749
Maintenance
4. Tire ply composition and material
The number of layers or plies of rub-
ber-coated fabric are in the tire. Tire
manufacturers also must indicate the
materials in the tire, which include
steel, nylon, polyester, and others.
The letter "R" means radial ply con-
struction; the letter "D" means diago-
nal or bias ply construction; and theletter "B" means belted-bias ply con-
struction.
5. Maximum permissible inflationpressure
This number is the greatest amount of air pressure that should be put in
the tire. Do not exceed the maximum
permissible inflation pressure. Refer
to the Tire and Loading Information
label for recommended inflation
pressure.
6. Maximum load rating
This number indicates the maximum
load in kilograms and pounds that
can be carried by the tire. When
replacing the tires on the vehicle,
always use a tire that has the same
load rating as the factory installed
tire.
7. Uniform tire quality grading
Quality grades can be found where
applicable on the tire sidewall
between tread shoulder and maxi-
mum section width.
For example:
TREADWEAR 200
TRACTION AA
TEMPERATURE A
Tread wear
The tread wear grade is a compara-
tive rating based on the wear rate ofthe tire when tested under controlled
conditions on a specified govern-
ment test course. For example, a tire
graded 150 would wear one-and-a-
half times (1½) as well on the gov-
ernment 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.WARNING - Tire age
Tires degrade over time, even
when they are not being used.
Regardless of the remaining
tread, we recommend that tires
generally be replaced after six
(6) years of normal service.
Heat caused by not climates orfrequent high loading condi-
tions can accelerate the aging
process. Failure to follow this
Warning can result in sudden
tire failure, which could lead to
a loss of control and an acci-
dent involving serious injury ordeath.
