DOT Tire Quality Grading
The tires on your vehicle meet all U.S. Federal Safety Requirements. All tires
are also graded for treadwear, traction, and temperature performance
according to Department of Transportation (DOT) standards. These gradings
are explained below.
n
Uniform Tire Quality Grading
Quality grades can be found where applicable on the tire sidewall between
tread shoulder and maximum section width.
For example:
Treadwear 200
Traction AA
Temperature A
All passenger car tires must conform to Federal Safety Requirements in
addition to these grades.
n
Treadwear
The treadwear grade is a comparative rating based on the wear rate of the
tire when tested under controlled conditions on a specified government
test course. For example, a tire graded 150 would wear one and one-half (1
1/2) times as well on the 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.
n
Traction
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.
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.
n
Temperature
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
MAINTENANCE
150 |
to degenerate and reduce tire life, and excessive temperature can lead to
sudden tire failure. The grade C corresponds to a level of performance
which all passenger car tire 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.
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 heat buildup and possible tire failure.
Air Conditioning
To ensure proper and safe operation, the Society of Automotive Engineers
(SAEJ2845) recommends that the refrigerant system only be serviced by
trained and certified technicians.
Never repair or replace the air conditioning evaporator (cooling coil) with one
removed from a used or salvaged vehicle.
New replacement mobile air conditioning evaporators must be certified (and
labeled) as meeting SAE Standard J2842.
Testing of Readiness Codes
Your vehicle has readiness codes as part of the onboard self-diagnostic
system. Some states use these codes for testing to verify whether your
vehicle’s emissions components are working properly. The codes may not be
read if you go through the testing just after the battery has gone dead or been
disconnected.
To check if they are set, set the power mode to ON without starting the
engine. The malfunction indicator lamp will come on for several seconds. If it
goes off, the readiness codes are set. If it blinks five times, the readiness codes
are not set.
If you are required to have your vehicle tested before the readiness codes are
set, prepare the vehicle for retesting by doing the following:
1. Fill the gas tank to approximately 3/4 full.
2. Park the vehicle and leave the engine off for 6 hours or more.
3. Make sure the ambient temperature is between 40°F and 95°F (4°C and
35°C).
4. Start the engine without touching the accelerator pedal, and let it idle for
20 seconds.
5. Keep the vehicle in PARK (P). Increase the engine speed to 2,000 rpm, and
hold it there for about 3 minutes.
MAINTENANCE
| 151
