This section provides an understanding of the many factors essential to proper tyre care and service of vehicles.
Information displayed on the tyre sidewall
Your tyre has very useful information molded into the sidewall. It shows the name of the tyre , its size, whether it is tubeless or tube type, the maximum load and maximum inflation, the important safety warning and much other information.
Shown on page 13 is the sidewall of a popular "P-metric," speed-rated auto tyre . "P" stands for passenger; "215" represents the width of the tyre in millimeters; "65" is the ratio of height to width; "R" means radial; "15" is the nominal rim diameter code; and "95H" is the optional service description that consists of the load index (95) and the speed symbol (H). Some older speed-rated tyres may include the speed symbol immediately before the "R" instead of showing a service description.
A "B" in place of the "R" means the tyre is belted bias construction. A "D" in place of the "R" means diagonal bias construction. "M+S" with the mountain/snowflake symbol is the designation that the tyre meets the RMA definitions for use in severe snow conditions. (See page 17).
The maximum load is shown in kg (kilograms) and in lbs (pounds), and maximum pressure in kPa (kilopascals) and in psi (pounds per square inch).
The letters "DOT" certify compliance with all applicable safety standards established by the Department of Transportation (DOT).
Adjacent to this is a tyre identification or serial number. This serial number is a code with up to 12 digits that are a combination of numbers and letters. The last characters are numbers identifying the week and year of manufacture. (Example: "1501" means fifteenth week of the year 2001.)
The sidewall also shows the type of cord and number of plies in the sidewall and under the tread.
The DOT requires tyre manufacturers to grade passenger car tyres based on three performance factors: treadwear, traction and temperature resistance.
The treadwear grade is a comparative rating based on the wear rate of the tyre when tested under controlled conditions on a specified government test track. A tyre graded 200 would wear twice as long on the government test course under specified test conditions as one graded 100. It is wrong to link treadwear grades with your projected tyre mileage. The relative performance of tyres depends upon the actual conditions of their use and may vary due to driving habits, service practices, differences in road characteristics and climate.
Traction grades, from highest to lowest, are AA, A, B and C. They represent the tyre 's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete.
The temperature grades, from highest to lowest, are A, B and C. These represent the tyre 's resistance to the generation of heat when tested under controlled conditions on a specified indoor laboratory test wheel.
Light Truck tyres
Shown below is typical information on the sidewall of a light truck tyre .
"LT" stands for Light Truck, "LT235/85R16" is the size designation for a metric light truck tyre .
"M+S" with the mountain/snowflake symbol is the designation that the tyre meets the RMA definition for use in severe snow conditions. (See page 17).
"LOAD RANGE D" identifies the load and inflation limits; RADIAL indicates that the tyre has a radial construction. "MAX LOAD SINGLE 1192 kg (2623 lbs) AT 1470 kPa (65 psi) COLD" indicates the maximum load rating of the tyre and corresponding minimum cold inflation pressure for that load when used as a single. For normal operation, follow pressure recommendations in owner's manual or on vehicle placard; "MAX LOAD DUAL 1082 kg (2381 lbs) AT 1470 kPa (65 psi) COLD" indicates the maximum load rating of the tyre and corresponding minimum cold inflation pressure when used in a dual configuration. The other markings on the sidewall have the same meaning as described for the passenger car tyre .
Check Tyre Pressures
Tyre Anantomy, Design and Construction
Replacement Tyre Selection
How Cold Temperature Affects Tyres
The Legal requirements for legal tyres on UK cars