Choosing the right tire
Before deciding which replacement tires to use on your vehicle, consult the manufacturers information usually found on the doorframe, door edge, and the glove compartment door or check the owner’s manual for the original size and recommended air pressure.
A. Load Rating
The load carrying capacity of the replacement tires must always equal or exceed the load carrying capacity of the original equipment tires. Refer to the tire placard on the vehicle for the recommended operating pressures of the original equipment size tires. Do not exceed the maximum pressure indicated on the tire sidewall. Tires that are loaded beyond their maximum allowable loads will build up excessive heat that may result in sudden tire destruction. Follow the manufactures instructions on the vehicle placard or the owner’s manual regarding the maximum allowable gross axle weight rating. DO NOT EXCEED THE WEIGHT RATING CAPACITY OF THE VEHICLE. Overloading a vehicle can cause the tires to overheat which can also cause the destruction of the tire.
Light truck tires use a letter designation to indicate load range, ply rating and maximum load pressure (PSI). Refer to the following chart for these capacities:
Load Range | Ply Rating | Maximum Load Pressure |
Standard | — | 35 |
Extra Load | — | 41 |
B | 4 | 35 |
C | 6 | 50 |
D | 8 | 65 |
E | 10 | 80 |
F | 12 | 95 |
The light truck tires ply rating or load range does not indicate the actual number of layers of ply material in the tire, but gives the equivalent strength of the tire construction.
B. DOT Quality Grades
The federal Government Uniform Tire Quality Grading Standard applies to passenger tires only (but excludes deep tread, winter type snow tires, temporary use spare tires, and tires with nominal rim diameters of twelve inches or less). Tires subject to the standard are required to be graded on the performance factors of treadwear, traction, and temperature. The grades are molded on the tire sidewall, and, in addition for replacement tires, a label affixed to the tread lists and explains these grades.
TREADWEAR | 000 |
TRACTION | A B C |
TEMPERATURE | A B C |
Treadwear – All passenger car tires must conform to Federal Safety Requirements in addition to these grades.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 a half 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.
Traction – 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. A tire marked C may have poor traction performance. WARNING: The traction grade assigned to this tire is based on braking (straight ahead) traction test and does not include cornering (turning traction).
Temperature – the temperature grades are A (highest), B, and C, representing the tire’s resistance to the generation of heat and it’s ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. Sustained High temperatures can cause the material of the tire to degenerate and reduce tire life, and excessive temperatures can lead to sudden tire failure. The 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 A and B 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, under inflation, or excessive loading, either separately or in combination, can cause heat buildup and possible tire failure.
C. Speed Capability
The speed capability of the replacement tires must always equal or exceed the original equipment tires.
When replacing tires, consult the placard (normally located on a door frame, door edge, or glove box door) or the owner’s manual for correct size. If the tires shown on the vehicle placard do not have speed ratings, the appropriate size tire with any speed rating may be applied.
When the placard tire size contains a speed symbol, for example P235/60HR16 or P235/60R16 90H, the replacement tire must have the same or higher speed rating symbol if the speed capability of the vehicle is to be maintained. If the replacement tire is not speed rated, the speed capability of the vehicle is limited by the speed capability of the replacement tire.
Speed | Category |
S | 180 km/h (112 mph) |
T | 190 km/h (118 mph) |
U | 200 km/h (124 mph) |
H | 210 km/h (130 mph) |
V | 240 km/h (149 mph) |
W | 270 km/h (168 mph) |
Y | 300 km/h (186 mph) |
D. Tire Size Designations
Size designations usually include letters, as well as numbers, which have the following meanings:
| R | Radial Construction |
| B | Belted Bias Construction |
| D | Bias Ply (Diagonal) Construction |
| P | Passenger Car |
| T | Temporary Spare |
| LT | Light Truck |
The speed rating symbol can be included as part of the tire size designation. For example the tire size P235/60HR16 has the following meaning:
P – Passenger car tire
235 – Nominal section width in millimeters
60 – Nominal aspect ratio (section height-to-width ratio)
H – H speed rated tire (130 mph maximum speed rating)
R – Radial tire construction
16 – Nominal rim diameter in inches