Jaguar XJ (2008 year). Manual - part 62

249

Wheels and Tires

Wheels and Tires

TIRE PRESSURES

WARNING:

Improperly inflated tires can affect
vehicle handling and can fail suddenly,
possibly resulting in loss of vehicle
control.

Caution: Never exceed the maximum
pressure stated on the sidewall.
Over-inflation could cause the tire to
fail suddenly.

Note: It is an offence in certain countries
to drive a vehicle with tires that are not
inflated in accordance with the vehicle’s
proper use.

The recommended tire pressures are
displayed on the tire pressure label.
These tire pressures provide optimum
ride and handling characteristics for all
normal operating conditions.

In the interest of safety, reliability and fuel
efficiency, check the tires, including the
spare, for condition and pressure on a
weekly basis.

Pressure checks must be carried out
when the tires are cold and the vehicle
has been standing in ambient local
conditions for at least one hour.

Do not check tire pressures immediately
after the tires have travelled a distance of
one mile or more. Tire temperatures and
pressures increase when running.
Deflating a warm tire to the recommended
pressure will result in under-inflation. This
could be dangerous.

If tire pressures are checked while the
vehicle is inside a protected covered area,
e.g. a garage, and subsequently driven in
lower outdoor temperatures, tire
under-inflation could occur.

A slight pressure loss occurs naturally
with time. If this exceeds 14 kPa (2 psi,
0.14 bar) per week, have the cause
investigated and rectified by a qualified
technician.

Tire pressure label (Canada and
Mexico only)

A label giving the tire pressure information
is visible on the fuel filler flap.

Wheels and Tires

250

Tire pressure label/placard (USA only)

A tire information label is visible on the
pillar behind the driver’s door (also known
as the B pillar), giving information specific
to the wheel and tire equipment fitted to
the vehicle when it was built. The label
contains the following information:
• The maximum number of occupants

(1), divided between the front (2) and
rear (3) of the vehicle.

• The vehicle capacity weight (4), which

includes the weight of the driver,
passengers and cargo.

• Cold inflation pressures for the spare

tire and the front and rear tires (5).

• The size of the tires (6) with which the

vehicle was originally equipped.

Note: The label must not be changed,

even if different wheels are fitted at a
later stage.

Ambient temperature pressure
compensation

If the intended journey will take the vehicle
into an area where the ambient local
temperature is known to be lower than the
journey start point, tire pressure under
inflation could occur.

A colder ambient local temperature will
reduce pressure within the tire. An effect
is to decrease sidewall height and to
increase tire shoulder wear with the
potential for tire failure. Vehicle dynamics
could also be adversely affected.

In order to minimise this effect, tire
pressures can be adjusted to
compensate before the start of the
journey. Alternatively, tire pressures can
be adjusted when the area of lower
ambient temperature is reached.

In this situation the vehicle must be left in
the ambient local temperature for a least
one hour before tire pressure is adjusted.

JAG0761

E86402

251

Wheels and Tires

To compensate for colder ambient
temperatures, tire pressures should be
increased by 2 psi (0.14 bar / 14 kPa) for
each 10°C (20°F) decrease.

Note: Ensure that correct tire pressures
are maintained when moving to areas of
differing ambient temperature.

The Tire Pressure Monitoring System
(TPMS) may issue a warning if the
under-inflation becomes significant.
When driving through variable climatic
conditions the TPMS warnings may be
intermittent.

In areas of extended high ambient
temperature, vehicle tires can be affected
by a softening of the tire sidewall. If the
vehicle is stationary for long periods, the
effect is to slightly deform the tire at the
point where the tire meets the standing
surface. This is known as a flat spot.

This is normal tire behaviour, however,
when the vehicle is subsequently driven,
vibration may be experienced from the
deformed tire. The condition will steadily
improve with additional mileage.

In order to minimise this effect, tire
pressures can be adjusted before the
start of the journey to compensate.

For each 10°C (20°F) increase in
temperature above 20°C (68°F), tire
pressure should be increased by 2 psi
(0.14 bar / 14 kPa).

Tire pressure compensation chart -
high ambient temperatures

Tire Pressure Temperature

Compensation

Ambient

Temperature °C

(°F)

Pressure

Compensation

psi

(bar/kPa)

20 (68)

use placard label

30 (86)

+2 (0.14 / 14)

40 (104)

+4 (0.28 / 28)

50 (122)

+6 (0.41 / 41)

Wheels and Tires

252

Recommended Tire Pressures

The following table gives the tire
pressures for all recommended tire sizes.

Checking tire pressures

The following procedure should be used
to check and adjust the tire pressures:

1. Remove the valve cover.

2. Firmly attach a tire pressure

gauge/inflator to the valve.

3. Read the tire pressure from the

gauge. If required, add air to the tire.

4. If air is added to the tire, remove the

gauge from the valve and reattach it
before checking that the pressure is
correct. Failure to remove and
reattach the gauge from the valve
could cause the gauge to show an
incorrect reading.

5. If too much air is added, remove the

gauge from the valve and allow air out
of the tire by pressing the centre of the
valve. Reconnect the gauge to the
valve, and check that the air pressure
is correct.

6. Refit the valve cover.

A slight natural pressure loss occurs with
time. If this exceeds 2 psi (14 kPa, 0.14
bar, 0.14 kg/cm

) per week, the cause

should be investigated and rectified.

Note: It is an offence in certain countries
to drive a vehicle with tires that are not
inflated in accordance with the vehicle’s
proper use.

Tire Size

Tire Pressure

Front

Rear

235/50 R 18

30 psi, 210 kPa

32 psi, 220 kPa

255/40 R 19

32 psi, 220 kPa

34 psi, 230 kPa

255/35 R 20

34 psi, 230 kPa

36 psi, 250 kPa

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