Tire Labeling; Sizes - SMART fortwo coupe Operator's Manual

For example, a tire graded 150 would wear
1
one and one-half (1
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
G
Warning!
The traction grade assigned to this tire is
based on straight-ahead braking traction
tests, and does not include acceleration,
cornering, hydroplaning, or peak traction
characteristics.
The traction grades, from highest to
lowest, are AA, A, B, and C. Those grades
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.
Temperature
G
Warning!
The temperature grade for this tire is
established for a tire that is properly
inflated and not overloaded. Excessive
speed, underinflation, or excessive
loading, either separately or in
combination, can cause excessive heat
build-up and possible tire failure.
The temperature grades are A (the highest),
B, and C, representing the tire's resistance
to the generation of heat and its ability to
dissipate heat when tested under
controlled conditions on a specified
indoor laboratory test wheel. Sustained
high temperature can cause the material of
the tire to degenerate and reduce tire life,
and excessive temperature can lead to
/ ) times as well on the
2
sudden tire failure. The grade C
corresponds to a level of performance
which all passenger car tires must meet
under the Federal Motor Vehicle Safety
Standard No. 109. Grades B and A represent
higher levels of performance on the
laboratory test wheel than the minimum
required by law.
Rotating tires
G
Warning!
Do not rotate front and rear wheels as they
have different dimensions, e.g. rim size,
wheel offset etc. Otherwise, the handling
can be affected and you could endanger
yourself and others.
Thoroughly clean the mounting face of the
wheels and brake discs, i.e. the inner side
of the wheels/tires each time the wheels/
tires are changed. Check for and ensure
proper tire inflation pressure.
G
Warning!
Have the tightening torque checked after
changing a wheel. Wheels could become
loose if not tightened with a torque of
81 lb‑ft (110 Nm).
Only use genuine smart wheel bolts
specified for your vehicle's rims.
For information on wheel change, see "Flat
Y
tire" ( page 176).

Tire labeling

Besides tire name (sales designation) and
manufacturer name, a number of markings
can be found on a tire.
Following are some explanations for the
markings on your vehicle's tires:
Tires and wheels
129
Z