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07 Wheels and tyres
144
General
07
Driving characteristics and tyres
The tyres greatly affect the car’s driving char-
acteristics. The type of tyre, dimensions, tyre
pressure and speed rating are important for
how the car performs.
When changing tyres, ensure that tyres of the
same type and dimensions, and preferably
also the same make, are fitted to all four
wheels. Follow the recommended tyre pres-
sures specified on the tyre pressure label, for
location see page 148.
Designation of dimensions
The dimensions are stated on all car tyres.
Example of designation: 205/55R16 91 W.
Speed ratings
The car is approved as a whole, which means
that dimensions and speed ratings must not
differ from those specified on the vehicle reg-
istration document. The only exception to
these conditions is winter tyres (both those
with metal studs and those without). If such a
tyre is chosen, the car must not be driven
faster than the speed rating of the tyre (for
example, class Q can be driven at a maxi-
mum of 160 km/h).
Remember that traffic regulations determine
how fast a car can be driven, not the speed
rating of the tyres.
Note! Maximum permitted speeds indicated.
New tyres
Tyres are perishable. After a
few years they begin to
harden at the same time as
the friction capacity/char-
acteristics gradually deteri-
orate. For this reason, aim
to get as fresh tyres as pos-
sible when you replace them. This is espe-
cially important with regard to winter tyres.
The week and year of manufacture, the tyre’s
DOT marking (Department of Transportation),
are stated with four digits, for example 1502.
The tyre in the illustration was manufactured
in week 15 of 2002.
Tyre age
All tyres older than six years should be
checked by an expert even if they seem un-
damaged. The reason for this is that tyres
age and decompose, even if they are hardly
ever or never used. The function can there-
fore be affected due to the tyre’s constituent
materials being broken down. The tyre
should then not be used. This also applies to
spare tyres, winter tyres and tyres saved for
future use. Examples of external signs which
indicate that the tyre is unsuitable for use are
cracks or discoloration.
The age of the tyre can be determined by the
DOT marking, see illustration above.
205 Section width (mm)
55 Ratio between section height and
width (%)
R Radial ply
16 Rim diameter in inches (")
91 Tyre load index (in this case 615 kg)
W Speed rating (in this case 270 km/h).
Q 160 km/h (used only on winter tyres)
T 190 km/h
H 210 km/h
V 240 km/h
W 270 km/h
Y 300 km/h