The tires are the only parts on your car that have direct contact with the road, which means they have a major effect on ride, handling, braking, and safety. For optimum performance, tires must be properly balanced and inflated, show no signs of physical damage, and have adequate tread depth. In addition, the wheels must be correctly aligned to prevent excessive tread wear that could lead to a flat tire or even a blowout.
Adequate tread depth is necessary for a tire to maintain traction and shed water on wet and slippery roads. You can measure tread depth with an inexpensive gauge available at any auto parts store. Alternatively, you can use the traditional quarter and penny tests.
Insert a quarter into a tread groove with the top of Washington's head facing down. If the top of his head is not visible, your tires have at least 4/32" of tread and are fine for continued use. If you can see above the top of Washington's head, it is time to start shopping for new tires. Take multiple measurements across the tread to help ensure accurate results.
You perform a penny test the same way, except that if you can see above the top of Lincoln's head your tires have less than 2/32" of tread, which is below the legal minimum in most states and cause for immediate tire replacement. Tires worn to this level will also have visible wear indicators (thin bald strips) running from side to side across two or more tread segments.
Tests by a major independent tire retailer found the difference between 4/32" and 2/32" of tread is significant. A pickup truck with 2/32" of tire tread traveling 70 miles per hour took over 499 feet to stop on wet pavement. The same truck with 4/32" of tire tread stopped 122 feet shorter – a 24 percent difference and the equivalent of six or more car lengths.
The company also reported that the tires with more tread exhibited better grip on the road under other driving conditions as well. Given these facts, AAA suggests you put that penny in your piggy bank and instead use a quarter to check tire wear and determine when it is time for replacement.
(AAA Image)
Tire problems to look for while driving
Vibration or thumping:
Unusual vibrations or thumping noises can indicate an out-of-balance
tire, one with tread that has a flat spot due to locking the wheels in a panic stop, or a tire with a separated
belt (see below).
Pull to one side:
While driving at a steady speed, a steering pull to one side may indicate
an underinflated or damaged tire on that side of the car. It could also indicate a brake system or wheel alignment
problem.
Tire problems to look for during inspection
Over inflation:
Too much air pressure causes mostly the tire's middle section to contact the
road. This causes increased wear in the center of the tread, with less wear at the tire's edges.
Under inflation:
Too little air pressure causes mostly the tire's outer edges to contact the
road. This causes increased wear on both edges of the tire tread, with less wear in the center.
Wear on one edge of the tread:
This type of wear indicates worn suspension components or a
wheel alignment problem.
Erratic tread wear:
Alternating high and low spots around the tread, called cupping or scalloping,
may indicate a wheel out of balance, but are more often a sign that you need to replace worn shock absorbers
or other suspension components.
Sidewall cuts and tears:
Impacts with road debris and curbs can damage the rubber tire sidewalls.
You can usually ignore cosmetic damage, unless accompanied by a bubble or bulge (see below). However, if the
cords of the tire carcass are exposed and damaged you should replace the tire.
Bubble or bulge:
A bubble or bulge on the tire sidewall or tread indicates one of the belts
inside the tire has separated from those around it. Replace any tire with this type of damage as soon as possible.
Measuring tire tread depth
Adequate tread depth is necessary for a tire to maintain traction and shed water on wet and slippery roads. You can measure tread depth with an inexpensive gauge available at any auto parts store. Alternatively, you can use the traditional quarter and penny tests.
Insert a quarter into a tread groove with the top of Washington's head facing down. If the top of his head is not visible, your tires have at least 4/32" of tread and are fine for continued use. If you can see above the top of Washington's head, it is time to start shopping for new tires. Take multiple measurements across the tread to help ensure accurate results.
You perform a penny test the same way, except that if you can see above the top of Lincoln's head your tires have less than 2/32" of tread, which is below the legal minimum in most states and cause for immediate tire replacement. Tires worn to this level will also have visible wear indicators (thin bald strips) running from side to side across two or more tread segments.
Tests by a major independent tire retailer found the difference between 4/32" and 2/32" of tread is significant. A pickup truck with 2/32" of tire tread traveling 70 miles per hour took over 499 feet to stop on wet pavement. The same truck with 4/32" of tire tread stopped 122 feet shorter – a 24 percent difference and the equivalent of six or more car lengths.
The company also reported that the tires with more tread exhibited better grip on the road under other driving conditions as well. Given these facts, AAA suggests you put that penny in your piggy bank and instead use a quarter to check tire wear and determine when it is time for replacement.