![UTQG ratings on Japanese Tire](https://upload.wikimedia.org/wikipedia/commons/9/93/UTQG_ratings_on_Japanese_Tire.jpg)
Uniform Tire Quality Grading, commonly abbreviated as UTQG, is the term encompassing a set of standards for passenger car
tire
A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...
s that measures a tire's
treadwear,
temperature resistance and
traction. The UTQG was created by the
National Highway Traffic Safety Administration
The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rela ...
in 1978, a branch of the
United States Department of Transportation
The United States Department of Transportation (USDOT or DOT) is one of the executive departments of the U.S. federal government. It is headed by the secretary of transportation, who reports directly to the President of the United States and ...
(DOT). All tires manufactured for sale in the United States since March 31, 1979 are federally mandated to have the UTQG ratings on their sidewall as part of the DOT approval process, in which non-DOT approved tires are not legal for street use in the United States.
It is not to be confused with the
tire code
Automotive tires are described by an alphanumeric tire code (in North American English) or tyre code (in Commonwealth English), which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some o ...
, a supplemental and global standard measuring tire dimensions, load-bearing ability and maximum speed, maintained by tire industry trade organizations and the
International Organization for Standardization
The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...
.
The
National Highway Traffic Safety Administration
The National Highway Traffic Safety Administration (NHTSA ) is an agency of the U.S. federal government, part of the Department of Transportation. It describes its mission as "Save lives, prevent injuries, reduce vehicle-related crashes" rela ...
(NHTSA) established the Uniform Tire Quality Grading Standards (UTQGS) in 49 CFR 575.104.
When looking at UTQG ratings it is important to realize that the Department of Transportation does not conduct the tests. The grades are assigned by the tire manufacturers based on their test results or those conducted by an independent testing company they have hired. The NHTSA has the right to inspect tire manufacturers' data, and can fine them if inconsistencies are found.
The NHTSA published DOT HS 812 325 “Consumer Guide to Uniform Tire Quality Grading” August 2016, which provides rating information.
Dedicated winter tires, also known as snow tires, are not required to have a UTQG rating.
Non-passenger car tires, such as those for
motorcycle
A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...
s,
bus
A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...
es,
medium trucks and above along with
trailers are also not required to have a UTQG rating, although
FMVSS
The Federal Motor Vehicle Safety Standards (FMVSS) are U.S. federal vehicle regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated automobile safety-related components, systems, and d ...
Standard 109 requires the following to be listed on the tire's sidewall: speed restriction if less than 55 mph, regroovable if designed for regrooving, and a letter designating load range rating.
Components
The UTQG rating is made up of three components, treadwear, traction and temperature.
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 track. A tire graded 200 would last twice the distance on the government test course under specified test conditions as one graded 100. In theory, this means that a tire with a 200 grade will wear twice the distance as a tire with a 100 grade. However, tire manufacturers are not under any obligation to grade a tire based on the test results, except to say that they cannot overstate the grade. This is enforced by NHTSA requiring documentation to justify any assignment of a grade on a tire, "These treadwear grades are no guarantee of actual tire mileage; differences in driving habits, service practices, climate, and road characteristics will affect a tire's longevity."
As Course Monitoring Tires have changed, their treadwear grades have changed to numbers considerably higher than 100. As a result, it would be incorrect to say that a tire with a treadwear grade of 200 gets twice the life of the Course Monitoring Tire.
Methodology
The wear on tires that are being tested ("candidate tires") is compared to the wear of Course Monitoring Tires (CMT), which are sold by the NHTSA at its UTQG test facility in
San Angelo, Texas
San Angelo ( ) is a city in and the county seat of Tom Green County, Texas, United States. Its location is in the Concho Valley, a region of West Texas between the Permian Basin to the northwest, Chihuahuan Desert to the southwest, Osage Plai ...
. Both types of tires are mounted on vehicles that will be driven in a
convoy
A convoy is a group of vehicles, typically motor vehicles or ships, traveling together for mutual support and protection. Often, a convoy is organized with armed defensive support and can help maintain cohesion within a unit. It may also be used ...
during the test, thus ensuring that the candidate tires and the CMT tires experience the same road conditions. The convoy, typically comprising four or fewer vehicles, will drive 7200 miles on
public roads
A highway is any public or private road or other public way on land. It is used for major roads, but also includes other public roads and public tracks. In some areas of the United States, it is used as an equivalent term to controlled-access ...
in
West Texas
West Texas is a loosely defined region in the U.S. state of Texas, generally encompassing the arid and semiarid lands west of a line drawn between the cities of Wichita Falls, Abilene, and Del Rio.
No consensus exists on the boundary betwee ...
. Candidate tire wear will be checked during and after the test, and compared to the wear on the CMT tires from the same convoy.
The first CMTs were commercially-available Goodyear Custom Steelguards, and
Goodyear Tire and Rubber Company
The Goodyear Tire & Rubber Company is an American multinational tire manufacturing company founded in 1898 by Frank Seiberling and based in Akron, Ohio. Goodyear manufactures tires for automobiles, commercial trucks, light trucks, motorcycles, S ...
produced all CMT tires from 1975 until 1984. From 1984 to 1991, the CMT tires were produced by
Uniroyal
The company formerly known as the United States Rubber Company, now Uniroyal, is an American manufacturer of tires and other synthetic rubber-related products, as well as variety of items for military use, such as ammunition, explosives, chemi ...
. CMT tires are now "specially designed and built to
American Society for Testing and Materials (ASTM) standard E1136 to have particularly narrow limits of variability.
1
Relation to friction coefficient
A study has shown a statistical relationship between the average
friction coefficient
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of t ...
(µ) and the treadwear rating of tires tested.
This relationship can be represented by the following formula:
:
Generally speaking, a lower treadwear rating correlates with a higher friction coefficient and thus provides a shorter
braking distance
Braking distance refers to the distance a vehicle will travel from the point when its brakes are fully applied to when it comes to a complete stop. It is primarily affected by the original speed of the vehicle and the coefficient of friction be ...
. A softer, more sticky tire, wears off its material faster to provide this performance.
However, this is an average rule, and for the same friction coefficient, the curve in this study shows large variations in treadwear rating, which decrease the significance of this relationship. Thus, depending on production method and tire model, the quality of rubber (thanks to certain additives) can multiply the treadwear rating by more than 3 without lessening the friction coefficient.
Limitations
The treadwear grade is a ratio and not a mileage. This is because multiple factors determine treadwear rates and most of them are a function of driving conditions and operating environment, and not the tire itself. As a result, actual tire wear will vary considerably within the same tire line. However, two tires with exactly the same compound should have a treadwear rating that varies in accordance with tread depth.
The assigning of UTQG grades is done solely by the tire manufacturer. In many cases, this has resulted in the UTQG grading system to be more of a marketing tool than was originally intended.
It is legal and permissible for a tire manufacturer to give a particular tire line a lower treadwear grade. For example, if the highest treadwear grade in a manufacturer's lineup is 600, then a tire line with a lower treadwear test result might receive a grade of 400, instead of the 480 it could possibly receive.
Also, it is common for tires whose treadwear grade is of little commercial value, such as racing tires, to be assigned extremely low values - sometimes even zero.
Traction
Traction grades, from highest to lowest, are AA, A, B and C. 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 testing does not take into account cornering, hydroplaning, acceleration or stopping on a dry surface. Nor does it account for the significantly different effectiveness of ABS versus non-ABS braking systems on a tire's stopping distance.
The UTQGS traction test procedure measures a tire's coefficient of friction when it is tested on wet asphalt and concrete surfaces. The test tire is installed on an instrumented axle of a traction trailer, which is towed by a truck at 40 miles per hour (mph) over wet asphalt and concrete surfaces. The tow truck is equipped with an on-board water supply system that sprays water in front of the test tire. The brakes, from the test tire only, are momentarily locked, and sensors on the axle measure the longitudinal and vertical forces as it slides in a straight line. The coefficient of friction for the pair, test tire and surface, is then determined as the ratio of the longitudinal and vertical forces.
The UTQGS traction rating procedure specifies that the traction coefficients for asphalt and for concrete are to be calculated using the locked-wheel traction coefficient on the tire, or sliding coefficient of friction. More specifically, upon application of the brakes, the tire is subjected to shear between the wheel and the road surface, and deforms towards the rear of the vehicle. This generates a traction force to oppose the motion of the vehicle. As braking torque increases, the tire deforms more and tread elements near the rear of the contact patch with the road begin to slip rather than grip. The coefficient of friction rapidly reaches a maximum value at about 10-20 percent slip, and then declines as the longitudinal slip values increase to 100 percent, which represents a fully locked tire. The maximum coefficient of friction in the 0-100 percent slip range is termed "peak" coefficient of friction, and the lower coefficient value for the fully locked tire is termed "slide" coefficient of friction.
Temperature
The temperature grades, from highest to lowest, are A, B and C. These represent the tire's resistance to the generation of heat at speed. Tires graded A effectively dissipate heat up to a maximum speed that is greater than 115 mph. B rates at a maximum between 100 mph and 115 mph. C rates at a maximum of between 85 mph to 100 mph. Tires that cannot grade up to C or higher cannot be sold in the US.
See also
*
Tire code
Automotive tires are described by an alphanumeric tire code (in North American English) or tyre code (in Commonwealth English), which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some o ...
*
Wheel sizing
The wheel size for a motor vehicle or similar wheel has a number of parameters.
Units
The millimetre is most commonly used to specify dimensions in modern production, but marketing of wheel sizes towards customers is still sometimes done with tr ...
*
European Tyre and Rim Technical Organisation The European Tyre and Rim Technical Organisation (ETRTO) exists to specify and harmonise sizes of rims and their associated pneumatic tyres across the European Union. ETRTO sizes apply to rims and tyres for vehicles of all types, including bicycles ...
References
External links
Tire Safety brochureby the NHTSA
SaferCar.gov- U.S. Government service to look up treadwear grades on different type of tires.
{{Tires, state=collapsed
Tires
Standards of the United States
1978 in American law
1979 introductions
Automotive safety