Jaguar XK. Service manual - part 55

223

Wheels and tires

TIRE CARE

All of the vehicle's tires (including the
spare) should be checked regularly for
damage, wear and distortion. If you are in
any doubt about the condition of a tire,
have it checked immediately by a tire
repair centre, or your Jaguar Dealer.

Tire pressures

WARNINGS

Defective tires are dangerous. Do
not drive the vehicle if a tire is
damaged, excessively worn, or

incorrectly inflated. Doing so may lead to
premature tire failure.

Avoid contaminating the tires with
vehicle fluids as they may cause
damage to the tire.

Avoid spinning the wheels. The
forces released can damage the
structure of the tire, and cause it

to fail. Doing so may lead to premature
tire failure.

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.

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.

Wheels and tires

224

Recommended tire pressures

If winter tires are fitted, please refer to the
winter tire pressure information. See
USING WINTER TIRES (page 227).

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

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 vehicle has travelled in excess of
1.6 kilometers (1.0 mile). tire
temperatures and pressures increase
when running. Deflating a warm tire to the
recommended pressure will result in
under-inflation.

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 0.14 bar (2
lbf/in², 14 kPa,) per week, have the cause
investigated and rectified by qualified
assistance.

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.

This table gives the tire pressures for all recommended tire sizes.

Tire pressure

Front

Rear

245/45ZR18 100Z

30 psi (210 kPa)

275/40ZR18 103Z

33 psi (227.5 kPa)

245/40ZR19 94Y

30 psi (210 kPa)

275/35ZR19 96Y

33 psi (227.5 kPa)

255/35ZR20 97Y

30 psi (210 kPa)

285/30ZR20 99Y

33 psi (227.5 kPa)

19 inch run-flat:

245/40R19 94Y

30 psi (210 kPa)

275/35R19 96Y

33 psi (227.5 kPa)

Temporary use spare wheel (front
and rear)

60 psi (420 kPa)

225

Wheels and tires

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.

To compensate for colder ambient
temperatures, tire pressures should be
increased by 0.14 bar (2 psi, 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
flat spot. The condition will steadily
improve with additional mileage.

In order to minimise this effect, tire
pressures can be adjusted to
compensate.

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

E91696

E91697

Wheels and tires

226

Tire pressure compensation chart
- high ambient temperatures

Tire pressures during long term
vehicle storage

To minimise the possibility and effects of
flat spots during storage, the tires may be
inflated to the maximum pressure
indicated on the tire wall.

Note: Before using the stored vehicle on
the road again, ensure that correct tire
pressures are restored.

Wear

All tires fitted as original equipment
include Tread Wear Indicators (TWI) in
their tread pattern. When the tread has
worn to a remaining depth of 1.6 mm the
indicators appear at the surface as bars
which connect the tread pattern across
the full width of the tire.

It is illegal, in certain countries, to
continue to use tires after the tread has
worn to less than 1.6 mm over three
quarters of the width and the entire
circumference of the tire.

It should be noted that the properties of
many tires alter progressively with wear.
In particular the wet grip and aquaplaning
resistance are gradually but substantially
reduced. Extra care and speed restriction
should therefore be exercised on wet
roads as the effective tread depth
diminishes.

Incorrect wheel alignment will accelerate
tire wear. If there is wear on the inner or
outer edges of the tread pattern it will be
advantageous to have the cause
detected by having the wheel alignment
checked.

Do not interchange tires from side to side,
front to rear or vice versa.

Note:

On all models the rear wheel and tire
assemblies are larger than the front.
These larger assemblies must never be
fitted to the front of the vehicle.

Note: On certain models the tires may be
directional type. These tires must be fitted
so that when viewed from the side of the
vehicle, direction of rotation arrow, on the
tire wall, points in the vehicle forward
direction of travel when positioned at the
top of the tire.

Tire Pressure Temperature

Compensation

Ambient

Temperature

°C (°F)

Pressure

Compensation bar

(psi, kPa)

20 (68)

use placard label

30 (86)

+ 0.14 (2, 14)

40 (104)

+ 0.28 (4, 28)

50 (122)

+ 0.41 (6, 41)

E91698

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