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Wheel size designation
Wheels are also marked with important
information that you need if you ever
have to replace one. The following ex‐
plains what the letters and numbers in
the wheel size designation mean.
Example wheel size designation:
7.5JX18
7.5 - Rim width in inches.
J - Rim contour designation.
18 - Rim diameter in inches.
Tire speed ratings
The chart below lists many of the dif‐
ferent speed ratings currently being
used for passenger car tires. The speed
rating is part of the tire size designa‐
tion on the sidewall of the tire. This
symbol corresponds to that tire's de‐
signed maximum safe operating speed.
Speed
Rating
Symbol
Maximum Speed
S 180 km/h (112 mph)
T 190 km/h (118 mph)
H 210 km/h (130 mph)
V 240 km/h (149 mph)
Z
Above 240 km/h (149
mph)
3. Checking tire life (TIN: Tire
Identification Number)
Any tires that are over 6 years old,
based on the manufacturing date, (in‐
cluding the spare tire) should be re‐
placed by new ones. You can find the
manufacturing date on the tire sidewall
(possibly on the inside of the wheel),
displaying the DOT Code. The DOT Code
is a series of numbers on a tire consist‐
ing of numbers and English letters. The
manufacturing date is designated by
the last four digits (characters) of the
DOT code.
DOT : XXXX XXXX OOOO
The front part of the DOT means a
plant code number, tire size and tread
pattern and the last four numbers indi‐
cate week and year manufactured.
For example:
DOT XXXX XXXX 1617 represents that
the tire was produced in the 16th week
of 2017.
WARNING
n
Tire age
(Continued)
(Continued)
Tires degrade over time, even when
they ar
e not being used.
Regardless of the remaining tread, it
is recommended that tires generally
be replaced after six (6) years of
normal service. Heat caused by hot
climates or frequent high loading
conditions can accelerate the aging
process. Failure to follow this warn‐
ing can result in sudden tire failure,
which could lead to a loss of control
and an accident involving serious in‐
jury or death.
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 construction;
the letter "D" means diagonal or bias
ply construction; and the letter "B"
means belted-bias ply construction.
7-55
7
Maintenance
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