Lexus 2003 SC430 Owner's Manual page 343

CHASSIS
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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Tire selection
When replacing a tire, use a tire of the same size and
construction, and the same or greater load capacity as the
originally installed tires.
Using any other size or type of tire may seriously affect
handling, ride, speedometer/odometer calibration, ground
clearance, and clearance between the body and tires or snow
chains.
CAUTION
Observe the following instructions.
accident may occur resulting in death or serious
injuries.
D Do not mix radial, bias belted, or bias–ply tires on
your vehicle, as this may cause dangerous handling
characteristics resulting in loss of control.
D Do not mix run–flat tires or standard tires on your
vehicle.
D Do not use tires other than the manufacturer's
recommended size, as this may cause dangerous
handling characteristics resulting in loss of control.
If you need to change from conventional tires to radial tires or
vice versa, replace them as a set.
Otherwise, an