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Runflat indicator RPA
Principle
The system does not measure the tyre pres‐
sures as such.
It detects a pressure loss on the basis of a com‐
parison between the speeds at which the indi‐
vidual wheels rotate while the vehicle is in mo‐
tion.
If a tyre loses pressure, its diameter changes.
This in turn alters the rotational speed of the
corresponding wheel. This is detected and re‐
ported as a flat tyre.
Operating requirements
The system must have been initialised with cor‐
rect tyre inflation pressure, otherwise reliable
signalling of a flat tyre cannot be assured. Each
time the tyre pressure is adjusted or a tyre or
wheel is changed, initialise the system again.
System limits
Sudden tyre damage
No warning can be given of extreme, sud‐
den tyre failure caused by external factors.◀
A natural, even loss of pressure in all four tyres
that occurs over time is not detected. Conse‐
quently, check the tyre pressures at regular in‐
tervals.
In the following situations, the system could be
slow to respond or operate incorrectly:
▷
If the system has not been initialised.
▷
When driving on snow-covered or slippery
surfaces.
▷
When driving enthusiastically, causing the
driven wheels to spin, high lateral accelera‐
tion.
▷
Driving with snow chains.
Online Edition for Part no. 01 40 2 900 867 - 03 12 490
Security
Status display
The current status of the runflat indicator can be
shown on the control display, for example
whether the runflat indicator is active.
1.
"Vehicle information"
2.
"Vehicle status"
3.
"Flat Tyre Monitor"
The status is displayed.
Initialising
On initialisation, the current tyre pressures are
stored as a reference for detection of a flat tyre.
The initialisation is started by confirming the
correct inflation pressures.
When driving with snow chains fitted, do not in‐
itialise the system.
1.
"Vehicle information"
2.
"Vehicle status"
3.
"Confirm tyre pressure"
4.
Start the engine – do not drive off.
5.
Start the initialisation with "Initialise tyre
pressure".
6.
Drive off.
Initialising is completed while the vehicle is in
motion; this process can be interrupted at any
time.
Initialising resumes automatically when you
continue your journey.
Indication of a flat tyre
The yellow warning light is illuminated.
A Check Control message is displayed.
There is a flat tyre or substantial loss of
tyre pressure.
1.
Reduce your speed and cautiously stop the
car. Avoid violent or sudden braking and
steering manoeuvres.
2.
Check whether the vehicle is equipped with
standard tyres or run-flat tyres.
Controls
95
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