7-56
Maintenance
4. Tyre ply composition and
material
The number of layers or plies of rub-
ber-coated fabric in the tyre. Tyre
manufacturers also must indicate the
materials in the tyre, 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 the
letter "B" means restrained-bias ply
construction.
5. Maximum permissible infla-
tion pressure
This number is the greatest amount
of air pressure that should be put in
the tyre. Do not exceed the maximum
permissible inflation pressure. Refer
to the Tyre 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 tyre. When
replacing the tyres on the vehicle,
always use a tyre that has the same
load rating as the factory installed
tyre.
7. Uniform tyre quality grading
Quality grades can be found where
applicable on the tyre sidewall
between tread shoulder and maxi-
mum section width.
For example:
TREAD WEAR 200
TRACTION AA
TEMPERATURE A
Tread wear
The tread wear grade is a compara-
tive rating based on the wear rate of
the tyre when tested under controlled
conditions on a specified government
test course. For example, a tyre grad-
ed 150 would wear one-and-a-half
times (1½) as well on the government
course as a tyre graded 100.The relative performance of tyres
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.
These grades are molded on the
sidewalls of passenger vehicle tyres.
The tyres available as standard or
optional equipment on your vehicle
may vary with respect to grade.
Traction - AA, A, B & C
The traction grades, from highest to
lowest, are AA, A, B and C. Those
grades represent the tyre’s ability to
stop on wet pavement as measured
under controlled conditions on speci-
fied government test surfaces of
asphalt and concrete. A tyre marked C
may have poor traction performance.
