's shape while allowing it to flex and hold onto the road surface. The sidewalls bend as you go around corners and flex when you hit a bump, absorbing some of the shock. The tread design holds onto the road even when it's wet.

To keep your tire from slipping off of the road, the tread is made up of four important elements:

• Lugs - This is the only portion of your tire that touches the road. As you drive, the rubber in the lug wears down. It is the main gauge of when it's time for a new tire. The lug must work with the other parts of the tread to keep you on the road.
• Voids - This is the space between lugs on the tire. This space allows the lugs to flex back and forth as they hold the tire onto the road.
• Grooves - These are the small open channels that extend across your tire. These push water out of the way of the lug. Without these grooves, your car would hydroplane on top of the water. The lugs would lose their grip on the pavement and you could skid off of the road.
• Sipes - These are additional channels that go across the tire and push more water out of the way. Tire dealers will put these channels in your new tires at your request if you live in a particularly wet climate.

Checking Your Tires for Safety

Make it a habit to check your tires each time you put gas in the car. It takes just a few minutes to find out if your tires are still keeping you safe on the road. Several factors affect how a tire wears, so check each tire individually using on of the following techniques.

• Check the wear bar - Each tire has a small strip of rubber extending across the tire's surface. The height of this strip represents the minimum amount of lug you need on the tire for it to be safe. Compare the height of the lug with this wear bar. If the lug has reached that level or lower, it's time for a trip to the tire store for a new tire. As the lug gets lower, it loses its ability to hold your car on the road.
• Use the penny test - Put a copper penny into one of the voids with Abraham Lincoln's head down into the space. If you can't see the top of his head, you still have a safe amount of lug on your tire. When you can see over the top of his head, it's time to replace the tire.
• Get a precise measurement with a wear gauge - Tire shops have an instrument, called a wear gauge, which measures exactly how much lug is left on your tire. It will help the shop give you an estimate of when you may need to replace the tire. Many tire shops will do this test for you for free.

For more information, contact Collier Goodyear Car Care Center or a similar company.