All tires lose air, so check your tires monthly. Always use the same tire pressure gauge and check the air pressure first thing in the morning, not after you've driven on them or they've been sitting in the hot sun. Inflate to the pressures listed on the carmaker's decal (on the driver's door or jamb), NOT the maximum pressure listed on the tire. The recommended tire pressure is based on the weight of your particular vehicle, not the tire brand or tread style.
Forget about the penny-in-the-tread trick. A tread depth gauge only costs a few dollars and is far more accurate. Measure the tread depth about 1 in. from each edge and the depth of the center tread. They should all be the same. If they're not, refer to the section on Diagnosing Tire Problems below to find the problem and the fix.
The front tires on front-wheel-drive cars carry a heavier load and perform more work (steering and braking). So they wear faster than the rears. Rotating tires every 6,000 miles spreads the wear across all four tires. Skip it and you'll find yourself with two bald tires in the front and two halfway good tires in the rear. You'll lose about 25 percent of the tire set's life.
Most drivers ignore their tires until it's too late. Then they have to spend big bucks to replace them. However, you can diagnose tire problems and correct them early by performing three critical maintenance chores: checking the tire pressure, measuring the tread depth regularly, and rotating tires every 6,000 miles.
Never assume that the maximum air pressure shown on the tire's sidewall is the same as the recommended tire pressure. Filling to the maximum pressure always means you're overinflating your tires. The recommended tire pressures for your car are printed on the driver's door or doorpost decal.
Although overinflated tires may give you slightly higher gas mileage, they can cause much more serious problems than they solve. Overinflated tires carry the entire weight of the car on the middle portion of the tread. On wet roads, the center tread can't pump the water out to the sides (think of a squeegee with a bulge in the center). So they're more prone to hydroplaning (like water skiing) and also more likely to skid in a stop or in a turn, and blow out on hard bumps. The bottom line: Overinflation is foolish and dangerous. Always follow the inflation pressures shown on the car, not the tires.
The center tread puckers toward the rim because there's not enough pressure to keep it in contact with the road. So the full weight of the car rides on the edges. In addition to premature wear, low tire pressure causes excessive heat and possible blowouts. The owner of these tires never bothered to keep the tires inflated.
The higher pressure ballooned it into a doughnut shape. Only the center tread was in contact with the road. That's why the center tread wore more than the edges. This owner was diligent (but mistaken) about filling the tire to its maximum inflated pressure. Driving on overinflated tires is costly—and dangerous.
Fill Tires With Nitrogen—Or Not?
Some dealers now offer to fill tires with nitrogen instead of regular air for an additional charge. Nitrogen leaks less than compressed atmospheric air (because nitrogen molecules are larger than oxygen molecules) and reduces rubber oxidation. But that doesn't mean nitrogen never leaks. The problem is that once you commit to a nitrogen fill, you must stick with it for the life of the tire. The instant you add compressed air, you negate all the benefits.
Since you still need to check and refill your tires, and since nitrogen is hard to find, you'll be married to the dealer forever. That's good if they offer free coffee and doughnuts while you wait, but bad if they're not conveniently located. Even though nitrogen really is better than regular old air, it's doubtful you'll ever see enough of a benefit to justify the investment. Your tires will probably wear out from normal driving long before the important benefits of nitrogen really kick in. But if you drive less than 5,000 miles per year and plan to keep your tires for 10 years (and don't mind hanging out at the dealer), nitrogen is definitely worth it. By the way, the green caps on tire valve stems indicate the tire is filled with nitrogen.