What is UTQG?
Tires have many markings on the sidewall, but most people don't understand the technical meaning of them, especially UTQG. Therefore, this time we would like to talk about UTQG.
UTQG stands for "Uniform Tire Quality Grading", which is required by "FMVSS" (FEDERAL MOTOR VEHICLE SAFETY STANDARDS) of the U.S. Department of Transportation. This standard requires motor vehicle and tire manufacturers and tire brand name owners to provide information indicating the relative performance of passenger car tires used in the U.S.A. in the area of Treadwear, Traction, and Temperature Resistance. This applies to all passenger car tires, except deep tread, winter-type snow tires, space-saver or temporary use spares, or tires with nominal rim diameters of twelve (12) inches or less. This is the standard with a history which had been judged as final in the Supreme Court of U.S.A. between the governments, vehicle manufacturers and tire manufacturers.
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 *. The grading fixes 30,000 miles (48,279kms) as 100% Index, and the grading shall be in multiplies of 20.
*The test course consists of three loops of a total of 400 miles (644kms) in the geographical vicinity of Goodfellow Air Force Base (AFB), San Angelo, Texas, U.S.A.
* Run a car with test tires mounted till 6,400 miles (10,300kms) pass.
(The tire is tested in convoy with a "base" tire so as to eliminate the variable of temperature and road surface.)
* Measure the tread depth after each 800 miles (1287kms) run.
* Then the projected worn out tire life is calculated. Fixing that 30,000 miles (48,279kms) as 100% Index.
For example, a tire graded 200 would wear twice 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 climates.
The traction grades, from highest to lowest, are A,B and C, and they represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete.
The tire to be tested is inflated to 24psi (165KPa) and installed on the test apparatus (instrumented trailer). The tire is loaded to 1,085 pounds (492kg). The trailer is towed over the wetted test area at 40mph (65km/h) and the rotating wheel is locked. The tire is dragged in this locked condition through the test area and the friction created is measured.
From these measurements the friction efficiency index of a tire can be calculated using the following formula.
U : Friction Efficiency Index
T : Pulling Power
F : Load
The temperature grades are A (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 a tire to degenerate and reduce tire life, and excessive temperature can lead to dangerous sudden failure. There 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 in the laboratory test than the minimum required by law in the U.S.A.
The temperature grade is established for a tire that is properly inflated and not overloaded.
THE CONDITION OF UTQG TEMPERATURE TEST
STEP SPEED TEST TIME (min) UTQG GRADING
1 50 80 60 :
2 75 120 30 :
3 80 128 30 :
4 85 136 30 C
5 90 144 30 :
6 95 152 30 :
7 100 160 30 v
8 105 168 30 :
9 110 176 30 B
10 115 184 30 v
11 120 192 30 :
12 125 200 30 :
13 130 208 30 A
14 135 216 30 :
15 140 224 30 :
16 145 232 30 v
A : Excellent | B : Good | C : Permissible
Recently not only in the U.S.A. but in many countries, customers are anxious to check the "UTQG" as one of their decision making factors in the selection of tires.
However, it is very important to know that the grades are obtained under controlled conditions, and are not completely applicable to actual usage.