Volvo C70 Owner's Manual page 135

Wheels and tyres
General
Driving characteristics and tyres
The tyres greatly affect the car's driving
characteristics. 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
pressures specified on the tyre pressure
label, see page 138.
Designation of dimensions
The dimensions are stated on all car tyres.
Example: 215/55R16 91 W.
215 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).
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's
registration 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
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faster than the speed rating of the tyre (for
example, class Q can be driven at a maximum
of 160 km/h).
Remember that traffic regulations determine
how fast a car can be driven, not the speed
class of the tyres.
Note! Maximum permitted speeds indicated.
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
New tyres
Tyres are perishable. After a
few years they begin to
harden at the same time as
the friction capacity/charac-
teristics 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 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
undamaged. The reason for this is that tyres
age and decompose, even if they are hardly
ever or never used. The function can
therefore be affected due to the tyre's
constituent materials being broken down and
it 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.