AP NEWS

TIRE TUNE-UPS

September 22, 2018

Automotive trends and consumer behavior ebb and flow, but when it comes to the vehicle fundamentals of stop and go, tires are critical. Don’t let looks fool you: though they may still be as “round and black” as tires were in the 1980s, modern tires are incredibly advanced.

Thanks to engineering and manufacturing that relies on everything from chemistry and finite element modeling to botany, today’s tires have several tricks up their sleeves. Some are designed to operate safely despite nail punctures while others incorporate tread designs that not only are tailored to certain kinds of weather and road surfaces, they may morph as the tires wear, revealing different tire compounds or patterns.

For example, Bridgestone’s Ecopia H/L 422, the newest addition to the Ecopia low-rolling resistance tire line can not only be fitted to vehicles that weren’t originally equipped with fuel-saving tires, the manufacturer said it delivers improved braking in the wet and is backed by a 70,000-mile limited treadwear warranty. Strides have also been made in run-flat tires. Bridgestone’s DriveGuard run-flats ride better, are priced competitively and are available for vehicles that weren’t originally equipped with run-flats.

You could say tires are the great equalizer. Whether you drive a Ford F-250, a Porsche 911 or a Kia Rio, inflating your knowledge of tires could save you a lot of money — or even your life.

Existing tires

The first step to getting the safety, longevity, performance and comfort out of the tires already on your vehicle is to open the driver’s door. On the door jamb, usually mounted vertically, you’ll find a sticker — sometimes referred to as a placard — with essential tire information such as the manufacturer’s specified tire size and inflation pressure for the front, rear and spare tires.

Be sure to check or adjust the tires’ inflation when the tires haven’t been driven for several hours. And if the vehicle has one, don’t forget to air the spare. The specified pressure will often be higher unless you’re lucky (or smart) enough to have car with a full-size, matching tire.

A common error is inflating tires to the maximum recommended inflation pressure indicated on the tires’ sidewalls. There could be harsh consequences since today’s SUV and pickup tires can max out at 50 pounds per square inch (psi) — or even 80 psi for light-truck (LT) tires.

This potential pitfall was driven home earlier this year when a Nissan Titan Pro-4X we were evaluating rode very stiffly, even for a truck built for off-road use. We cycled through the driver’s information screens, and, thanks to the trucks tire pressure monitoring system that indicates each tire’s inflation pressure, we were able to quickly spot the culprit: all four LT275/65R18 tires were indicating 81 to 83 psi.

Over-inflation can also be rough on your pocketbook by causing the tire’s center tread to wear prematurely. Replacing tires sooner than you normally have to can be an expensive proposition since a set of tires for a truck, SUV, sports car or high-end sedan can easily run $1,000 or more before mounting and balancing.

Keeping up with tire rotations will save money in the long run. Tire makers, retailers and auto manufacturers recommend tires be rotated about every 3,000 to 5,000 miles, even if the tread appears to be wearing normally.

Another hazard of driving on unevenly worn tires (or new tires and old tires on the same vehicle) is that some all-wheel-drive systems can be damaged since a used tire will have a smaller circumference than one that’s not as worn.

But remember that some vehicles — such as sports cars — use directional or asymmetrical tires, or wider wheels and tires at the rear than the front, which can kill any chance of normal rotations. Cha-ching!

And let us not forget rental cars. Examine the tires before accepting the vehicle. If the tires are worn, it could indicate suspension problems or degraded handling and braking. I rejected the first rental car offered to me on a Hawaiian vacation because of the sketchy condition of its tires.

While the traditional standard to replace tires has been when the tread depth reaches 2/32nds of an inch, that may be too risky, said

the AAA. Together with the Automobile Club of Southern California’s Automotive Research Center, the AAA tested all-season tires and found that even with 4/32-inch of rubber, a car’s stopping distance, on average, increased by 87 feet, while a light truck needed 86 more feet to stop, compared to new tires.

“Even the most advanced safety systems rely on a tire’s basic ability to maintain traction, and AAA’s testing shows that wear has a significant impact on how quickly a vehicle can come to a stop in wet conditions to avoid a crash,” said John Nielsen, head of AAA’s Automotive Engineering and Repair. On average, cars with the 4/32-in. of tread also showed a 33 percent reduction in handling while the light trucks’ handling ability degraded by 28 percent.

Replacement tires

If it’s time for fresh tires, make sure you do your homework, starting with that tire information placard stuck to the door jamb.

Selecting the right tire is essential. There are all-season tires (“three-season” would be the more accurate term if you encounter heavy snow and ice), light truck/SUV tires, run-flats and dedicated winter/snow tires that are all further classified with descriptors like touring, ground touring, high-performance, ultra-high performance, all-terrain and summer performance.

If you’re happy with the tires that came on your vehicle, you can start with the same manufacturer, model and size of the original tires. But many may not realize that won’t necessarily get you the exact tires were installed on your car at the factory. Automakers have their own priorities. Low-rolling resistance, for example, is a big deal because tires affect EPA fuel economy ratings. Replacement tires of the same make, model and size can also differ slightly to meet Mercedes-Benz, BMW or Porsche requirements.

Meanwhile, getting the correct tire for a specific application is made easier for General Motors vehicles thanks to a unique “tire performance criteria” (TPC) number that goes on the sidewall of the tire along with the usual width, rim diameter, aspect ratio, speed and load ratings.

Many car dealerships have jumped into selling tires, figuring that their service departments can serve as a one-stop shop and add to customer convenience.

Where once 14- and 15-inch tires were common, tires ranging in diameter from 16- to 22 inches dominate today’s passenger car and light truck landscape. The wider, low-profile tires look great and can improve traction and response — but not without a price.

Tires are designed to support the weight of the vehicle. The more air capacity a tire has, the more weight the tire can support. This is particularly important with trucks and SUVs. Although upsizing from stock diameter to 20- and 22-inch wheels may be popular, custom wheels and tires may require recalibration of the tire pressure monitoring system. The lower profile tires also have less space for the air that supports the vehicle and they’re vulnerable to damage from curbs and potholes.

The problem is so prevalent that some dealerships offer optional insurance against tire and wheel damage when you buy a new car, truck or SUV.

Mixing tire sizes, tread designs or types can be dangerous. If you’re only replacing one or two tires, put the new tires on the rear, even if the vehicle has front-wheel-drive. The new rubber and its deeper grooves will have less of a tendency to hydroplane (slide on a thin layer of water) that could cause the vehicle to skid out of control.

With many young people now off at college out of town or out of state, parents should stress the importance of tires. We knew of one student who drove from Dallas to Houston one summer not knowing that one of her tires was down to 9 psi. (It was an older vehicle that didn’t have a tire pressure monitoring system.) Fortunately, the tire didn’t blow but too much heat never does tires any good.

“Overloading a properly inflated tire or underinflating a properly loaded tire have similar effects in that they both cause the tire to deflect more than designed and generate excessive internal stress and strain, as well as heat,” said Keith Willcome, an engineer with Bridgestone Americas Tire Operations. “Excessive heat further aggravates the effects of overloading/underinflation because it negatively affects the ability of the rubber to manage the stress and strain as it goes through a deflection cycle.”

For more on tires and tire care, see tiresafety.com or ustires.org/safety. After digesting that info, I’ll bet you’ll come to realize you’re buying a set of tires as much as you’re getting a new car.

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