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09 Wheels and tyres
09
312
Tyres - maintenance
Amongst other things, the function of the
tyres is to carry load, provide grip on the road
surface, dampen vibration and protect the
wheel from wear.
Driving characteristics
Tyres greatly affect the car's driving characte-
ristics. The type of tyre, dimensions, tyre
pressure and speed rating are important for
how the car performs.
Tyre age
All tyres older than 6 years old should be
checked by an expert even if they seem
undamaged. Tyres age and decompose, even
if they are hardly ever or never used. The
function can therefore be affected. This
applies to all tyres that are stored for future
use. Examples of external signs which indi-
cate that the tyre is unsuitable for use are
cracks or discoloration.
New tyres
Tyres are perishable. After a few years they
begin to harden at the same time as the fric-
tion capacity/characteristics gradually deteri-
orate. For this reason, aim to get as fresh
tyres as possible when you replace them.
This is especially important with regard to
winter tyres. The last four digits in the
sequence mean the week and year of manu-
facture. This is the tyre's DOT marking
(Department of Transportation), and this is
stated with four digits, for example 1510. The
tyre in the figure was manufactured in week
15 of 2010.
Summer and winter wheels
When summer and winter wheels are
changed the wheels should be marked with
which side of the car they were mounted on,
for example L for left and R for right.
Wear and maintenance
Correct tyre pressure (p. 314) results in more
even wear. Driving style, tyre pressure, cli-
mate and road condition affect how quickly
your tyres age and wear. To avoid differences
in tread depth and to prevent wear patterns
(p. 314) arising, the front and rear wheels can
be switched with each other. A suitable dis-
tance for the first change is approx. 5000 km
and then at 10000 km intervals. Volvo recom-
mends the an authorised Volvo workshop is
contacted for checking if you are uncertain
about tread depth. If significant differences in
wear (> 1 mm difference in tread depth)
between tyres have already occurred, then
the least worn tyres must always be fitted on
the rear. Understeer is normally easier to cor-
rect than oversteer, and leads to the car con-
tinuing forwards in a straight line rather than
having the rear end skidding to one side,
resulting in possible complete loss of control
over the car. This is why it is important for the
rear wheels never to lose grip before the front
wheels.
Wheels with tyres fitted must be stored lying
down or hanging up - never standing up.
WARNING
A damaged tyre may lead to loss of control
over the car.
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