How do tire monitoring systems work?

This is how tire pressure monitoring systems work

Automatic air pressure monitoring helps save fuel and can prevent accidents. There are direct and indirect measuring systems - with different advantages and disadvantages.

  • Car manufacturers use different measurement systems

  • Control systems constantly monitor the tire pressure

  • TPMS has been mandatory for new cars for several years

Since 2014, according to ECE-R 64, all new cars have to have a Tire pressure control system (TPMS) equipped, which should, among other things, help prevent accidents caused by incorrect tire pressure or creeping flat feet. With a optimal air pressure but above all, it saves fuel and avoids unnecessary tire wear.

The Automaker either use direct sensors in the wheel or evaluate the rolling behavior of the tires. Both TPMS systems (also: tire pressure monitoring systems TPMS) have advantages and disadvantages.

Directly measuring TPMS systems

Direct measuring TPMS use on every single wheel Pressure and temperature sensorsthat are in direct contact with the air in the tire. They are used to determine the relevant physical parameters in real time and transmit them telemetrically to the control unit in the vehicle. As a rule, the driver also finds out about this Tire pressure value for each individual wheel position. The accuracy of the pressure measurements is approx. 0.1 bar or even less. Even slight fluctuations in pressure or temperature can be detected and displayed at an early stage.

Most of them lie Sensor housing the directly measuring TPMS on the Inside of the rim or tire in the area of ​​the valve and are fastened together with it. The sensor units draw the necessary power from batteries, which have to be replaced after about six to ten years. Because of the mandatory equipment both sets of wheels, i.e. summer and winter bikes, be equipped with the sensors.

The advantages the direct measuring TPMS:

  • The relevant physical parameters air pressure and temperature are measured very precisely and quickly on all four wheels - even creeping air losses are recognized and reported in good time.

  • The measured values ​​are usually displayed for each individual wheel.

  • After the sensors have been "taught in" for the first time, modern sensors do not need to be re-initialized after each tire pressure correction and wheel change.

The Disadvantage:

  • A separate sensor is required for each additional wheel. This means that buying a second set of wheels costs between € 120 and € 300.

  • Depending on the life expectancy of the batteries, most sensors need to be replaced after approx. Five to eight years.

Indirectly measuring TPMS systems

Indirectly working TPMS register changes to the wheels and thus only indirectly determine the tire pressure. If the tire pressure is too high or too low, that changes too Rolling behavior the tire: So increases z. B. the speed, because the rolling radius of the tire decreases with decreasing internal pressure. The vibration behavior of the tire casing also changes with the tire pressure. About the Speed ​​sensorson the four wheels the vehicle electronics recognize these changes in tire rolling behavior and notify the driver that the air pressure must have changed.

The advantage the indirect measurement:

  • Because the sensors already available in the vehicle are used, there are no additional costs when retrofitting to other wheels. After correcting the tire pressure or moving the wheels, the driver only has to reinitialize the system by pressing a button.

The Disadvantage:

  • The indirectly working TPMS usually reacts more slowly to a pressure loss than a directly measuring system. This applies in particular to the normal pressure loss caused by diffusion, which occurs in the same way on all wheels and thus keeps the difference between the wheels small.

  • The indirect systems do not come close to the accuracy of the direct measuring TPMS. It is also often not shown in which wheel the pressure loss exists - if a message is received, all wheels must be checked.

The majority of the Automaker equips your vehicles with direct measuring TPMS systems. Among the manufacturers who - with the exception of individual models - predominantly on direct measuring systems set, count among other things Mercedes, BMW, Ford, Hyundai, Kia, Toyota, Volvo, Renault, Nissan, Subaru, Jaguar, Alfa and Porsche.

Systems measuring indirectly mainly use the VW Group (VW, Audi, Seat, Skoda), PSA (Citroën, Peugeot, DS, Opel), Fiat, Mazda or Honda.

Here you will find the complete list of manufacturers with the TPMS used in each case.
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This is why tire pressure monitoring systems are so important

A constantly correct tire inflation pressure has a central, often underestimated importance for you economical and safe Operation of the vehicle. A tire inflation pressure that is too low increases the Rolling resistance the tire and thus the Fuel consumption: With a tire pressure of 0.5 bar, depending on the basic consumption, a Additional fuel consumption from 0.2 to 0.4 l / 100 km can be calculated.

Also the Mileage of tires that are operated with insufficient internal pressure are reduced: A tire underpressure of 20 percent leads to an estimated loss of mileage of 15 to 30 percent for the tire.

But the correct tire pressure is of course at least as important for them Driving safety of the vehicle. Not only when cornering - especially on wet surfaces - tires with insufficient inflation significantly degrade.

Tire pressure is also of particular importance for them Structural strength the tires and thus for acute driving safety - especially on longer motorway journeys at relatively high speeds. If in this situation - e.g. on long trips on vacation with a fully loaded vehicle - creeping loss of air weakens the tire unnoticed, this can lead to serious accidents. Of course, this also applies to the many undiscovered ones Stab wounds on the tires, which cause a slow loss of pressure over a long period of time.

You should keep this in mind with TPMS

  • Familiarize yourself with the specific tire pressure monitoring system of your vehicle. The most important individual information is contained in the operation manual. The reference to tire pressure sensors suggests that the TPMS measures the tire pressure directly. Notes such as "The system does not measure the actual tire pressure in the tires" indicate an indirectly working system.

  • If in doubt, check with yours Authorized Dealer and or Vehicle manufacturerwhether your vehicle is equipped with a TPMS.

  • At indirectly working TPMS You usually do not incur any additional costs when changing a wheel or tire, as no sensors need to be installed or serviced on the rims of the wheels themselves. However, you must reinitialize the system after changing the wheels, tires or the tire inflation pressure, as these systems must know the correct initial state of the wheels. To do this, you must set the prescribed pressure values ​​in all wheels as precisely as possible before initialization. Details can be found in the operating instructions.

  • At directly measuring systems the sensors located in the wheel must be checked by the fitter every time the tire is fitted. You should therefore inform the tire fitting company when making an appointment that your vehicle has a direct measuring TPMS. Especially if you order a second set of wheels with winter tires. In order to avoid misunderstandings, you should have the vehicle documents ready so that you can make an appointment.

  • Despite TPMS there is one regular air pressure control indispensable. Therefore, independently of the tire pressure monitoring, check the tire pressure at least every 14 days.

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