Tread Wear Indicators On The Tyres; Checking Tyre Pressure - Volvo XC90 TWIN ENGINE 2019 Owner's Manual

WHEELS AND TYRES

Tread wear indicators on the tyres

Tread wear indicators show the status of the
tyre's tread depth.
A tread wear indicator is a narrow elevation
across the longitudinal grooves of the tyre's
tread pattern. On the side of the tyre are the
letters TWI (Tread Wear Indicator). When the
tyre's tread depth is down to 1.6 mm (1/16
inch), the tread will be level in height with the
tread wear indicators. Change to new tyres as
soon as possible. Remember that tyres with
little tread depth provide very poor grip in rain
and snow.
Related information
Tyres (p. 592)
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596

Checking tyre pressure

Correct tyre pressure helps to improve driv-
ing stability, save fuel and extend the service
life of the tyres.
Tyre pressure decreases over time, this is a
natural phenomenon. Tyre pressure also varies
depending on ambient temperature. Driving
on tyres with tyre pressure that is too low
could result in the tyres overheating and being
damaged. Tyre pressure affects travelling
comfort, road noise and driving characteris-
tics.
Check the tyre pressures monthly. Use the
recommended tyre pressure for cold tyres in
order to maintain good tyre performance. Tyre
pressure that is too low or too high may cause
uneven wear on the tyres.
WARNING
Tyre pressure that is too low is the
•
most common cause of tyre failure and
may result in serious cracks in the tyre,
the tread loosening or the tyre explod-
ing, with unexpected loss of control of
the car and increased risk of personal
injury.
Tyres with pressure that is too low
•
reduce the load capacity of the car.
Cold tyres
The tyre pressure must be checked when the
tyres are cold. Tyres are considered cold when
they have the same temperature as the sur-
rounding air. This temperature is normally
reached when the car has been parked for at
least three hours.
After having driven approximately 1.6 km
(1 mile) these tyres are considered as warm. If
you have to drive further than this to inflate the
tyres, first check and record the tyre pressure
and inflate to a suitable tyre pressure when
you arrive at the pump.
When the outside temperature changes, the
tyre pressure also changes. A decrease in tem-
perature of 10 degrees causes the tyre pres-
sure to decrease 1 psi (7 kPa). Check the tyre
pressure regularly and adjust to the correct
pressure, which is specified on the car's tyre
information decal or certification label.
If you check the tyre pressure when the tyres
are warm then you must never release any air.
The tyres are warm due to driving and it is nor-
mal for the pressure to increase above the rec-
ommended pressure for cold tyres. A warm
tyre with tyre pressure equal to or below the
recommendation for cold tyres may have a
pressure that is far too low.