Volvo XC 90 Owner's Manual page 389

snaking. The function is included in the stability
5
system ESC .
Reasons for snaking
The snaking phenomenon can occur with any
car/trailer combination. Snaking normally occurs
at high speeds. But, there is a risk of it occurring
at lower speeds if the trailer is overloaded or the
load is improperly distributed, e.g. too far back.
In order for snaking to occur, there must be a
triggering factor, e.g.:
•
Car with trailer subjected to a sudden and
powerful side wind.
•
Car with trailer drives on an uneven road sur-
face or in a pothole.
•
Sweeping steering wheel movements.
If snaking has started, it could be difficult or even
impossible to suppress. This makes the car/
trailer combination difficult to control and there is
a risk that you could, for example, end up in the
wrong lane or leave the carriageway.
Trailer Stability Assist function
The trailer stability assist function continually
monitors car movements, particularly lateral
movements. If snaking is detected, the front
wheels are individually braked. This serves to sta-
bilise the car/trailer combination. This is often
enough to help the driver regain control of the
car.
Electronic Stability Control (Electronic stability control)
5
If snaking is not eliminated the first time that
trailer stability assist comes into action, the car/
trailer combination is braked with all wheels and
engine power is reduced. Once snaking has been
gradually suppressed and the car/trailer combi-
nation is stable once again, the system stops
regulating and the driver once again has full con-
trol of the car.
NOTE
The stability function is deactivated if the
driver selects Sport mode by deactivating
ESC via the menu system in the centre dis-
play.
The trailer stability assist may fail to engage if the
driver uses severe steering wheel movements to
try to rectify the snaking because in such a situa-
tion the system cannot determine whether it is
the trailer or the driver that is causing the snak-
ing.
When trailer stability assist is
operating, the ESC symbol
flashes in the driver display.
STARTING AND DRIVING
Related information
•
Driving with a trailer (p. 384)
•
Driving with a trailer under special conditions
(p. 386)
•
Electronic stability control (p. 254)
387