Jaguar XJ (2008 year). Manual - part 65

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Wheels and Tires

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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.

Damage

Excessive local distortion can cause the 
casing of a tire to fracture and may lead to 
premature failure. Tires should be 
examined especially for cracked walls, 
exposed cords, etc. Flints and other 
sharp objects must be removed from the 
tire tread; if left in they may work through 
the cover. Clean off any oil or grease 
contamination by using a suitable cleaner.

Caution: Do not use paraffin 
(kerosene), because this has a 
detrimental effect on rubber.

Tire repair

Damaged tires should be replaced with 
new tires fitted. They must not be repaired 
in view of the high performance capability 
of the vehicle.

Tire replacement

When replacing tires, it is preferable to fit 
a complete vehicle set. If either front or 
rear tires only need to be renewed, new 
tires must be fitted as axle sets.

After new tires have been fitted the 
wheels need to be dynamically balanced.

Do not fit tires with a different tread 
pattern, size or speed rating.

The installation of replacement tires with 
steel cord body plies in the tire sidewall 
may cause malfunction of the TPMS and 
is not recommended (cord material 
information is moulded on the tire 
sidewall).

Additionally, if your vehicle was equipped 
with run-flat tires, replacing them with 
tires that are not identical to those 
originally fitted may cause malfunction of 
the TPMS, and is not recommended. 

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Wheels and Tires

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Always check your TPMS indicator after 
replacing one or more tires on your 
vehicle. 

Tire ageing

Tires degrade over time, even when they 
are not being used. It is recommended 
that tires generally be replaced after six 
years of normal service. Heat caused by 
hot climates or frequent high loading 
conditions can accelerate the ageing 
process.

You should replace the spare tire when 
you replace the other road tires due to the 
ageing of the spare tire.

263

Wheels and Tires

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TIRE QUALITY GRADES

United States Department of 
Transportation/Uniform Tire Quality 
Grades

The following information relates to the 
tire grading system developed by the 
National Highway Traffic Safety 
Administration which will grade tires by 
tread wear, traction and temperature 
performance.

Tread wear

The tread wear grade is a comparative 
rating based on the wear rate of the tire 
when tested under controlled conditions 
on a specified government test course. 
For example, a tire graded 150 would 
wear one and a half (1.5) times as well on 
the government course as a tire 
graded 100.

The relative performance of tires depends 
upon the actual conditions of their use, 
however, and may depart significantly 
from the norm due to variations in driving 
habits, service practices and differences 
in road characteristics and climate.

Traction - A, B, C

The traction grades, from the highest to 
the lowest are AA, A, B and C. The 
grades represent the tire’s ability to stop 
on wet pavements as measured under 
controlled conditions on specified 
government test surfaces of asphalt and 
concrete. A tire marked C may have poor 
traction performance.

!

WARNING:

The traction grade assigned to this tire 
is based on braking (straight ahead) 
traction tests and does not include 
acceleration, cornering hydroplaning 
or peak traction characteristics.

Temperature - A, B, C

The temperature grades A (the highest), B 
and C represents the tire’s resistance to 
the generation of heat and its ability to 
dissipate heat when tested under 
controlled conditions on a specified 
indoor laboratory test wheel.

Sustained high temperature can cause 
the material of the tire to degenerate and 
reduce tire life, and excessive 
temperature can lead to sudden tire 
failure.

The grade C corresponds to a level of 
performance which all passenger car tires 
must meet under the Federal Motor 
Vehicle Safety Standard No. 109.

Grades B and A represent higher levels of 
performance on the laboratory test wheel 
than the minimum required by law.

!

WARNING:

The temperature grade for these tires 
is established for a tire that is properly 
inflated and not overloaded. Excessive 
speed, under-inflation or excessive 
loading, either separately or in 
combination, can cause heat build-up 
and possible tire failure.

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WINTER (SNOW) TIRES

The tires fitted as original equipment are 
designed with a rubber compound, tread 
pattern and width specially suited for high 
speeds in normal road conditions, but 
they are less suitable during extremes of 
low temperatures, snow and ice. The use 
of winter tires will considerably improve 
the vehicle’s handling during these 
conditions.

It is recommended that only Jaguar 
approved winter tires are used 
(see page 274).

Tire directional indicators must be 
rotating in a clockwise direction when 
viewed from the right-hand side of the 
vehicle, and counter-clockwise when 
viewed from the left-hand side of the 
vehicle.

Do not exceed the tire speed rating when 
using winter tires.

Winter tires must be used in vehicle sets, 
that is, fitted on all four wheels.

SNOW CHAINS

Snow chains, of the recommended type, 
may only be fitted to rear wheels.

Contact your Jaguar Dealer for details 
and availability of approved snow chains.

The maximum speed when using snow 
chains is 48 km/h (30 mph).

Remove the snow chains immediately the 
roads are clear of snow.

Ensure the fitting instructions supplied 
with the snow chains are kept in a safe 
place, for example, with this literature 
pack.

Note: Dynamic Stability Control MUST be 
switched OFF when using snow chains.