It started out so easy, but now it's over. Somehow this is related to the addition of the rear wheels. Actually, one would also have to consider the drive, so if necessary also the front wheels. Why? Because the wheel diameter can change due to acceleration. It is probably the smaller the further the contact area moves forward. Of course, this also applies to braking, only in the opposite direction.

Where does this complexity come from? Probably because one wants to warn relatively early and not only at a loss of 0.5 bar. The system now has to know what it is allowed to measure and accordingly learn from the control units for the drive and chassis, for example, whether the situation is normal. To explain what is still being evaluated, here is the example of a ball that behaves completely differently depending on the pressure, and can easily irritate even experienced players.

It is precisely this vibration behavior that is now used to experience the filling pressure somewhat more independently of the strain. But that would be an example in which the control unit has to know the vibration behavior under normal circumstances. One can easily imagine that it depends on the diameter and especially on the cross-section of a tyre. Already the difference between summer and winter tires should be noticeable here.

We would have at least given one reason why you have to recalibrate the system after changing from summer to winter tires, for example. Luckily, the driver can do this himself/herself with a process described in the operating instructions. Although the safety provided by the tyre pressure control has long since been sufficient, the aim is apparently to increase the level of accuracy. Then the tyre condition would also have to be specified during the calibration.

Why? Because then the system can detect wear and tear below the minimum and pass it on accordingly. We are slowly being threatened by American conditions in which the simple remounting of tires is possibly enriched with measurements in such a way that customers leave everything to the workshop and get used to leave the car only for very short periods of time to fill up the tank, of course a payment system with a card the petrol pump as expected with the electric car.

With the other tyre pressure monitoring system there is already all this. Funny that a 'trade journal' describes a comprehensive description of changing wheels in a supplement for its customers. Of course, a simple scissor jack is not enough for such an adventure. What is not said, however, is that, for example, the whole campaign is not enough for the Volvo shown, because it has to go to the workshop with a special kind of control system in the end. So is all the effort worth it?

Why does it have to go to the workshop? First, a pressure sensor is added to each wheel. And to answer the question right now, these change when you switch wheels. And since of course only radio contact to the wheel sensors is possible, unless you want to install a much more complex system, the control unit must be informed. No, it then knows which sensor is where, either through antennas above the wheel arches or, in the case of a central antenna, in the direction from which the signals are coming.

You guessed it, the power supply is one of the Achilles' heels here. How long does a battery last in a tyre like this? Because you can't choose them too big either, because that would cause problems for balancing. What one absolutely wanted to avoid and have now achieved, the time that a tyre spends on the rim is usually sufficient. An additional disassembly/assembly with subsequent balancing because of a used up battery is not absolutely necessary.

Additional effect: Anyone who has been driving the tyres for well over ten years, for example, receives a nudge towards common sense. Nevertheless, the pressure sensors are not without problems. During disassembly and assembly, care must be taken not to damage the sensor, which is easily possible given the machine power involved. Of course, in principle, the should be replaced at each tyre assembly, which often does not use its service life in any way. There is also an unbelievable number that the tyre trade will probably have to order first.

And how did you manage to increase the battery life? Sounds easy, but it's not quite so: the connection is not maintained all the time. However, such a system, as e.g. the theft warning, cannot be switched off completely. One speaks of sleep mode, in which it is protected from moisture in the tyre. So it has to be an active sensor with a small microprocessor and, of course, a lithium-ion battery. In addition to the pressure, it also reports the temperature in the tyres and possibly also the remaining capacity of the battery.

Pressure and temperature are important primarily because they allow the pressure to be converted to the same temperature at which the system was calibrated. Now, data can either be transmitted at regular data can be transmitted at regular intervals or, if appropriate antennas are available, data can be retrieved as required. If there is only a single antenna in the vehicle, it can be arranged in such a way that the radio signals from/to the wheel sensors cover different distances. From this, the evaluating device recognizes the position of the wheel sensor from which the data is currently coming.

All in all a more comfortable tyre pressure control system. You can recognize it, for example, by the fact that the tyre pressures can always be displayed. And depending on how sporty you are on the road or with how much load, the temperatures in the tyres can also be interesting. However, it is and will remain a system with significantly higher costs and sensitivity when disassembling/assembling and balancing. By the way, without the development of the lithium-ion battery, it would probably not have been possible to implement it in a meaningful way.