You might have seen a number of alphanumeric markings on the side of tires, have you ever thought what those markings mean? If your answer is “no”, don’t worry we will explain all those markings one by one in this article and it will help you in order to select a better tire for your Semi truck & trailer.
First of all, we can see that there are different types of marking on tires which can be broadly classified into 6 categories:
- Tire Width, Aspect Ratio, Construction Type, Rim Size, Load Index (Single / Double) & Speed Rating Marking
- DOT (Department of Transport) Safety Marking
- Max. Cold Inflation & Load Limit Marking
- Tire Ply Composition & Materials Used Marking
- Special Terrain Type Markings
- Tread-wear, Traction & Temperature Grades Marking
Now, we will discuss all these different categories of markings one by one in details.
Tire Width, Aspect Ratio, Construction Type, Rim Size, Load Index & Speed Rating Marking
With the following image we tried to explain all the important markings of tire in an easy to understand way.
We are taking an example of a tire, with marking as 295/75 R 22.5 144/141 L and will explain each part of this marking as follows:
- 295 – Here ‘295’ represents the section width of the tire in mm (millimetre)
- 75 – This ’75’ represents the aspect ratio of tire, which means tire’s section height to the tire’s section width in percentage (%), in easy words this 75 represents that tire’s section height is equal to 75% of tire’s section width.
*Note: Some Standard profile tires (for example 11R22.5 ) don’t have this aspect ratio mentioned, and in that case standard profile tires have aspect ratio of ’88’
- R – This character represents the construction type of tire, and ‘R’ here means ‘Radial’ tire.
- 22.5 – This represent Rim Diameter in inch, here ‘22.5’ means rim diameter of 22.5 inch
- 144/141 – These two numbers represents load index of the tire in both single and double tire configuration, ‘144’ represents load index for single tire configuration and ‘141’ represents load index for double tire configuration. For more details on how to determine the maximum load per tire in single & double tire configuration using load index table, click here…
- L – This character represents the Speed Rating of your tire, it is also called by the name ‘Speed Symbol‘.For more details on speed rating chart using which you can determine the maximum speed possible on your tire at its recommended load capacity, click here…
DOT (Department Of Transport) Marking
DOT markings are used to confirm that tire meets all the DOT standard for sale & use in Canada and the United States. We will explain all aspects of this marking with an example DOT CC9L XYZ1016:
- DOT – DOT here means ‘Department Of Transport’ and it represents that this tire meets all the requirements for the Department Of Transport and is eligible for sale & use in Canada and the United States.
- CC – This represents the plant code, and can be used to identify that at which DOT approved plant this tire has been manufactured, each DOT approved plant in the world have their own unique plant code provided by the DOT.
- 9L – This represent tire size, this is a unique alphanumeric code which is used by DOT to represents size of the tire, however we the normal users use tire width, aspect ratio & rim size markings to find out the tire size.
- XYZ – Brand characteristics, and these letters are used by DOT to represent the brand which has manufactured the tire.
- 10 – This represents the week of the year in which tire was manufactures, so ’10’ means it was manufactured in the 10th week of the year.
- 16 – Represents the year in which tire was manufactured, so ’16’ means it was manufactured in 2016, and 1016 collectively represents that particular tire was manufactured in the 10th week of 2016.
Max. Cold Inflation and Load Limit Marking
This marking is used to represent the maximum load of the tire and corresponding maximum cold inflation pressure for that load when used in a single or dual configuration. Sidewall markings are given in both metric and English units. Follow tire inflation pressure recommendations on the vehicle tire placard, certification label, or in the owner’s manual. Lets look at an example markings to understand them better as follows:
- Max Load Single 1597 kg (3520 lbs) at 550 kPa (80 psi) Max Pressure Cold – This means that tire can withstand maximum load of 1380 kg (3042 lbs) at max cold pressure of 550 kPA (80 psi) in single tire configuration.
- Max Load Dual 1360 kg (3000 lbs) at 550 kPa (80 psi) Max Pressure Cold – This means that tire can withstand maximum load of 1260 kg (2778 lbs) at max cold pressure of 550 kPA (80 psi) in double tire configuration.
Tire Ply Composition & Materials Used Marking
This marking indicates the number of plies (layers of rubber-coated fabric) in the tire tread and sidewall. Tire manufacturers also must indicate the ply materials in the tire and the sidewall, which include steel, nylon, polyester, and others.s. Lets take an example of following marking to understand it better:
- TREAD 10 PLIES: 6 Polyester + 4 Steel – This means the tread of the tire has 10 plies (10 layers of rubber-coated fabric) out of which 6 Plies are of Polyester and 4 Steel Plies.
- SIDEWALL 4 PLIES: 2 Polyester + 2 Steel – This means the sidewall of the tire has 4 plies (4 layers of rubber-coated fabric) out of which 2 Polyester and 2 Steel Plies.
Special Terrain Type Markings
There are few additional markings on the tires which are used to denote the special terrains in which that tire can be used, few of these markings are explain as follows:
- M+S – This marking means Mud + Snow terrain, it represents that tire is suitable for limited Mud and Snow usage. Few other notations which represents same are “MS,” “M/S,” or “M&S.”
- Mountain – Snowflake Symbol – This mark is commonly found on winter/snow tires. Tires that meet the RMA definition for tires for use in severe snow conditions are marked on at least one sidewall with the letters “M” and “S” (as stated above) plus the mountain snowflake symbol.
Tread-wear, Traction & Temperature Grades Marking
- Treadwear is determined by comparing the subject tire against a control tire that is assigned a grade of 100. If the subject tire gets a grade of 200, it can be expected to last twice as long as the control tire; a tire with a grade of 80 usually is less durable.
- Temperature, the tire’s heat resistance, is stated in letters. A tire graded “A” is the highest, “B” is average and “C” the lowest. The “C” grade represents the minimum performance standard required by federal regulation.
Traction also receives letter grades that indicate how well it stops. A tire having a higher grade should allow a car to stop on a wet road in a shorter distance than a tire with a lower grade. Traction is graded “AA” (highest), “A,” “B” or “C” (lowest).
In case you have any query regarding truck & trailer tires, feel free to drop a comment. Our team of tire experts will be more than happy to solve your queries and help you in choosing the best suitable tires for your truck or trailer.