Time for a pop quiz.

  1. When is the last time you checked the air pressure on every tire on your car?
  2. When did you last check the air pressure on your spare?
  3. What is the proper pressure to which your vehicle’s tires should be kept inflated?
  4. Is that number the “maximum psi” imprinted on each tire’s sidewall, or should it be a different pressure?
  5. Should you keep all four tires inflated to one pressure, or is it different for tires mounted on your front and rear wheels?
  1. When did you last rotate your car’s tires?
  2. When did you last do a four-wheel alignment on your car?
  3. Would your car’s tires pass the “penny test” or the new “quarter test”?

OK, pencils down.

So how’d you do? Think you got all of the answers right? Did any of these questions stump you? Are you happy or unhappy about how you did?

The good news is that if you didn’t do as well as you thought you should, this quiz will not earn you a letter-grade and you needn’t worry about having, “See me after class” scribbled in red ink on top of your answer sheet. But the bad news is that you’ll be the one who’ll be driving in your car later today — either alone or with your friends or family.

The Rodney Dangerfield of auto components

“One of the most common things that we see at our service centers is that people are not maintaining proper tire pressure in their tires,” says Matt Edmonds, vice president of Tire Rack, an independent tire tester and retailer of tires, wheels and performance accessories. “With today’s radial tires, you can literally have a tire that’s down in terms of pressure by up to 25 percent, yet, visually, that won’t even be noticeable.”

But based on the company’s experience — a team of drivers test tires from every major tire manufacturer on a state-of-the-art, 10-acre test facility at the company’s headquarters in South Bend, Ind. — when a tire is underinflated by a mere 10 percent, it is likely that it has suffered some degree of internal damage.

There’s really no way to tell how much damage was done without dismounting that tire and looking inside, says Edmonds. “And if you did that, you’d likely find that the tire’s inner liner has started to crumb and that an accumulation of rubber power has started building up inside of the tire. When you reinflate such a tire, everything might look OK from the outside, but the damage has been done on the inside.”

That is why the Rubber Manufacturers Association, or RMA, places such an emphasis on its consumer tire-education program, says Dan Zielinski, senior vice president of public affairs at the Washington, D.C.-based national trade association for the elastomer products industry. He says an easy-to-remember handy acronym — PART — explains the four essential elements of tire care: pressure, alignment, rotation and tread.

P is Pressure

Tire pressure is critical to tire safety and longevity. When a tire is properly inflated, you not only optimize your vehicle’s safety but also save money at the gas pump, and you help make your tires last a whole lot longer. Drivers should check their tire pressure at least once a month with a quality tire gauge and ensure that every tire on their vehicle — including the spare, if so equipped — is properly inflated, says Zielinski. And it’s best to check tire pressure “cold,” early in the morning, before the car has been driven.

Your vehicle’s proper tire-inflation pressure is listed either in the owner’s manual, printed on a special label on the driver’s door, or displayed within a special label in the driver’s doorjamb, or B-pillar. The maximum psi imprinted on a tire only denotes the maximum safe pressure for that tire. It is not your vehicle’s proper tire-inflation pressure.

“Proper tire pressure provides you and your vehicle with improved performance,” says Edmonds. “We’re not talking about high-speed driving and performance in that sense of the word, but rather the ability of your tires to allow you to better control your vehicle, particularly in emergency situations — emergency stops, avoidance maneuvers and good traction on a wet road.”

Underinflated tires make a vehicle react slower because the tires are not well supported by their sidewalls, he says, noting also that underinflation can lead to a situation where the car is more easily upset, causing it to pitch more whenever you change direction. In addition, when a car’s tires are underinflated, normal driving can build up much more heat inside the tire. Excessive heat deteriorates components within the tire and its sidewall and can lead to catastrophic tire failure, a blowout, as well.

Since 2007, the U.S. government has mandated all new vehicles have built-in tire-pressure monitoring systems, but these systems typically warn of a tire-pressure drop of 20 percent from its recommended pressure.

A 20 percent to 25 percent decrease from a recommended pressure of 32 psi is significant. That’s 8 pounds of pressure — past the point of likely tire damage, says Edmonds. “So, even if your car has tire-pressure monitoring, it’s still a very good thing to check your tire pressure on your own with a quality gauge at least once a month.”

A is Alignment

Often referred to simply as a “wheel alignment,” this procedure actually includes measuring and adjusting suspension angles and suspension components, Edmonds says, and greatly influences the operation of the vehicle’s tires.

Out-of-alignment means the suspension and steering systems are not operating at the proper angles, conditions often caused by normal spring sag or suspension wear in the ball joints and bushings, for example. On older vehicles, impact with a pothole or curb often is the cause.

Incorrect alignment settings will usually result in more rapid tire wear. Therefore, alignment should be checked whenever new tires or suspension components are installed and anytime unusual tire-wear patterns appear. “And alignment should also be checked after the vehicle has encountered a major road hazard or curb,” says Zielinski.

The different types of alignment offered today are front-end, thrust-angle and four-wheel. During a front-end alignment, only the front axle’s angles are measured and adjusted. Front-end alignments are generally fine for vehicles with a solid rear axle.

On vehicles with four-wheel independent suspension or front-wheel-drive vehicles with adjustable rear suspensions, the appropriate alignment is a four-wheel alignment. This procedure squares the vehicle like a thrust-angle alignment and includes measuring and adjusting the rear axle angles as well as the front.

R is Rotation

Rotation is also important. Tires generally need to be rotated every 5,000 miles to 8,000 miles. Tires tend to wear differently at each point on a vehicle, and when you rotate your tires properly and according to a set schedule, you promote even wear, getting the most out of your tire investment.

Front- and rear-wheel drive vehicles need to have their tires rotated differently, though, and these recommended tire-rotation patterns vary even more if you are rotating a fifth tire — a full-size spare — regularly. For complete instructions and illustrations concerning proper tire rotation, Edmonds encourages readers to visit the Tire Rack’s consumer information page.

T is Tread

You should also carefully examine your tires for any signs of excessive or abnormal tread wear, punctures or other signs of physical damage. Any cuts, abrasions or other blemishes or defects anywhere on the tire should be examined by a trained service technician or tire professional right away.

“As a tire wears, there are also these things called ‘wear bars’ located at any number of points on the tire that tell you that your tire has 2/32 of an inch or less of tread left,” says Zielinski. “And if you see these on a tire, they are a visible indicator that you need to replace the tire. Replacing your tires when you can see all of Abraham Lincoln’s head using the time-honored ‘penny test’ is also a good rule of thumb.”

And now that spring is here — the rainy season across much of the country — it’s not good to be driving on tires that have insufficient tread.

“We’ve actually become big proponents of upgrading the time-tested ‘penny test’ to the ‘quarter test’ — using George Washington’s head in the same fashion that we once used Lincoln’s on the penny,” says Edmonds. “If you can insert a quarter into your tire’s tread and see George Washington’s entire head, well, you’re just below 4/32 of an inch versus 2/32 of an inch for a penny. But that small difference in terms of remaining tread can be tremendous in terms of a car’s stopping distance in wet weather.”

When you drive on a wet road on tires that have 2/32 of an inch of tread versus 4/32 of an inch of tread, worn-out tires can move much less water from the tire’s contact surface with the pavement, says Edmonds. “In a panic stop from 70 miles an hour — not an uncommon emergency maneuver on the highway — that difference in tread translates into an additional 100 feet of stopping distance.”

“At present there really are no real hard-and-fast recommendations about tires in terms of their age,” says Zielinski. “Some automakers recommend replacing a tire after six years while others recommend replacing a tire after 10 years of service — but as yet there is really no data indicating that a tire of a certain age is going to be unable to perform.”

“Our experience has been that, when properly cared for, most street tires have a useful life of between six to 10 years,” says Edmonds.

But if you think that tire dressings can make your tires last longer, guess again.

“There are currently one or two new products out there that are actually beneficial for your tires,” says Zielinski. “But, generally speaking, tire-dressing products should not be used because by bringing out that nice, wet, black shine that everybody is so interested in today, you could actually be pulling out certain chemical properties from the tire which the tire needs during its life. So you can effectively wind up bringing out important antioxidants that otherwise protect your tire from the elements. The best thing that you can do is just to wash your tire with regular soap and water.”

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