
 
Overall width 
Total width measured at the exterior sidewalls of an inflated tire, including the additional width of 
labeling, decorations, or protective bands or ribs. 
Passenger car tire 
A tire intended for use on passenger cars, multipurpose passenger vehicles, and trucks, that have a 
gross vehicle weight rating (GVWR) of 10,000 pounds or less. 
Ply 
A layer of rubber-coated parallel cords. 
Ply separation 
A parting of rubber compound between adjacent plies. 
Pneumatic tire 
A mechanical device made of rubber, chemicals, fabric, and steel or other materials, that, when 
mounted on an automotive wheel, provides the traction and contains the gas or fluid that sustains the 
load. 
Production options weight 
The combined weight of installed regular production options weighing over 5 lbs (2.3 kg) more then the 
standard items they replace, and not previously considered as curb weight or accessory weight. These 
include, for example, heavy-duty brakes, ride levelers, heavy-duty battery, and special trim. 
Radial ply tires 
A pneumatic tire in which the ply cords that extend to the beads are laid at substantially 90 degrees to 
the centerline of the tread. 
Recommended inflation pressure 
The tire pressure recommended by the vehicle manufacturer for a tire of a specified size that has not 
been driven for more than a couple of miles (kilometers) at low speeds in the 3 hour period before the 
tire pressure is measured or adjusted. 
Reinforced tire 
A tire designed to operate at higher loads and at higher inflation pressures than the corresponding 
standard tire. 
Rim 
The outer edge of a wheel upon which the tire beads are seated. 
Rim diameter 
The nominal diameter of the wheel's tire bead seating surface. If you change your wheel size, to 
wheels of a different diameter, you will have to purchase new tires to match the new wheels. 
Rim size 
Designation means rim diameter and width. 
Rim type designation 
The industry or manufacturer's designation for a rim by style or code. 
Rim width 
The nominal distance between wheel rim flanges.  

 
Section width 
The linear distance between the exteriors of the sidewalls of an inflated tire, excluding elevations due 
to labeling decoration, or protective bands. 
Sidewall 
The portion of a tire between the bead and the tread. 
Sidewall separation 
The parting of the rubber compound from the cord material in the sidewall. 
Speed rating (letter code) 
A standardized letter code indicating the maximum speed at which a tire is designed to be driven for 
extended periods of time. The ratings range from 93 mph or 150 km/h (“P”) to 186 mph or (300 km/h) 
“Y”. 
The speed rating letter code, where applicable, is molded on the tire sidewall. You may not find this 
information on all tires because it is not required by law. 
Tire Pressure Monitoring System 
A system that detects when at least one of a vehicle's tires is underinflated and illuminates a low tire-
pressure warning light. 
Tread 
The portion of a tire that normally touches the road. 
Tread rib 
A tread section running circumferentially around a tire. 
Tread separation 
Tire failure caused by the tread pulling away from the tire carcass. 
Tread wear indicators (TWI) 
Raised areas within the main tread grooves that show, visually, when tires are worn and near the end 
of their useful life. 
Uniform Tire Quality Grading (UTQG) 
A tire information system developed by the U.S. National Highway Traffic Safety Administration 
(NHTSA) that is designed to help buyers compare tires. UTQG is not a safety rating, nor is it a 
guarantee that a tire will last for a certain number of miles or perform a certain way. It gives tire buyers 
more information to compare with factors such as price, brand loyalty and dealer recommendations. 
Under UTQG, tires are graded by the tire manufacturers in 3 areas: tread wear, traction and 
temperature resistance. UTQG information is molded into the tire sidewalls. 
U.S. DOT Tire Identification Number (TIN) 
A tire's serial number. It begins with the letters “DOT” (“Department of Transportation”) and indicates 
that the tire meets all federal standards. The next two numbers or letters indicate the plant where the 
tire was manufactured. The last four numbers represent the week and year of manufacture. 
For example, the numbers 1709 mean that the tire was produced in the 17th week of 2009. Any other 
numbers are marketing codes used by the tire manufacturer. This information is used to help identify 
affected consumers if a tire defect requires a recall. 
Vehicle capacity weight 
The total rated cargo, luggage and passenger load. Passenger load is 150 lbs (68 kilograms) times the 
vehicle's total seating capacity (as listed on the label inside the driver door).  

 
Vehicle maximum load on the tire 
The load on an individual tire that is determined by taking each axle's share of the maximum loaded 
vehicle weight (GAWR) and dividing by 2. 
Vehicle normal load on the tire 
The load on an individual tire that is determined by taking each axle's share of the curb weight, 
accessory weight, and normal occupant weight (distributed according to the table below) and dividing 
by 2. 
Wheel size designation 
Wheel rim diameter and width. 
Occupant loading and distribution for vehicle normal load for various designated seating 
capacities 
 
Designated seating capacity, 
number of occupants 
Vehicle normal load, number 
of occupants 
Occupant distribution in a 
normally loaded vehicle 
2, 3 or 4  2  2 in front 
5  3  2 in front, 1 in back 
 
Applicable only in Mexico, the AGCC, and South Korea 
Glossary of tire and loading terminology 
 

 
Cord separation 
The parting of cords from adjacent rubber compounds. 
Cracking 
Any parting within the tread, sidewall, or inner liner of the tire extending to cord material. 
Cold tire inflation pressure 
The tire pressure recommended by the vehicle manufacturer for a tire of a specified size that has not 
been driven for more than a couple of miles (kilometers) at low speeds in the 3 hour period before the 
tire pressure is measured or adjusted. 
Curb weight 
The weight of a motor vehicle with standard equipment including the maximum capacity of fuel, oil, 
and coolant, air conditioner, and additional weight of optional equipment. 
Extra load tire 
A tire designed to operate at higher loads and at higher inflation pressures than the corresponding 
standard tire. 
Gross Axle Weight Rating (GAWR) 
The load-carrying capacity of a single axle system, measured where the tire contacts the ground. 
Gross Vehicle Weight Rating (GVWR) 
The maximum loaded weight of the vehicle. 
Groove 
The space between 2 adjacent tread ribs. 
Load rating (code) 
The maximum load that a tire is rated to carry for a given inflation pressure. You may not find this 
information on all tires because it is not required by law. 
Maximum load rating 
The load rating for a tire at the maximum permissible inflation pressure for that tire. 
Maximum loaded vehicle weight 
The total of: 
 x Curb weight 
 x Accessory weight. 
 x Vehicle capacity weight. 
 x Production options weight. 
Maximum (permissible) inflation pressure 
The maximum cold inflation pressure to which a tire may be inflated. Also called “maximum inflation 
pressure.” 
Normal occupant weight 
Means 150 lbs (68 kilograms) times the number of occupants seated in the vehicle up to the total 
seating capacity of your vehicle. 
Occupant distribution 
The placement of passengers in a vehicle.  

 
Outer diameter 
The diameter of a new, properly inflated tire. 
Overall width 
Total width measured at the exterior sidewalls of an inflated tire, including the additional width of 
labeling, decorations, or protective bands or ribs. 
Passenger car tire 
A tire intended for use on passenger cars, multipurpose passenger vehicles, and trucks, that have a 
gross vehicle weight rating (GVWR) of 10,000 pounds or less. 
Ply 
A layer of rubber-coated parallel cords. 
Ply separation 
A parting of rubber compound between adjacent plies. 
Pneumatic tire 
A mechanical device made of rubber, chemicals, fabric, and steel or other materials, that, when 
mounted on an automotive wheel, provides the traction and contains the gas or fluid that sustains the 
load. 
Production options weight 
The combined weight of installed regular production options weighing over 5 lbs (2.3 kg) more then the 
standard items they replace, and not previously considered as curb weight or accessory weight. These 
include, for example, heavy-duty brakes, ride levelers, heavy-duty battery, and special trim. 
Radial ply tires 
A pneumatic tire in which the ply cords that extend to the beads are laid at substantially 90 degrees to 
the centerline of the tread. 
Recommended inflation pressure 
The tire pressure recommended by the vehicle manufacturer for a tire of a specified size that has not 
been driven for more than a couple of miles (kilometers) at low speeds in the 3 hour period before the 
tire pressure is measured or adjusted. 
Reinforced tire 
A tire designed to operate at higher loads and at higher inflation pressures than the corresponding 
standard tire. 
Rim 
The outer edge of a wheel upon which the tire beads are seated. 
Rim diameter 
The nominal diameter of the wheel's tire bead seating surface. If you change your wheel size, to 
wheels of a different diameter, you will have to purchase new tires to match the new wheels. 
Rim size 
Designation means rim diameter and width. 
Rim type designation 
The industry or manufacturer's designation for a rim by style or code. 
Rim width 
The nominal distance between wheel rim flanges.  

 
Section width 
The linear distance between the exteriors of the sidewalls of an inflated tire, excluding elevations due 
to labeling decoration, or protective bands. 
Sidewall 
The portion of a tire between the bead and the tread. 
Sidewall separation 
The parting of the rubber compound from the cord material in the sidewall. 
Speed rating (letter code) 
A standardized letter code indicating the maximum speed at which a tire is designed to be driven for 
extended periods of time. The ratings range from 93 mph or 150 km/h (“P”) to 186 mph or (300 km/h) 
“Y”. 
The speed rating letter code, where applicable, is molded on the tire sidewall. You may not find this 
information on all tires because it is not required by law. 
Tire Pressure Monitoring System 
A system that detects when at least one of a vehicle's tires is underinflated and illuminates a low tire-
pressure warning light. 
Tread 
The portion of a tire that normally touches the road. 
Tread rib 
A tread section running circumferentially around a tire. 
Tread separation 
Tire failure caused by the tread pulling away from the tire carcass. 
Tread wear indicators (TWI) 
Raised areas within the main tread grooves that show, visually, when tires are worn and near the end 
of their useful life. 
Uniform Tire Quality Grading (UTQG) 
A tire information system developed by the U.S. National Highway Traffic Safety Administration 
(NHTSA) that is designed to help buyers compare tires. UTQG is not a safety rating, nor is it a 
guarantee that a tire will last for a certain number of miles or perform a certain way. It gives tire buyers 
more information to compare with factors such as price, brand loyalty and dealer recommendations. 
Under UTQG, tires are graded by the tire manufacturers in 3 areas: tread wear, traction and 
temperature resistance. UTQG information is molded into the tire sidewalls. 
U.S. DOT Tire Identification Number (TIN) 
A tire's serial number. It begins with the letters “DOT” (“Department of Transportation”) and indicates 
that the tire meets all federal standards. The next two numbers or letters indicate the plant where the 
tire was manufactured. The last four numbers represent the week and year of manufacture. 
For example, the numbers 1709 mean that the tire was produced in the 17th week of 2009. Any other 
numbers are marketing codes used by the tire manufacturer. This information is used to help identify 
affected consumers if a tire defect requires a recall. 
Vehicle capacity weight 
The total rated cargo, luggage and passenger load. Passenger load is 150 lbs (68 kilograms) times the 
vehicle's total seating capacity (as listed on the label inside the driver door).  

 
Vehicle maximum load on the tire 
The load on an individual tire that is determined by taking each axle's share of the maximum loaded 
vehicle weight (GAWR) and dividing by 2. 
Vehicle normal load on the tire 
The load on an individual tire that is determined by taking each axle's share of the curb weight, 
accessory weight, and normal occupant weight (distributed according to the table below) and dividing 
by 2. 
Wheel size designation 
Wheel rim diameter and width. 
Occupant loading and distribution for vehicle normal load for various designated seating 
capacities 
 
Designated seating capacity, 
number of occupants 
Vehicle normal load, number 
of occupants 
Occupant distribution in a 
normally loaded vehicle 
2, 3 or 4  2  2 in front 
5  3  2 in front, 1 in back 
 
Applicable only in the United States and Canada 
Tires and vehicle load limits