2006 Lexus GS430 Scheduled Maintenance Guide / LEXUS 2006 GS430/GS300 FROM JAN. 2005 PROD. OWNER'S MANUAL (OM30649U)

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548
Uniform tire quality grading
This information has been prepared in accordance
with regulations issued by the National Highway
Traffic Safety Administration of the U.S. Department
of Transportation. It provides the purchasers and/or
prospective purchasers of Lexus vehicles with
information on uniform tire quality grading.
Your Lexus dealer will help answer any questions
you may have as you read this information.
DOT quality grades All passenger vehicle tires
must conform to Federal Safety Requirements in
addition to these grades. Quality grades can be
found where applicable on the tire sidewall between
tread shoulder and maximum section width. For
example: Treadwear 200 Traction AA Temperature
A
Treadwear − The treadwear 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 − 1/2) 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
AA, A, B, C − The traction grades, from highest
to lowest, are AA, A, B and C, and they represent the
tire’s ability to stop on wet pavement 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 cornering (turning) traction.
Temperature A, B, C − The temperature grades are A
(the highest), B, and C, representing 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 grades for this tire are
established for a tire that is properly inflated and not
overloaded. Excessive speed, underinflation, or
excessive loading, either separately or in combination,
can cause heat buildup and possible tire failure.

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Glossary of tire terminology
Tire related termMeaning
Cold tire inflation
pressuretire pressure when the vehicle has been parked for at least 3 hours or m\
ore, or it
has not been driven more than 1.5 km or 1 mile under that condition
Maximum inflation
pressurethe maximum cold inflation pressure to which a tire may be inflated and \
it is shown
on the sidewall of the tire
Recommended inflation
pressurecold tire inflation pressure recommended by a manufacturer
Accessory weight
the combined weight (in excess of those standard items which may be rep\
laced) of
automatic transmission, power steering, power brakes, power windows, pow\
er
seats, radio, and heater, to the extent that these items are available as
factory−installed equipment (whether installed or not)
Curb weight
the weight of a motor vehicle with standard equipment including the maxi\
mum
capacity of fuel, oil, and coolant, and, if so equipped, air conditionin\
g and
additional weight optional engine
Maximum loaded vehicle
weight
the sum of —
(a) curb weight;
(b) accessory weight;
(c) vehicle capacity weight; and
(d) production options weight

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Tire related termMeaning
Normal occupant weight68 kg (150 lb.) times the number of occupants specified in the second \
column of
Table 1 that follows
Production options weight
the combined weight of those installed regular production options weighi\
ng over
2.3 kg (5 lb.) in excess of those standard items which they replace, n\
ot previously
considered in curb weight or accessory weight, including heavy duty brak\
es, ride
levelers, roof rack, heavy duty battery, and special trim
Vehicle capacity weight
(Total load capacity)the rated cargo and luggage load plus 68 kg (150 lb.) times the vehicl\
e’s
designated seating capacity
Intended outboard
sidewall
(a) the sidewall that contains a whitewall, bears white lettering or bearsmanufacturer, brand, and/or model name molding that is higher or deeper than
the same molding on the other sidewall of the tire, or
(b) the outward facing sidewall of an asymmetrical tire that has a particula\
r side that must always face outward when mounted on a vehicle
Occupant distributiondistribution of occupants in a vehicle as specified in the third column \
of Table 1 that
follows
Rima metal support for a tire or a tire and tube assembly upon which the ti\
re beads are
seated
Rim diameter
(Wheel diameter)nominal diameter of the bead seat

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Tire related termMeaning
Rim size designationrim diameter and width
Rim type designationthe industry of manufacturer’s designation for a rim by style or code
Rim widthnominal distance between rim flanges
Vehicle maximum load on
the tirethe load on an individual tire that is determined by distributing to eac\
h axle its
share of the maximum loaded vehicle weight and dividing by two
Vehicle normal load on
the tirethe load on an individual tire that is determined by distributing to eac\
h axle its
share of the curb weight, accessory weight, and normal occupant weight
(distributed in accordance with Table 1 that follows) and dividing by two
Weather sidethe surface area of the rim not covered by the inflated tire
Table 1 – Occupant loading and distribution for vehicle normal load for various designated seating capacities
Designated seating capacity, Number of occupants
Vehicle normal load,
Number of occupantsOccupant distribution in a normally loaded vehicle
2 through 422 in front
5 through 1032 in front, 1 in second seat

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RUNFLAT TIRES
This vehicle can be equipped with either runflat
tires (RFT) or standard tires. You may continue
driving on the vehicle with runflat tires even if any
tire goes flat. It may be able to run for a maximum
of 160 km (100 miles) at a speed below 90 km/h (55
mph) after the low tire pressure warning light comes
on. When you drive your vehicle after the low tire
pressure warning light comes on, the tire must be
replaced. Do not use the repaired tire.
G63004
A “RFT” or “DSST” mark is molded on the sidewall of the
run−flat tire.
If you cannot distinguish between the standard tire and
run−flat tire, consult Lexus dealer.
If you have a flat tire, you have to take a different action
depending on whether the tires are standard tires or
run−flat tires.
Runflat tires characteristics:
The vehicle with run −flat tires helps you to continue
driving for up to 160 km (100 miles) at the moderate
speed and do not ever exceed 90 km/h (55 mph) even
with a flat tire. After such usage, the tire must be
replaced. If you are not sure, consult your Lexus dealer.
If you have a flat tire, decrease the speed and drive at
lower speed to reduce the extent to which the tire is
damaged.
However, in some conditions (such as at high
temperatures), you could not continue driving for up to
160 km (100 miles).
The use of non−genuine wheels may prohibit optimum
performance.
The run −flat tires equipped on this vehicle are ones
dedicated for GS430/300. Do not use them on another
model.
Do not mix run− flat tires with standard tires.
The tire warranty book covers the detailed information
on run− flat tires. For details, see the tire warranty book.
Tire pressure warning system
The tire pressure warning system is equipped to warn
you of the low tire inflation pressure. For details, see
“Tire pressure warning system” on page 433.

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TYPES OF TIRES
Determine what kind of tires your vehicle is originally
equipped with.
1. Summer tires
Summer tires are high −speed capability tires best suited
to highway driving under dry conditions.
Since summer tires do not have the same traction
performance as snow tires, summer tires are
inadequate for driving on snow −covered or icy roads.
For driving on snow− covered or icy roads, we
recommend using snow tires. If installing snow tires, be
sure to replace all four tires.
2. All season tires
All season tires are designed to provide better traction
in snow and to be adequate for driving in most winter
conditions, as well as for use all year round.
All season tires, however, do not have adequate traction
performance compared with snow tires in heavy or loose
snow. Also, all season tires fall short in acceleration and
handling performance compared with summer tires in
highway driving.
CAUTION
 Do not mix summer and all season tires on your
vehicle as this can cause dangerous handling
characteristics, resulting in loss of control.
 Do not use tires other than the manufacturer’s
designated tires, and never mix tires or wheels
of the sizes different from the originals as this
could result in loss of control and could cause
death or serious injury.

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ROTATING TIRES
G63008
To equalize tire wear and help extend tire life, Lexus
recommends that you rotate your tires according to
the maintenance schedule. (For scheduled
maintenance information, please refer to the
“Owner’s Manual Supplement / Scheduled
Maintenance”.) However, the most appropriate
timing for tire rotation may vary according to your
driving habits and road surface conditions.
The wheel assemblies must be rotated as illustrated
above.
When rotating tires, check for uneven wear and
damage. Abnormal wear is usually caused by incorrect
tire inflation pressure, improper wheel alignment,
out−of−balance wheels, or severe braking. Before storing radial, snow or studded tires, mark the
direction of rotation and be sure to install them in the
same
direction when using them again. Tires should be
stored in a cool dry place.
CHECKING AND REPLACING TIRES
When to replace your tires
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 1New tread 2Tread wear indicator
3Worn tread
Replace the tires when the tread wear indicators
show. The location of tread wear indicators is
shown by the ”TWI” or ”
Δ” marks, etc., molded on
the sidewall of each tire.

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The tires on your Lexus have built−in tread wear
indicators to help you know when the tires need
replacement. When the tread depth wears to 1.6 mm
(0.06 in.) or less, the indicators will appear. If you can
see the indicators in two or more adjacent grooves, the
tire should be replaced. Vehicles equipped with 245/40R18 93Y or
P245/40R18
93V tires: Your Lexus has been fitted with
specially developed tires which provide exceptional
dynamic performance under general road conditions.
However your riding comfort may worsen a little and
road noise may increase during driving. You may also
notice that your tires will wear more rapidly and tire grip
performance will be reduced on the snowy and/or icy
roads when compared to standard tires. Be sure to have
snow tires or tire chains on the snowy and/or icy roads
and drive carefully with the speed appropriate for road
conditions.
NOTICE
Low profile tire like 245/40R18 93Y or P245/40R18
93V may have greater damage than usual tires to
its tire wheel when receiving impact from the road
surface. Therefore, pay attention to the following.
 Be sure to use with proper tire inflation
pressure. If the tire inflation pressure is low, the
tire may have greater damage. For detailed
information about tire inflation pressure, see
page 534.
 Avoid driving onto high, sharpedged objects
and other road hazards. Failure to do so can
lead to severe tire damage.