5 Series E34 525td (M51) TOUR
VS-42 je
Baugruppe/Group: 36
36 01 04 (078)
weltweit
Datum/Date: 01/
2004
Update: 11/2006
Run Flat Indicator
All models
Introduction
The Run Flat Indicator (RPA) monitors the tyre pressure throughout the journey.
The entire vehicle weight is carried by the air pressure in the tyres. If the pressure in one of the tyres should drop, the
tyre will gradually "cave in". The resulting flexing means that the defective tyre will quickly receive additional damage.
The tyre could burst.
Some 80 % of all flat tyres are caused by small holes (e.g. caused by nails). The holes result in a gradual loss of
pressure in the affected tyre. Many "tyre blowouts" can be traced back to preliminary damage caused by a gradual
loss of pressure.
A gradual loss of pressure in one tyre may remain unnoticed for a long time. The lack of pressure only makes itself
clearly felt when driving when the tyre is almost completely empty.
As tyre pressure drops, the radius of the wheel and with it the tyre's rolling circumference will also decrease. The
upshot is that the wheel speed of the affected tyre is increased.
The RPA records the wheel speeds using the wheel-speed sensors of the Dynamic Stability Control (DSC). The RPA
compares the speeds of the individual wheels and computes an average speed. In this way the RPA is able to detect
a loss of tyre pressure.
The RPA detects a drop in pressure below about 30 %
±
10 % of the initial value. The RPA indicator and warning
light indicates a drop in tyre pressure. The RPA will indicate this after just a short distance, as a rule after a few
minutes, from a certain minimum speed (e.g. 25 km/h) up to the permissible top speed.
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Different control units for the Run Flat Indicator [System overview ...]
SBT Run Flat Indicator All models
BMW AG - TIS
23.01.2013 11:53
Issue status (12/2007) Valid only until next DVD is issued
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