When did they start using TPMS sensors?

Oct. 21, 2024

Tire-pressure Monitoring Systems: A Comprehensive Overview

Understanding Electronic Systems in Vehicles

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A tire-pressure monitoring system (TPMS) is designed to keep an eye on the air pressure within vehicle tires. When installed, TPMS provides real-time information about tire pressure to drivers, delivering data through a gauge, a pictogram display, or a simple warning light. Generally, TPMS can be categorized into two main types: direct (dTPMS) and indirect (iTPMS).

TPMS can be either integrated into vehicles during manufacturing or added as an aftermarket feature. The primary aim of a TPMS is to help prevent traffic accidents, enhance fuel efficiency, and reduce tire wear caused by under-inflated tires by identifying hazardous tire conditions promptly. The implementation of this technology made its debut in luxury vehicles in Europe during the late 1980s and early 1990s, gaining momentum in the United States after the passing of the TREAD Act, which was a response to the Firestone and Ford tire controversy.

As we moved into the 21st century, TPMS mandates proliferated in various countries including Russia, the EU, Japan, South Korea, and many others in Asia. Specifically, beginning in November 2014, TPMS became mandatory for new vehicles within the European Union. However, a survey carried out before this date reported that between November 2014 and August 2015, approximately 54% of passenger cars in countries like Sweden, Germany, and Spain lacked TPMS—an estimate thought to be low.

Additionally, aftermarket valve cap-based dTPMS systems have emerged, requiring a smartphone, app, or a portable display for use on bicycles, cars, and trailers.

The Evolution of TPMS

Early Adoption of TPMS

Recognizing the importance of tire pressure on vehicle safety and operational efficiency, the European market began adopting tire pressure monitoring (TPM) as an optional feature for luxury passenger vehicles starting in the 1980s. The first passenger car to feature TPM was the Porsche 959, launched in 1986, which utilized a hollow spoke wheel system created by PSK. In 1996, Renault implemented the Michelin PAX system for its Scenic model, followed by PSA Peugeot Citroën making TPM a standard feature on the Peugeot 607. In 2001, Renault rolled out the Laguna II, notably the first mass-produced mid-sized passenger vehicle to include TPM as standard.

In the United States, General Motors introduced TPM for the Corvette in 2001, which was coupled with Goodyear run-flat tires. This system employed sensors in the wheels, providing drivers with real-time tire pressure data for each tire as well as alerts for both over-inflation and under-inflation conditions. It has been included as a standard trait of Corvettes since its introduction.

The late 1990s Firestone tire recall incident, linked to over 100 fatalities due to tire-related rollovers, led Congress to respond with the TREAD Act. This law required the implementation of reliable TPMS technology in light motor vehicles under 10,000 lbs to alert drivers about under-inflation issues effectively. This legislation applied to all light motor vehicles sold after September 1, 2007, with a gradual implementation across various model years.

Subsequent international moves included obligations for South Korea and Japan to adopt similar TPMS mandates around the same timeframe, signifying a global recognition of the benefits of tire pressure monitoring.

Run-flat Tire Technology

The introduction of run-flat tires has prompted manufacturers to incorporate basic TPMS systems that are mandatory when utilizing such tires. Unlike standard tires, a driver may not notice a flat tire when it is run-flat, leading to the development of "run-flat warning systems." Typically, initial iterations of these systems are based on indirect methods, ensuring that vehicles don't travel beyond the set limits when using run-flat tires.

Comparing Direct and Indirect TPMS

Understanding Indirect TPMS

Indirect TPMS (iTPMS) does not rely on physical pressure sensors. Rather, it estimates and monitors tire pressures through software by integrating existing sensor data such as wheel speeds, acceleration, and driveline dynamics. The first-generation iTPMS functions by detecting that under-inflated tires have a slightly smaller diameter compared to properly inflated ones, leading to a higher angular velocity that can be measured through wheel speed sensors utilized in ABS and ESC systems.

Though iTPMS systems can detect under-inflation in multiple wheels simultaneously through advanced signal processing techniques, they cannot provide absolute pressure readings and thus require a reset after manual wheel servicing.

Direct TPMS Explained

Direct TPMS (dTPMS) employs hardware sensors mounted inside the wheel, typically on the valve itself. These sensors measure tire pressure directly and relay that information to the vehicle's onboard computer system. Many products and systems can display real-time tire pressure data for each wheel, providing precise monitoring capabilities even when the vehicle is stationary.

Although dTPMS systems can vary in technology and data transmission methods, they face challenges like environmental exposure and battery constraints. Some sensors even utilize wireless power systems to extend battery life and enhance data transmission frequency, addressing some limitations faced in performance-heavy scenarios.

Maintenance Considerations for TPMS

Corrosion of Valve Stems

The first-generation TPMS integrated onto the valve stems can experience corrosion issues. When metallic valve caps corrode and fuse with their stems, efforts to detach the caps can damage the stem, rendering the sensor ineffective. Caution is needed when replacing valve cores, as using the wrong types may also lead to similar problems.

Compatibility with Tire Sealants

Concerns about tire sealants' compatibility with dTPMS sensors have arisen, as they may interfere with the sensor functioning if they come into contact. While some sealant manufacturers claim compatibility, there are still risks that may void TPMS warranties.

Key Benefits of TPMS

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Maintaining correct tire pressure is crucial for vehicle safety, impacting key factors such as braking distance and lateral stability. Research from GITI estimates that a 10% under-inflation can lead to a 1% drop in fuel economy, causing significant fuel waste, particularly in the United States. Under-inflated tires contribute to structural failures, safety issues, and environmental pollution due to increased emissions. Key advantages of TPMS technology manifest in improved fuel efficiency, extended tire longevity, enhanced safety, and reduced environmental impact.

Privacy Implications of Direct TPMS

The unique identifiers transmitted by each tire potentially pose privacy concerns, as they enable easy tracking of vehicles using sensors along roadways. Although encryption of communications could alleviate these issues, no such provision has been mandated by authorities yet.

Considerations for Heavy-duty Vehicles

Current regulations mainly apply to light motor vehicles under 10,000 lbs. For heavier vehicles, distinctive systems and technologies are in development to replace standard TPMS implementations.

Global Mandates for TPMS

United States Regulations

The United States was the pioneer in mandating TPMS following a series of traffic accidents attributed to low tire pressure. Enacted in the early 2000s, FMVSS 138 requires all new passenger vehicles to be equipped with TPMS, to provide alerts for significant under-inflation, enhancing overall safety.

South Korean Regulations

Following a gradual approach, South Korea made TPMS compulsory for vehicles under 3.5 tons. Eventually, all vehicles manufactured in the region must now include this safety feature.

Identifying TPMS Icons

Common dashboard icons for TPMS include indicators for low tire pressure and system failures.