the same and effectively the same features are provided with the same reference characters unless otherwise stated fig1 shows a vehicle wheel with a tire 1 fitted with a piezoelectric element the tire rolling in the direction of rotation 2 the rolling behavior is shown here in idealized form on level ground 3 there is a flattened footprint that is referred to as the contact area 4 the length l of the contact area is measured here from the entry into the contact area 5 to the exit from the contact area 6 the shape of the contact area 4 is dependent among other things on characteristic data of the tire the wheel loading the tire pressure and the speed of the vehicle a wheel unit 7 is disposed in the tire 1 this comprises among other things a piezoelectric element which is disposed on the inside of the tire such that it is deformed when passing through the contact area in particular an intensive deformation of the piezoelectric element occurs on entering the contact area 5 and on exiting from the contact area 6 as a result of kinking besides the piezoelectric element the wheel unit 7 further comprises a battery a processor different sensors such as an air pressure sensor a temperature sensor and an acceleration sensor a processing unit and a transmitter if the piezoelectric element is deformed by a mechanical force it produces an electrical voltage that is a measure of the deformation of the piezoelectric element fig2 a and 2 b show the piezoelectric element 8 at different positions of the tire 1 the tire 1 shown in fig2 a is new whereas the tire 1.