Don't TREAD on Me
by Matt LaDuke

As a result of the Transportation Recall Enhancement, Accountability, and Documentation (TREAD) Act, the U.S. National Highway Traffic Safety Administration (NHTSA) recently established a new Federal Motor Vehicle Safety Standard that requires the installation of tire-pressure monitoring systems (TPMSs) to warn the driver when a tire is significantly underinflated. The standard applies to passenger cars, trucks, multipurpose passenger vehicles, and buses with a gross vehicle weight rating of 10,000 pounds or less, except those vehicles with dual wheels on an axle. Initial short-term compliance will be required by November 1, 2003, and long-term compliance will be required on November 1, 2006. (For the full text of this mandate, visit Federal Motor Vehicle Safety Standards; Tire Pressure Monitoring Systems; Controls and Displays.)

This mandate is giving rise to a new market of components for the vehicle. Included are many electronic and a mechanical solution to make our cars safer.

There are two basic methods to monitor tire pressure: direct and indirect. Through its testing, NHTSA found that systems that use sensors to measure tire pressure directly (pressure-sensor based systems) were better able to detect underinflation, had more consistent warning thresholds, and were quicker to provide underinflation warnings than the systems that infer tire pressure from monitoring wheel speeds (wheel-speed based systems). Training the systems presented at least some level of problem for both system types. Wheel-speed based systems were found to be easier to maintain since there are no battery-life concerns, and the sensors are not exposed to tire mounting and roadway hazards.

TRW Automotive can provide both direct and indirect types of tire-pressure monitoring systems. According to Doug Campbell, vice president, engineering, Occupant Safety Systems, "Indirect systems can be offered at minimal cost in the case of vehicles already equipped with four-wheel anti-lock braking systems (ABS), while direct-monitoring systems can communicate a range of accurate information to the driver through telematic readouts in higher end cars." TRW had first included indirect TPMS algorithms in its ABS production system for the 2001 Ford Windstar. TRW is also developing the "EnTire Solution," an advanced direct TPMS, in cooperation with Michelin. Benefits include accurate readouts, the ability to indicate exactly what tire is underinflated, front or rear, and can also warn the driver if there will be a low-pressure tire problem in the near future through the use of predictive algorithms.

Schrader Electronics also offers a direct TPMS, and according to a recent press release, the new Generation II Smart Valve^® remote tire-pressure monitoring system from Schrader Electronics is smarter than ever. The secret? Schrader Electronic's exclusive Auto Rotation technology. The technology automatically locates the correct wheel transmitter and continues to monitor tire pressure, even after a tire position has changed. The basic operation of the systems is by means of a valve sensor on each wheel that sends tire-pressure information to the nearest wheel-well detector, which then signals the central receiver. The central receiver collects pressure information and signals the on-board computer and instrument display, which can read and display the correct tire pressure even when the car is stationary. See the Schrader Electronics Smart Valve® RF Tire Pressure Monitoring System page for more details.

Another company that offers direct TPMS is Beru AG. Their TSS (Tire Safety System) consists of a system of wheel electronics with pressure and temperature sensors that monitor the air pressure in the tire and transmit the values via a high-frequency antenna to an electronic control unit. If the pressure is too low, or in the event of a sudden loss of pressure, the system warns the driver by way of a display on the control panel. The valve and the wheel electronics have been designed to fit virtually every known wheel-rim contour. See the Wheel electronics and control unit for the TSS tire pressure monitoring system article for a picture of the system.

There is a simpler option available on the market as well. This option is available to all consumers today for the low price of only $12.95 for a set of 4. This is the Accu-Pressure Safety Caps, from Miracle Group, Inc. This simple component uses a GYR rating system for a quick visual indication of your tires' status. The valve caps will be GREEN when the tire pressure is adequate—within four pounds of the rated PSI, YELLOW if the tires are approximately four pounds underinflated, and RED when they are approximately ten pounds or more underinflated. The accuracy is stated to be within 1 PSI. For more information, including a link to order these valves, click over to www.gs-27.com/accu_pressure.asp?source=ov.to to have a look at the Accu-Pressure Caps.

Companies producing TPMSs are not the only ones benefiting from this new standard. Gentex, a pioneer in the electrochromic (EC) autodimming mirror industry, has introduced a tire-pressure monitoring mirror. If a tire is underinflated, as detected by the mirrors, a display alerts the driver so the driver can take the appropriate action. The article on Tire-Pressure Monitoring Mirrors will give you all the details you need. In addition, Murata Electronics recently introduced the industry's smallest SAW Resonator. TPMS applications was one of the driving factors to develop the resonator that is 45 percent smaller in area, 30 percent smaller in volume, and half the weight of Murata's conventional products. More details, including frequencies, can be found in the announcement Murata Electronics Introduces Industry's Smallest SAW Resonator.

The NHTSA estimated that 6,585–10,635 injuries and 49–79 deaths could be prevented with tire-pressure monitoring systems. Another study showed that underinflated tires were a probable cause of 1.4 percent of all motor-vehicle crashes, or 260,000 crashes out 18.3 million crashes each year. So for the sake of your family and yourself, check you tire pressure, and keep your tires properly inflated.

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