398
Operation
Tires and wheels
4
Tire load rating
Numerical code associated with the
maximum load a tire can support.
Tire ply composition and material
used
This indicates the number of plies or the
number of layers of rubber-coated fabric
in the tire tread and side wall. Tire man-
ufacturers also must indicate the ply ma-
terials in the tire and side wall, which
include steel, nylon, polyester, and oth-
ers.
Tire speed rating
Part of tire designation; indicates the
speed range for which a tire is approved.
Traction
Force exerted by the vehicle on the road
via the tires. The amount of grip provid-
ed.
Tread
The portion of a tire that comes into con-
tact with the road.
Treadwear Indicators
Narrow bands, sometimes called
“wear bars” that show across the tread
of a tire when only
1
/
16
in (1.6 mm) of
tread remains.
TWR (Tongue Weight Rating)
Maximum permissible weight on the
trailer tongue.
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