07 Wheels And Tyres; General - Volvo XC90 Owner's Manual

07 Wheels and tyres

General

Driving characteristics and tyres
The tyres greatly affect the car's driving cha-
racteristics. 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, for location
see page 171.
Designation of dimensions
The dimensions are stated on all car tyres.
Example of designation:
225/70R16 102 H.
225 Section width (mm)
70 Ratio between section height and
width (%)
R Radial ply
07
16 Rim diameter in inches (")
102 Tyre load index (in this case 615 kg)
H Speed rating for maximum permit-
ted speed (in this case 210 km/h).
168
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 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 deteriorate.
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 decom-
pose, 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. In such a case 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.