The History of TPMS Lights - Inertion

One of the most perilous situations encountered by drivers is low tire pressure, a critical issue that is often easily overlooked and requires minimal effort to fix. For many years, vehicles did not come equipped with the advanced tire pressure warning systems we have today. A study conducted by Indiana State University in the 1990s found that 1.5% of all motor vehicle accidents were attributed to under-inflated tires. Unfortunately, during that time, technology did not yet exist to provide affordable solutions for this issue.

The passage of the TREAD Act by the US government

In the late 1990s, a series of serious rollover accidents involving Ford Explorer SUVs fitted with Firestone tires highlighted the dangers of under-inflated tires. These incidents led to over 3,000 injuries and about 250 fatalities. The widespread recall of Firestone tires in response to these events prompted the US government to enact the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act during the Clinton administration in 2000. As part of this legislative measure, it became mandatory for vehicles sold in the United States to have a Tire Pressure Monitoring System (TPMS) that alerts drivers when one or more tires are underinflated by 25% or more.

There are two primary types of TPMS: direct and indirect systems. Despite using different methods, both systems serve the same purpose: to illuminate a warning light on the vehicle's dashboard whenever a tire is identified as under-inflated. Typical TPMS warning lights appear as a horseshoe shape with an exclamation point in the center, resembling a tire's cross-section.

Understanding Indirect TPMS

Unlike a traditional tire gauge, an indirect TPMS does not directly measure tire pressure. Instead, it uses wheel speed sensors typically found in anti-lock brake systems. These sensors track the rotation speed of each wheel, and the onboard computer system compares the revolutions of each tire to the overall speed of the vehicle. When the computer detects that one tire is spinning faster than it should be, indicating a potential under-inflation situation, the TPMS light is activated.

Advantages and Disadvantages of Indirect TPMS

Though indirect monitoring systems are often less costly than their direct counterparts and require less programming and maintenance, they come with their own set of challenges. For instance, if a driver installs new tires that differ in size from the originals, the system can become inaccurate, as it calculates tire size based on revolution rates. Additionally, if tires wear unevenly, the system may fail to provide an accurate assessment. It’s important to note that indirect systems must be reset after every tire inflation and rotation.

The Advantages of Direct TPMS

On the other hand, a direct TPMS utilizes sensors in each tire to monitor both pressure and, in some cases, temperature. This information is wirelessly transmitted to a central control module for analysis. If tire pressure is low, the warning light on the dashboard will turn on. Direct systems are generally more accurate than indirect systems and do not require resetting after tire rotations or inflations, although they tend to be more expensive.

The Dangers of Driving with Under-Inflated Tires

Regardless of the type of TPMS your vehicle employs, recognizing and acting upon the low tire pressure warning can dramatically reduce the chances of accidents related to under-inflated tires. Driving on such tires is extremely hazardous, and fortunately, modern technology spares drivers the ordeal of performing manual inspections with a tire gauge before each trip.

Improving Tire Pressure Maintenance with Nitrogen

In addition to TPMS, using nitrogen to inflate tires can offer an extra layer of safety and convenience. Research indicates that nitrogen-filled tires maintain their pressure longer compared to those filled with conventional air.