Lexus 2003 LS Owner's Manual page 391

Any tires which are over 6 years old must be checked by
a qualified technician even if damage is not obvious.
Tires deteriorate with age even if they have never or seldom
been used.
This also applies to the spare tire and tires stored for future
use.
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.
CHASSIS
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