Top five tire myths

Most of us know very little about tires – and a lot of what we think we know is flat wrong. Here are five commonly held myths about tires.

Here's the truth: An all-season tire trades wet-road traction (among other things) for enhanced mobility in snow and in subfreezing temperatures. Designing a tire is an exercise in compromises: Improving a certain performance factor almost always means diminishing one or more other performance factors. (Some more accurately use the term "three-season" when referring to summer tires.)

To make things even more complex, when you switch categories (or even brands), the results may change. An ultra-high-performance all-season tire may offer better wet-grip than a high-performance summer tire or a grand-touring summer tire.

Here’s the truth: Many are surprised that tires can reach the end of their lives without having gone far or done much work.

Some auto manufacturers recommend replacing tires every five or six years, regardless of tread depth. A tire that's been on a car seven or eight years is much like a 65-year-old human: No matter how fit and healthy he looks, he shouldn't play football against 19-year-olds. If it's 105 degrees outside, a simple stroll can be deadly to both out-of-shape older people and poorly maintained old tires.

Here's how you can tell how old your tire is:

• Look on the sidewall to find the letters "DOT." Following that will be a sequence of numbers, which may be in three or four separate windows. The last four numbers tell when the tire was made: "3112" means the tire was built during the 31st week of 2012.
• Check for hairline cracks in the sidewall. Cracks are a strong indication the tire needs to be replaced.
• Inspect for deteriorating rubber, which can be a big problem for rarely driven vehicles, such as motor homes, collector cars, exotic cars, vehicles owned by senior citizens and vans operated by charitable organizations.

Here’s the truth: A new quality tire will not burst even if the "max press" is exceeded by a very large amount. However, all bets are off if the tire has been damaged or it's fitted on a cheap or damaged wheel.

The “max press” number, coupled with the “max load” number (also found on the sidewall), provides the maximum load-carrying ability of a tire. Know this: It's air pressure that allows the tire to carry a load. At 1 pound per square inch (psi) of air pressure a tire can support no weight. To increase its load-carrying capacity, air pressure must be increased. (Imagine a plastic soft-drink bottle: With the top off, it's easily crushed; but when it’s new and unopened, it can support a grown man.) However, at some pressure, adding more air to the tire will not provide increased weight-carrying capacity. That's what the "max load/max pressure" means.

Here’s the truth: The proper inflation pressure for a tire is determined by the vehicle manufacturer – not by the tire manufacturer. The government now requires new cars to have that recommended pressure on a placard located on the driver's doorjamb. On older cars this placard was often on the doorjamb, but it could also be found on the trunk lid, glove box door, console lid or fuel door. If you can't find the recommended pressure placard, look in your owner's manual or call your vehicle manufacturer's customer service department. Inflating the tire above the vehicle manufacturer's recommendation may make it more susceptible to damage from potholes and will reduce ride comfort.

Here’s the truth: As with most products, you get what you pay for.

It's easy to see how this misconception developed. Each tire company has a premium brand upon which it focuses its research, development and testing. In addition, almost all of these companies produce other brands. Many build tires for others – such as auto-parts stores – to sell under the store's brand. As you progress down this list, development and testing quickly drop to no more than legal requirements. The R&D from the premium brand often – but not always – trickles down into the budget brands. So maybe the difference is so small that you can't tell the difference. Or maybe not.

You can be fairly certain that discount and private brand tires built by big-name companies will resist failures as well as that company's premium offerings. After all, if the store-brand tire fails, that tire company gets sued just as if the tire boasted a premium brand name. However, things like tread life, traction, ability to resist deep water, noise and comfort will probably – but not always – be inferior.

It's easy to argue that tires are the most complex, most important, least understood, least appreciated and least maintained component on any vehicle. Serious drivers will tell you they know that already.