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 pres-
sures specified on the tyre pressure label, see
page 298.
Designation of dimensions
The dimensions are stated on all car tyres.
Example of designation:
235/60R18 103 V.
235 Tyre width (mm)
60 Ratio between tyre wall height and
tyre width (%)
R Radial ply
07
18 Rim diameter in inches (")
103 Tyre load index (in this case 615 kg)
V Speed rating for maximum permitted
speed (in this case 240 km/h).
184
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
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 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 illustration was manufactured in
week 15 of 2010.
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