235
Wheels and tyres
WARNING
●
Never adjust tyre pressure when the tyres are hot. This may damage
or even burst the tyres. Risk of accident!
●
An insufficiently inflated tyre flexes a lot more at high speeds and
causes significant heating of the tyre. Under these conditions, the tyre
bead may be released or the tyre may burst. Risk of accident!
For the sake of the environment
Under-inflated tyres lead to increased fuel consumption and tyre wear.
Significant tyre pressure loss
The tyre symbol is displayed and indicates that the tyre pressure
of at least one tyre is insufficient.
– Stop the vehicle.
– Switch the engine off.
– Check the tyre(s).
– Change the wheel if necessary.
Tyre service life
The service life of tyres is dependent on tyre pressure, driv-
ing style and fitting.
Fig. 152 Tyre tread wear
indicators
Fig. 153 Diagram for
changing wheels
Safety First
Operating Instructions
Practical Tips
Technical Specifications
236
Wheels and tyres
Wear indicators
The original tyres on your vehicle have 1.6 mm high “tread wear indicators”
⇒ fig. 152
, running across the tread. Depending on the make, there will be
6 to 8 of them evenly spaced around the tyre. Markings on the tyre sidewall
(for instance the letters “TWI” or other symbols) indicate the positions of
the tread wear indicators. The minimum tread depth required by law is
1.6 mm (measured in the tread grooves next to the tread wear indicators).
Worn tyres must be replaced. Different figures may apply in
export countries
⇒ .
Tyre pressure
Incorrect tyre pressure causes premature wear and could cause tyre blow-
out. For this reason, the tyre pressure should be checked at least once per
month
⇒ page 233.
Driving style
Fast cornering, heavy acceleration and hard braking all increase tyre wear.
Changing wheels around
If the front tyres are worn considerably more than the rear ones it is advisa-
ble to change them around as shown
⇒ fig. 153
. All the tyres will then last
for about the same time.
Wheel balance
The wheels on new vehicles are balanced. However, various factors encoun-
tered in normal driving can cause
them to become unbalanced, which re-
sults in steering vibration.
Unbalanced wheels should be rebalanced, as they otherwise cause exces-
sive wear on steering, suspension and tyres. A wheel must also be reba-
lanced when a new tyre is fitted.
Incorrect wheel alignment
Incorrect wheel alignment causes excessive tyre wear, impairing the safety
of the vehicle.
If tyres show excessive wear, you should have the wheel
alignment checked by an Authorised Service Centre.
WARNING
There is a serious danger of accidents if a tyre bursts during driving!
●
The tyres must be replaced at the latest when the tread wear indica-
tors are worn
⇒
page 236. Failure to do so could result in an accident.
Worn tyres do not grip well at high speeds on wet roads. There is also a
greater risk of aquaplaning.
●
At continuously high speeds, a tyre with insufficient pressure flexes
more. This causes it to overheat. This can cause tread separation and tyre
blow-out. Risk of accident. Always observe the recommended tyre pres-
sures.
●
If tyres show excessive wear, you should have the running gear
checked by an Authorised Service Centre.
●
Keep chemicals such as oil, fuel and brake fluid away from tyres.
●
Damaged wheels and tyres must be replaced immediately!
For the sake of the environment
Under-inflated tyres will increase fuel consumption.
237
Wheels and tyres
Run-flat tyres
Run-flat tyres allow you to continue driving even with a
punctured tyre, in the majority of cases.
In vehicles that are factory-fitted with run-flat tyres
1)
the loss of tyre
pressure is indicated on the instrument panel.
Driving with run-flat tyres (emergency running)
– Leave the ESC (ESP)/ASR (TCS) (Electronic Stability Control) acti-
vated, or activate it
⇒ page 183.
– Continue driving carefully and slowly (80 km/h maximum).
– Avoid sudden manoeuvres and sharp turns.
– Avoid driving over obstacles (for example kerbs) or potholes.
– Look out for the ESC (ESP)/ASR (TCS) intervening often, smoke
coming from the
tyres or the smell of rubber, the vehicle vibrat-
ing or a clattering noise. If any of these occur, stop the vehicle.
The run-flat tyres have a tag on the side of the tyre, with the description:
“DSST”, “Eufonia”, “RFT”, “ROF”, “RSC”, “SSR” or “ZP”.
The sides of this type of tyre are reinforced. When the tyres lose air they are
supported on the sides (emergency driving).
The loss of pressure in the tyre is shown on the instrument panel. You can
then drive a maximum of 80 km and if the circumstances are favourable (for
example, low load), even more.
The damaged tyre should be changed as soon as possible. The rim should
be checked in a specialist workshop to detect possible damage and replace
it if necessary. We recommend you contact Technical Service. If more than
one tyre is being used
under emergency conditions, this reduces the dis-
tance which can be travelled.
Starting driving in emergency conditions
When loss in tyre pressure is displayed on the instrument panel, this means
that at least one tyre is being driven in emergency conditions
⇒ .
End of emergency operation
Do not drive on if:
● smoke is coming from one of the tyres,
● there
is a smell of rubber,
● the vehicle vibrates,
● there is a rattling noise.
When is it no longer possible to continue driving even using run-flat tyres?
● If one of the tyres has been severely damaged in an accident, etc. If a
tyre has been badly damaged there is a risk that parts of the tread can be
thrown off and cause damage to the fuel lines, brake pipes or fuel filler.
● It is also advisable to stop driving if severe vibrations occur, or if the
wheel starts overheating and gives off smoke.
WARNING
When driving in emergency conditions, the driving quality of the vehicle
is considerably impaired.
●
The maximum permitted speed of 80 km/h is subject to road and
weather conditions. Please observe legal requirements when doing so.
●
Avoid sharp turns and rapid manoeuvres, and brake earlier than usu-
al.
1)
Depending upon version and country.
Safety First
Operating Instructions
Practical Tips
Technical Specifications
