Lexus LX 470 1998 Owner's Manual page 293

CHASSIS
If you have tire damage such as cuts, splits, cracks deep enough
to expose the fabric, or bulges indicating internal damage, the
tire should be replaced.
If a tire often goes flat or cannot be properly repaired due to the size
or location of a cut or other damage, it should be replaced. If you are
not sure, consult with your Lexus dealer.
If an air loss occurs while driving, do not continue driving with a
deflated tire. Driving even a short distance can damage a tire beyond
repair.
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.
276
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.
These quality grades are molded on the sidewall.
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 A, B, C − The traction grades, from highest to lowest, are
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.