BMW 5 Series: Electronic tire pressure label

Technical functional description

An electronic tire pressure label is being used for the first time at BMW. The tire pressure label sticker has been supplemented in the G30 by an additional user menu in the Central Information Display (CID).

Tire pressures are changing constantly depending on tire air temperature. A change in the tire air temperature for every +/- 10 ºC or +/- 18 ºF corresponds to a pressure increase or pressure decrease of +/- 0.1 bar or 1.4 psi. For this reason, you may see a warning message of insufficient tire pressure if your tires have cooled significantly. In many of these cases, there is not technical fault, but insufficient checking of the tire pressures which should be checked at regular intervals.

Unlike the tire pressure sticker, the electronic tire pressure label permanently monitors the nominal pressures taking into consideration the current temperatures. This means that it determines and displays the optimum tire pressure at any temperature.

Electronic tire pressures label in the G30

1. Electronic tire pressure label in the CID
2. Tire pressure information label

Once you have selected the relevant tire type (summer/winter), the tire size on the rear axle and max speed range, the appropriate tire pressures are output to the CID (nominal pressure). Following the input and before the teach-in drive, these correspond to the tire pressures on the tire pressure label.

The vehicle must then be driven so it can learn the new size wheels and tires. Once the teach-in drive has been successfully completed, the current optimum tire pressure taking into consideration the tire air temperatures is always displayed. This can differ from the information on the conventional tire pressure label on the B-pillar because it has taken the tire air temperatures into consideration. Correct tire pressures reduce fuel consumption and ensure greater driving safety.

The tire air temperatures are measured by the four wheel electronics units in the various wheels. Since the wheel electronics units do not begin transmitting until driving speed has reached 20 km/h (12 mph), it is not possible to determine this while the vehicle is parked. A substitute value can be formed using the outside temperature sensor when the vehicle is stationary for wheels that have already been taught-in (see the following chapter "Measurement of tire air temperatures when stationary").

When new wheels and tires are installed, for example during a wheel change in the workshop, the nominal pressure (cold tire pressure) can generally be used. When wheels are changed in the winter, however, the great temperature difference between the ambient temperature and the current temperature of the tire (difference between workshop temperature and ambient temperature) must be taken into consideration. In this case, the tire pressure from the conventional tire pressure label should be corrected upwards somewhat. A temperature difference for every +/- 10 ºC corresponds to approximately 0.1 bar tire pressure change.

Tire pressure in bar and temperature in ºC

1. Tire air temperature in ºC
2. Pressure in bar

A temperature difference for every +/- 18 ºF corresponds to approximately 1.4 psi of tire pressure change.

Tire pressure in psi and temperature in ºF

1. Tire air temperature in ºF
2. Pressure in psi

After the wheels have completed their teach-in drive, the nominal pressures can differ from the actual values determined and entered in the workshop. The background reason for this is the incorporation of the temperatures following a completed teach-in drive. The customer should be informed that although the tire pressures have been checked, these can constantly change depending on the temperature. However, the tire pressures should be adjusted again at an early opportunity if the difference is permanently more than 0.2 bar / 2.9 psi.

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