Nine months ago, the National Highway Traffic Safety Administration (NHTSA) was forced to vacate its 2002 tire pressure monitoring system rule after it was thrown out by a United States appellate court. Where does the issue stand?
A NHTSA spokesman says it took the court's decision to heart in crafting a new proposed standard. "We've written a notice of proposed rulemaking to reinstate the tire pressure monitoring system (TPMS) device rule. It is under review, and we expect to publish it this fall."
The point of contention between NHTSA and the U.S. Court of Appeals for the Second Circuit in New York was the use of indirect tire pressure monitoring systems. In its original resolution, NHTSA said either direct or indirect systems were fine; the court said direct systems were the only way to go. So it is believed the new rule will favor direct systems.
In addition, under the old rule, tire pressure monitors had to warn drivers when tire pressure fell at least 25% below the vehicle manufacturer's recommended psi level. The Rubber Manufacturers Association (RMA), among others, thinks those standards are too broad to be effective.
"The trigger point for a tire pressure monitoring system to warn a driver must be when the tire is overloaded for its inflation pressure," says Donald Shea, CEO and president of RMA.
Will NHTSA revise the psi limits? "All the details will be in the proposed notice," was all NHTSA would say.
Direct vs. indirect
There are -- or were -- two generally accepted types of tire pressure monitoring systems.
1. Direct.. Each wheel is fitted with a sensor that transmits tire pressure readings to, in most cases, a dashboard display. The court prefers this TPMS because the transmissions are not only continuous -- and, therefore, timely -- but also tire-specific.
2. Indirect. Antilock brake sensors are designed to detect low tire pressure by measuring differences in rotational speed at the four wheel positions. However, they don't immediately let the driver know about low-pressure situations, or which tire (or tires) is low. Also, critics complain that high speeds and varying surfaces can affect the readings.
The Office of Management and Budget and the Bush administration swayed NHTSA to include indirect systems in its ruling in the hopes of attaining cost savings and promoting ABS.
The players
The race among enterprising companies and tire manufacturers to develop an acceptable direct TPMS for light vehicles starts with the sensor makers. Some are fairly new to the game, like Infineon Technologies AG. Other low-pressure monitoring sensor makers include GE Industrial Systems, Texas Instruments Inc., Delphi Corp., Motorola Inc. and Fujikura Ltd. (a supplier to Goodyear Tire & Rubber Co.).
Some systems rely on batteries. However, the big focus is on the battery-less transmitter.
The TPMS players, tiremakers included, are original equipment oriented. They are (listed alphabetically) as follows:
* Advantage PressurePro LLC. The PressurePro system utilizes sensors that screw onto the valve stem. They read pressures from 10 to 150 psi on one to 34 wheel positions, and visually and audibly alert drivers to low pressure situations.
* ALPS Electric Co. Ltd. Instead of battery-powered transmitters, battery-less transponders send information back and forth to a central transceiver. The company says it also "will be working with the world's leading tire and valve manufacturers to design a system that automobile manufacturers can easily incorporate into new cars."
* Atmel Corp. The company has available a new UHF ASK/FSK transmitter IC optimized for use in battery-powered modules that monitor tire-pressure systems. The ATA5756 is designed for North American applications in the 315-MHz range.
The new TPMS IC helps to drastically reduce total current consumption, thus extending the modules' life, says the company.
Eaton Corp. The Eaton Tire Monitor System combines radio-frequency technology and tire pressure sensors to alert truck operators of a loss of tire pressure. It features Schrader-Bridgeport sensors.
Goodyear. Software developed by Goodyear and Siemens VDO Automotive Corp. can calculate recommended inflation pressure based on factors like ambient temperature, tire load, speed of vehicle and driving habits. Psi threshold levels can be adjusted.
The companies call the software "the first step toward the next generation of tire pressure monitoring systems, which will be battery-less and tire-embedded as part of the total Siemens VDO/Goodyear Low Pressure Monitoring System targeted for auto makers." They also are making the software available to other companies.
* Groupe Michelin. Its EnTire Solution tire pressure monitoring systems, developed in partnership with TRW Inc., feature sensors mounted on the valve stem inside the wheel. The "advanced" system warns the driver when pressure is getting too low, as in a slow leak.
The joint venture is supplying OE fitments to Honda Motor Co. Ltd. (2004 Acura MDX), Fiat SpA, Hyundai Motor Co. and Kia Motors Corp.
TRW and Michelin also are developing advanced sensor-transmitters with valve mount and off-valve mount options compatible with Michelin's PAX run-flat system. "These two mounting options offer OEMs worldwide more flexibility in selecting a TPM sensor-transmitter for use with conventional and run-flat tire systems," says Alain Charlois, director of business development for TRW Automotive Electronic's Safety and Security division.
Johnson Controls Inc. The company's PSI tire pressure monitoring system is designed for both standard radial tires and run-flats. The company says tire pressure information is accurate within one pound per square inch.
* Logistics Pacific Corp. The battery-powered transmitter can be mounted inside the tire or the valve cap. It has up to a five-year battery life.
Nokian Tyres plc. Nokian's wireless TPMS systems can transmit real-time data on tire pressures and temperatures to key-chain receivers and mobile phones. Designed for aftermarket use, the Roadsnoop system also is available in a hard-wire version for vehicles that run all day, like police cars and taxis.
Pirelli & Cie SpA. The X-Pressure "safety system" has low-powered sensors that adhere directly to the inner surface of the tire and function even when the vehicle is at a standstill. According to Pirelli, they can be removed and re-installed on new tires (for OE applications, Pirelli says it might be able to cure the sensor directly into the tire).
The X-Pressure TPMS does not connect to the car's battery.
* Schrader Electronics Ltd. Its radio frequency-based remote tire pressure monitoring system, SmartValve, features electronic sensors attached to the tire valves to transmit pressure data. The company says it is supplying OE manufacturers.
* SmarTire Systems Inc. Tire pressure and temperature information is transmitted wirelessly from the sensor in the wheel to the display unit. The digital display shows both tire pressure and temperature data. A warning alert is triggered if a tire's pressure drops or if a tire's temperature rises beyond a preset threshold limit.
The Canadian company recently signed a distribution agreement with Lexani Wheel Corp. to include SmarTire TPMS on Johnson brand wheels.
There have been direct tire pressure monitoring systems for the commercial market for years. Yokohama Rubber Co. Ltd.'s HiTES (Hi-Technology Tire Engineering System) is designed to measure and control air pressure and internal temperatures in bus and truck tires. Meritor Automotive Inc. and Pressure Systems International Inc. jointly market automatic tire inflation systems for trailer applications.
CrossLink Inc.'s TireBoss system is a wireless link from small radio frequency tags mounted in each tire to fleet operators via the Web. "Our hope is to go and build a multi-channel strategy targeted mainly at enterprise fleets," says Richard Booth, vice president of sales and marketing for CrossLink. "We would like to bring the product to the tire manufacturing industry."
Until then, we wait
From a practical standpoint, when tire pressure is not sufficient to carry the proper load, tread life suffers. Under-inflation negatively impacts a vehicle's fuel consumption as well.
According to a 2001 NHTSA survey, 14% of all passenger car and light truck owners check the air pressure in their tires. A 2003 RMA motorist survey similarly concluded that only a small percentage of drivers correctly check their tires.
So the need for tire pressure monitoring systems is there. Also, as part of its final tire testing ruling announced last June, NHTSA already has adopted a low inflation pressure test that will "ensure a minimum level of inflation at which tire pressure monitoring systems will be required to be activated."
It may not be clear what the content of the new proposed TPMS ruling will be. One thing is certain, however: Widespread use of tire pressure monitoring systems is inevitable. NHTSA's focus on safety, courtesy of the TREAD (Transportation Recall Enhancement, Accountability and Documentation) Act, will see to that.
And it will happen sooner rather than later. Before the courts struck it down, NHTSA's original rule mandated TPMS technology in all domestic cars and light trucks after the 2003 model year.
When will tire pressure monitoring systems become standard equipment on passenger cars and light trucks? The countdown begins again this fall.
Literally on the cutting edge: My personal experience with one TPMS
In November of 2002, I met with the president of Algonquin Scientific, the company manufacturing and marketing the TireSafe low pressure monitoring system. I volunteered to have the system, consisting of four small sensors and receivers, a display module and interconnecting wires, on my Dodge Neon.
The sensors were mounted on the wheels, while the receivers were mounted in the adjoining wheel wells.
Eventually, one of the receivers came loose and cut the inside of the tire. I had it removed, and since the tires were worn, purchased four new ones. (Algonquin Scientific offered to pay for the tires a year later.)
I still have the owner's manual: "As the owner of the TireSafe LPM you will enjoy the security and convenience of monitoring the tire pressure in your vehicle while you are driving."
That didn't always happen. Maybe it was a short circuit or bad connection, but the lights on the display module attached to my steering column didn't flash when they were supposed to.
"This market isn't going to take off for 12 months," President Michael Landers told me at SEMA. At the time, he was counting on the NHTSA's original TPMS mandate. That ruling fell through, and so, it seems, has TireSafe. -- Bob Ulrich
