The US Government has established the UTQG, the Uniform Tire Quality Grading, to
assist consumers in their purchase of tires. Basically it's another tool to be
used besides the opinions you gather from trusted friends, mechanics and
whatever other sources you may have at your disposal. The key to using this
system is to understand that it is a relative comparison system. The UTQG is not
a safety rating and not a guarantee that a tire will last for a prescribed
number of miles. Under UTQG, manufacturers use three criteria to grade tires:
treadwear, traction and temperature. The information is right where you need it
when buying the tire:
On the paper label affixed to the tread
On the tire molded into the sidewall
Treadwear Grade
The treadwear grade is a comparative rating based on the wear of a tire when
tested carefully under controlled conditions. For example the useful tread on a
tire graded 400 should last twice as long as a tire graded 200. However, another
tire manufacturer may grade a comparable design 300, so a grade of 150 would
last just half as long under their grading scheme. The lesson learned is to not
use one manufacturer's grade versus the other, but instead to compare tire
grades within a given brand. Actual treadwear performance can vary tremendously
according to the tire's real-world use. Variations in driving habits, service
practices (most importantly air pressure maintenance), road conditions and
climate affect tire life.
Traction Grades
Traction grades represent the tire's ability to stop on wet pavement as
measured under controlled conditions on asphalt and concrete test surfaces. As
of 1997, the traction grades from highest to lowest are "AA","A","B" and "C". A
tire graded "AA" may have relatively better traction performance than a tire
graded lower, based on straight-ahead braking tests. The grades do not take into
consideration the cornering or turning performance of a tire.
Temperature Grades
Temperature grades represent a tire's resistance to heat and its ability to
dissipate heat when tested under controlled laboratory test conditions. The
grades from highest to lowest are "A","B" and "C". The grade "C" corresponds to
the minimum performance required by federal safety standard. Therefore, the "A"
tire is the coolest running, and even though the "C" tire runs hotter it does
not mean it is unsafe. The temperature grade is established for a tire that is
properly inflated and not overloaded.
