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A tire-pressure monitoring system (TPMS) monitors the
air pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equival ...
inside the
pneumatic tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over which ...
s on vehicles. A TPMS reports real-time tire-pressure information to the driver, using either a gauge, a pictogram display, or a simple low-pressure warning light. TPMS can be divided into two different types – direct (dTPMS) and indirect (iTPMS). TPMS are installed either when the vehicle is made or after the vehicle is put to use. The goal of a TPMS is avoiding traffic accidents, poor fuel economy, and increased tire wear due to under-inflated tires through early recognition of a hazardous state of the tires. This functionality first appeared in
luxury vehicle A luxury car is a car that provides increased levels of comfort, equipment, amenities, quality, performance, and associated status compared to moderately priced cars. The term is subjective and reflects both the qualities of the car and the ...
s in Europe in the 1980s, while mass-market adoption followed the USA passing the 2000
TREAD Act The Transportation Recall Enhancement, Accountability and Documentation or TREAD Act () is a United States federal law enacted in the fall of 2000. This law intends to increase consumer safety through mandates assigned to the National Highway Traffi ...
after the
Firestone and Ford tire controversy The Firestone and Ford tire controversy of the 1990s saw hundreds of people die in automobile crashes caused by the failure of Firestone tires installed on light trucks made by Ford Motor Company. Unusually high failure rates of P235/75R15 ATX, ...
. Mandates for TPMS technology in new cars have continued to proliferate in the 21st century in Russia, the EU, Japan, South Korea and many other Asian countries. From November 2014 TPMS was mandatory for new vehicles in the European Union; in a survey carried out between November 2016 and August 2017, 54% of passenger cars in Sweden, Germany, and Spain were found not to have TPMS, a figure believed to be an under-estimate. Aftermarket
valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...
cap A cap is a flat headgear, usually with a visor. Caps have crowns that fit very close to the head. They made their first appearance as early as 3200 BC. Caps typically have a visor, or no brim at all. They are popular in casual and informal se ...
-based dTPMS systems, which require a
smartphone A smartphone is a portable computer device that combines mobile telephone and computing functions into one unit. They are distinguished from feature phones by their stronger hardware capabilities and extensive mobile operating systems, whic ...
and an app or portable display unit, are also available for bicycles, automobiles, and
trailers Trailer may refer to: a Transportation * Trailer (vehicle), an unpowered vehicle pulled by a powered vehicle ** Bicycle trailer, a wheeled frame for hitching to a bicycle to tow cargo or passengers ** Full-trailer ** Semi-trailer **Horse trailer ...
.


History


Initial adoption

Due to the influence tire pressure has on
vehicle safety Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design. ...
and efficiency, tire-pressure monitoring (TPM) was adopted by the European market as an optional feature for
luxury Luxury may refer to: * Luxury goods, an economic good or service for which demand increases more than proportionally as income rises *Luxury tax, tax on products not considered essential, such as expensive cars **Luxury tax (sports), surcharge pu ...
passenger vehicles in the 1980s. The first
passenger vehicle A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded as t ...
to adopt TPM was the
Porsche 959 The Porsche 959 is a sports car manufactured by German automobile manufacturer Porsche from 1986 to 1993, first as a Group B rally car and later as a road legal production car designed to satisfy FIA homologation regulations requiring at least 2 ...
in 1986, using a hollow spoke wheel system developed by PSK. In 1996 Renault used the
Michelin PAX system The Michelin PAX is an automobile run-flat tire system that utilizes a special type of rim and tire to allow temporary use of a wheel if its tire is punctured. The core of Michelin's PAX system is the semi-rigid ring installed onto the rim using sp ...
for the Scenic and in 1999
PSA Peugeot Citroën The PSA Group (), legally known as Peugeot S.A. (Peugeot Société Anonyme, trading as Groupe PSA; formerly known as PSA Peugeot Citroën from 1991 to 2016) was a French multinational automotive manufacturing company which produced automobiles ...
decided to adopt TPM as a standard feature on the
Peugeot 607 The Peugeot 607 is an executive car produced by the French manufacturer Peugeot from September 1999 to June 2010. The 607, along with the smaller 407, were superseded by the 508 in March 2011. History The 607 was launched in October 1999, to r ...
. The following year (2000),
Renault Groupe Renault ( , , , also known as the Renault Group in English; legally Renault S.A.) is a French multinational automobile manufacturer established in 1899. The company produces a range of cars and vans, and in the past has manufactured ...
launched the Laguna II, the first high volume mid-size passenger vehicle in the world to be equipped with TPM as a standard feature. In the United States, TPM was introduced by General Motors for the 1991 model year for the Corvette in conjunction with Goodyear
run-flat tire A run-flat tire/tyre is a pneumatic vehicle tire that is designed to resist the effects of deflation when punctured, and to allow the vehicle to continue to be driven at reduced speeds - under – and for limited distances – usually , dependin ...
s. The system uses sensors in the wheels and a driver display which can show tire pressure at any wheel, plus warnings for both high and low pressure. It has been standard on Corvettes ever since.


Firestone recall and legal mandates

The Firestone recall in the late 1990s (which was linked to more than 100 deaths from rollovers following tire tread-separation), pushed the
United States Congress The United States Congress is the legislature of the federal government of the United States. It is bicameral, composed of a lower body, the House of Representatives, and an upper body, the Senate. It meets in the U.S. Capitol in Washing ...
to legislate the
TREAD Act The Transportation Recall Enhancement, Accountability and Documentation or TREAD Act () is a United States federal law enacted in the fall of 2000. This law intends to increase consumer safety through mandates assigned to the National Highway Traffi ...
. The Act mandated the use of a suitable TPMS technology in all light motor vehicles (under ), to help alert drivers of under-inflation events. This act affects all light motor vehicles sold after September 1, 2007. Phase-in started in October 2005 at 20%, and reached 100% for models produced after September 2007. In the United States, as of 2008 and the European Union, as of November 1, 2012, all new passenger car models ( M1) released must be equipped with a TPMS. From November 1, 2014, all new passenger cars sold in the European Union must be equipped with a TPMS. For N1 vehicles, TPMS are not mandatory, but if a TPMS is fitted, it must comply with the regulation. On July 13, 2010, the South Korean Ministry of Land, Transport and Maritime Affairs announced a pending partial-revision to the Korea Motor Vehicle Safety Standards (KMVSS), specifying that "TPMS shall be installed to passenger vehicles and vehicles of GVW 3.5 tons or less, ... ffectiveon January 1, 2013 for new models and on June 30, 2014 for existing models". Japan is expected to adopt European Union legislation approximately one year after European Union implementation. Further countries to make TPMS mandatory include Russia, Indonesia, the Philippines, Israel, Malaysia and Turkey. After the TREAD Act was passed, many companies responded to the market opportunity by releasing TPMS products using battery-powered radio transmitter wheel modules.


Run-flat tires

The introduction of run-flat tires and emergency spare tires by several tire and vehicle manufacturers has motivated to make at least some basic TPMS mandatory when using run-flat tires. With run-flat tires, the driver will most likely not notice that a tire is running flat, hence the so-called "run-flat warning systems" were introduced. These are most often first generation, purely roll-radius based iTPMS, which ensure that run-flat tires are not used beyond their limitations, usually 80 km/h (50 mph) and 80 km (50 miles) driving distance. The iTPMS market has progressed as well. Indirect TPMS are able to detect under-inflation through combined use of roll radius and spectrum analysis and hence four-wheel monitoring has become feasible. With this breakthrough, meeting the legal requirements is possible also with iTPMS.


Direct versus indirect


Indirect TPMS

Indirect TPMS (iTPMS) systems do not use physical pressure sensors; they measure air pressures using software-based systems, which by evaluating and combining existing sensor signals such as wheel speeds, accelerometers, and driveline data to estimate and monitor the tire pressure without physical pressure sensors in the wheels. First-generation iTPMS systems are based on the principle that under-inflated tires have a slightly smaller diameter (and hence higher angular velocity) than a correctly inflated one. These differences are measurable through the wheel speed sensors of ABS/ESC systems. Second generation iTPMS can also detect simultaneous under-inflation in up to all four tires using spectrum analysis of individual wheels, which can be realized in software using advanced signal processing techniques. iTPMS systems are sometimes referred to by other names, such as ‘Deflation Detection System (DDS)’ ''(e.g. Ford)'' or ‘Deflation Warning System (DWS)’ ''(e.g. Honda)''. iTPMS cannot measure or display absolute pressure values; they are relative by nature and have to be reset by the driver once the tires are checked and all pressures adjusted correctly. The reset is normally done either by a physical button or in a menu of the on-board computer. iTPMS are, compared to dTPMS, more sensitive to the influences of different tires and external influences like road surfaces and driving speed or style. The reset procedure, followed by an automatic learning phase of typically 20 to 60 minutes of driving under which the iTPMS learns and stores the reference parameters before it becomes fully active, cancels out many, but not all of these. As iTPMS do not involve any additional hardware, spare parts, electronic/toxic waste, or service (beyond the regular reset), they are regarded as easy to handle and customer friendly. As mentioned however, the sensors must be reset every time changes are done to the tire setup, and some consumers do not wish to have this added responsibility. Since factory installation of TPMS became mandatory in November 2014 for all new passenger vehicles in the EU, various iTPMS have been type-approved according to UN Regulation R64. Examples for this are most of the VW group models, but also numerous Honda, Volvo, Opel, Ford, Mazda, PSA, FIAT and Renault models. iTPMS are quickly gaining market shares in the EU and are expected to become the dominating TPMS technology in the near future. iTPMS are regarded as less accurate by some due to their nature—given that simple ambient temperature variations can lead to pressure variations of the same magnitude as the legal detection thresholds— but many vehicle manufacturers and customers value the ease of use.


Direct TPMS

Direct TPMS (dTPMS) directly measures tire pressure using hardware sensors. In each wheel, most often on the inside of the valve, there is a battery-driven pressure sensor which transfers pressure information to a central control unit which reports it to the vehicle's onboard computer. Some units also measure and alert temperatures of the tire as well. These systems can identify under-inflation for each individual tire. Although the systems vary in transmitting options, many TPMS products (both OEM and aftermarket) can display realtime, individual tire pressures whether the vehicle is moving or parked. There are many different solutions, but all of them have to face the problems of exposure to hostile environments. The majority are powered by batteries which limit their useful life. Some sensors utilise a
wireless power system Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
similar to that used in RFID tag reading which solves the problem of limited battery life. This also increases the frequency of data transmission up to 40 Hz and reduces the sensor weight which can be important in motorsport applications. If the sensors are mounted on the outside of the wheel, as are some aftermarket systems, they are subject to mechanical damage, aggressive fluids, as well as theft. When mounted on the inside of the rim, they are no longer easily accessible for battery change and the RF link must overcome the attenuating effects of the tire which increases the energy need. A direct TPMS sensor consists of the following main functions requiring only a few external components — ''e.g.'' battery, housing, PCB — to get the sensor module that is mounted to the valve stem inside the tire: * pressure sensor; * analog-digital converter; * microcontroller; * system controller; * oscillator; * radio frequency transmitter; * low frequency receiver, and * voltage regulator (battery management). Most originally fitted dTPMS have the sensor mounted on the inside of the rim and the batteries are not exchangeable. A discharged battery means that the tire must be dismounted in order to replace it, so long battery life is desirable. To save energy and prolong battery life, many dTPMS sensors do not transmit information when parked (which eliminates spare tire monitoring) or apply a more power expensive two-way communication which enables wake-up of the sensor. For OEM auto dTPMS units to work properly, they need to recognize the sensor positions and must ignore the signals from other vehicles. Aftermarket dTPMS units not only transmit while vehicles are moving or parked, but also provide users with some advanced monitoring options including data logging, remote monitoring options and more. They are available for all types of vehicles, from motorcycles to heavy equipment, and can monitor up to 64 tires at a time, which is important for commercial vehicles. Many aftermarket dTPMS units do not require specialized tools to program or reset, making them much simpler to use.


Maintenance issues


Valve-stem corrosion

First-generation of TPMS sensors that are integral with the valve stem have suffered from corrosion. Metallic valve caps can become seized to the valve stem because of
galvanic corrosion Galvanic corrosion (also called bimetallic corrosion or dissimilar metal corrosion) is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. A sim ...
of dissimilar metals, and efforts to remove it can break the stem, destroying the sensor. A similar fate may befall an after-market brass valve core inside the stem that may have been installed by unwary technician, replacing the original specialized nickel-coated cores. (They can be distinguished by the yellowish colour of the brass.) Seizure of the valve can complicate repair of a tire leak, possibly requiring replacement of the entire sensor.


Tire sealant compatibility

There is controversy regarding the compatibility of after-market tire sealants with dTPMS that employ sensors mounted inside the tire. Some manufacturers of sealants assert that their products are indeed compatible, but others warned that the "sealant may come in contact with the sensor in a way that renders the sensor temporarily inoperable until it is properly cleaned, inspected and re-installed by a tire care professional". Such doubts are also reported by others. Use of such sealants may void the TPMS sensor warranty.


Benefits of TPMS

The dynamic behavior of a pneumatic tire is closely connected to its inflation pressure. Key factors like braking distance and lateral stability require the inflation pressures to be adjusted and kept as specified by the vehicle manufacturer. Extreme under-inflation can even lead to thermal and mechanical overload caused by overheating and subsequent, sudden destruction of the tire itself. Additionally, fuel efficiency and tire wear are severely affected by under-inflation. Tires do not only leak air if punctured, they also leak air naturally, and over a year, even a typical new, properly mounted tire can lose from 20 to 60
kPa KPA may refer to: * Keele Postgraduate Association, Keele University, UK, formerly Keele Research Association (KRA) * Kensington (Olympia) station, London, England, National Rail station code * Kenya Ports Authority * ''Kiln phosphoric acid'', a ...
(3 to 9
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), roughly 10% or even more of its initial pressure. The significant advantages of TPMS are summarized as follows: * Fuel savings: According to the GITI, for every 10% of under-inflation on each tire on a vehicle, a 1% reduction in fuel economy will occur. In the United States alone, the Department of Transportation estimates that under inflated tires waste of fuel each year. * Extended tire life: Under inflated tires are the number one cause of tire failure and contribute to tire disintegration, heat buildup, ply separation and sidewall/casing breakdowns. Further, a difference of in pressure on a set of duals literally drags the lower pressured tire 2.5 metres per kilometre (13 feet per mile). Moreover, running a tire even briefly on inadequate pressure breaks down the casing and prevents the ability to retread. It is important to note that not all sudden tire failures are caused by under-inflation. Structural damages caused, for example, by hitting sharp curbs or potholes, can also lead to sudden tire failures, even a certain time after the damaging incident. These cannot be proactively detected by any TPMS. * Improved safety: Under-inflated tires lead to tread separation and tire failure, resulting in 40,000 accidents, 33,000 injuries and over 650 deaths per year. Further, tires properly inflated add greater stability, handling and braking efficiencies and provide greater safety for the driver, the vehicle, the loads and others on the road. * Environmental efficiency: Under-inflated tires, as estimated by the US Department of Transportation, release over 26 billion kilograms (57.5 billion pounds) of unnecessary carbon-monoxide pollutants into the atmosphere each year in the United States alone. Further statistics include: The French Sécurité Routière, a road safety organization, estimates that 9% of all road accidents involving fatalities are attributable to tire under-inflation, and the German
DEKRA DEKRA is the world’s largest non-listed expert organization in the TIC sector (Testing, Inspection, Certification) founded in Berlin, Germany in 1925 as Deutscher Kraftfahrzeug-Überwachungs-Verein (German Motor Vehicle Inspection Association ...
, a product safety organization, estimated that 41% of accidents with physical injuries are linked to tire problems. The European Union reports that an average under-inflation of 40 kPa produces an increase of fuel consumption of 2% and a decrease of tire life of 25%. The European Union concludes that tire under-inflation today is responsible for over 20 million liters of unnecessarily-burned fuel, dumping over 2 million tonnes of CO2 into the atmosphere, and for 200 million tires being prematurely wasted worldwide. In 2018, a field study on TPMS and tire inflation pressure was published on the UN ECE Working Party on Brakes and Running Gear (GRRF) homepage. It covered 1,470 randomly selected vehicles in three EU countries with dTPMS, iTPMS and without TPMS. Main findings are that TPMS fitment reliably prevents severe and dangerous underinflation and hence yields the desired effects for traffic safety, fuel consumption and emissions. The study also showed that there is no difference in effectiveness between dTPMS and iTPMS and that the TPMS reset function does not present a safety risk.


Privacy concerns with direct TPMS

Because each tire transmits a unique identifier, vehicles may be easily tracked using existing sensors along the roadway. This concern could be addressed by encrypting the radio communications from the sensors but such privacy provisions were not stipulated by the NHTSA.


Heavy-duty vehicles

U.S.
National Highway Traffic Safety Administration The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rela ...
regulations only apply to vehicles under 10,000 pounds. For heavy-duty vehicles (Classes 7 and 8,
gross vehicle weight Vehicle weight is a measurement of wheeled motor vehicles; either an actual measured weight of the vehicle under defined conditions or a gross weight rating for its weight carrying capacity. Curb or kerb weight Curb weight (U.S. English) or kerb ...
greater than 26,000 pounds), most of the above-mentioned systems don't work well, requiring the development of other systems. The US Department of Transportation has commissioned several studies to find systems that work on the heavy-duty market specifying some goals that were needed in this market. The SAE has tried to disseminate best practices since legal regulations for heavy vehicles has been lagging.


Compulsory


America

The first country to have TPMS mandatory was the United States of America. In the early 2000s, numerous traffic accidents such as rollovers and tire blowouts occurred due to insufficient air pressure level. NHTSA regarded flat tires as a potential threat to safety which was soon followed by the enactment of the law on attaching TPMS for every vehicle in September 2007.


South Korea

TPMS became obligatory for every vehicle under 3.5t sold after 2013. Later in 2015, every vehicle had to have TPMS regardless of its size. In 2011, Hyundai Mobis successfully developed the TPMS and first applied it in the Veloster. As a result, the sensor's power usage is about 30% lower than that of existing products, reducing battery size and reducing sensor weight by more than 10%.


Icons


See also

* Central tire inflation system *
Cold inflation pressure Cold inflation pressure is the inflation pressure of tires before the car is driven and the tires(tyres) warmed up. Recommended cold inflation pressure is displayed on the owner's manual and on the placard (or sticker) attached to the vehicle d ...
*
Nira Dynamics AB NIRA Dynamics AB is a Swedish company focusing on research and development of signal processing and control systems for the automotive industry. It supplies automotive original equipment manufacturers (OEMs) and suppliers in Europe, North America, ...
*
Tire-pressure gauge A tire-pressure gauge, or tyre-pressure gauge, is a pressure gauge used to measure the pressure of tires on a vehicle. Since tires are rated for specific loads at certain pressure, it is important to keep the pressure of the tire at the opti ...
*
Loose wheel nut indicator A loose wheel nut indicator is a measuring tool that warns of loose wheel nuts, which is the most common cause of wheels on vehicles falling off. History In 1990, Mike Marczynski, who was responsible for a commercial vehicle, commercial vehic ...


References


External links

* {{DEFAULTSORT:Tire Pressure Monitoring System Automatic identification and data capture Vehicle safety technologies Automotive technologies Tires