Nothing but compressed air, certainly not the rubber tread on the tires, keeps your vehicle suspended over the road.
So, the amount of air in the tires is vitally important, a fact that is relentlessly driven home by safety experts but ignored by many motorists.
After more than 80 people died in Ford Explorers that were equipped with poorly inflated Firestone tires in the late 1990s, Congress passed the Tread Act, mandating, among other things, that auto makers install tire pressure monitoring systems on future vehicles. Currently being phased in, the act will require all new cars to have such a monitor by September 2008.
But as implemented by the National Highway Traffic Safety Administration, the rules were quickly assailed by critics for a weak and ineffective approach to the problem.
Since 2000, the issue of tire pressure has become even more critical, as motorists opt in increasing numbers for low aspect ratio tires that depend on closely monitored air pressure to avoid blowouts caused by potholes and other road hazards.
A close look at tire pressure monitoring systems shows that, in general, they will fail to relieve car owners of the burden of closely watching their tire pressures. While they may help to alert people of dangerously low air pressure, they will generally not warn drivers of air pressure low enough to cause slow tire damage.
Two basic types of technology are used in tire pressure monitoring systems, or TPMS: direct and indirect. The less expensive approach adopted by some auto manufacturers is called "indirect" and uses anti-lock braking systems to provide signals for the system.
When a tire has low pressure, it tends to rotate at a slower speed than the other tires, which the anti-lock system sensors and computers can detect. All auto makers have to do is create some software and put a warning light on the dashboard.
But Clarence Ditlow, executive director of the Center for Auto Safety, said these systems "are wrong 50% of the time." Ditlow, along with the Washington-based consumer group PublicCitizen, sued the NHTSA and won a judgment that the agency's rule did not satisfy the intent of the Tread Act. But ultimately, the agency issued a rule that still left safety advocates and some members of the tire industry fuming.
