Wednesday, July 6, 2005

Car Culture

Underinflated tires cut fuel economy, shorten tread life

By John McCormick / Special to The Detroit News

Even if you are not an auto racing enthusiast, you might have heard about the recent Formula One race in Indianapolis that turned into a farce after all but three teams withdrew because of concerns over the safety of their tires.

The incident underscored a fact that's worth repeating: whether you're doing 200 mph on a racetrack or heading to the grocery store in your minivan, make sure your tires are in good condition and properly inflated.

Simple though these maintenance recommendations may sound, they are often the cause of confusion for consumers and regularly ignored. Even auto companies, tire makers and the government have a hard time agreeing on the right way to keep us running on decent, correctly inflated tires.

Ford Motor Co. and DaimlerChrysler AG's Chrysler Group recently began advising U.S. customers to replace their tires after six years. The automakers say the tires should be changed regardless of their condition because they degrade over time.

However, tire makers are disputing this recommendation, saying that proper tire maintenance plays a major role in the life of rubber.

A related argument is being played out in court over a government requirement for tire pressure monitors to be mandatory in future vehicles. Detractors say the devices, as specified by the authorities, are inaccurate.

What's the consumer to make of this rash of conflicting claims and information? In my experience, it's tough enough to keep track of a vehicle's tire pressure, even when one does remember to check regularly.

That's because few gas stations these days seem to care about providing decent air pumps. When you do find a station with an air hose, it's often in bad shape and lacking a working pressure gauge.

One answer to the missing gauge problem is to purchase your own quality unit -- the latest digital ones are inexpensive, simple to use and accurate. Make sure you keep it handy and visible inside your vehicle, if for no other reason than to remind you to monitor your tires, hopefully on a regular basis.

Ideally, remember to check your tires before you drive your vehicle more than a few miles, because the recommended inflation pressures are for cold tires.

If you set your pressures when the tires are hot, they will be underinflated when cold or, more importantly, when the air temperature drops significantly -- think wintertime.

And underinflated tires can be a serious liability. Being low by as little as 6 pounds (per square inch) will reduce the tire's tread life by as much as 25 percent and could lead to tire failure.

Low pressures will also impair your vehicle's handling and road holding characteristics.

Last but far from least, running on underinflated tires can worsen your fuel economy by as much as 5 percent, something to consider in this world of high gas prices.

John McCormick is a columnist for The Detroit News' Autos Insider Web site. He can be reached at jmccormick@ detnews.com.