Where Is The Serial Number On A Tyre

[Zoraida]

Loweraspect ratio tires, such as a 60 series, generally offer vehicle handling performance advantages over higher aspect ratio tires, such as a 75 series, but a typical trade off can be ride harshness.

There are two types of load types for passenger tires though, Standard Load and Extra Load. If a tire is Standard Load there will be no markings indicating it but if it is Extra Load the letters XL will appear after the size and load index.

Passenger car tires like P-Metric and Euro-Metric will only have one load index number where LT-Metric and Euro-Metric Commercial (C-Type) will have two numbers separated by a slash. The first number is the load index if the tire is used in a single application, the second number is the load index if the tire is used in a dual application. Passenger type tires cannot be used in a dual application. Light truck tires will also have a Load Range that is indicated by a letter, such as Load Range E. Load Range is an older term that is still commonly used in the industry so you may hear your tire dealer reference it but the load index numbers are the best way to ensure you have the proper tire.

The final figure in a tire size sequence is the speed rating, which is indicated by a letter: P225/70R16 91S. Just as your load index number corresponds to a specific load, your speed rating letter corresponds to a particular speed capability based on a standardized laboratory test.

Load Index and Speed Rating have the same meaning and format as the tires using the metric sizing system. Note that since flotation tires cannot be used in a dual application there will be only one load index number instead of two.

Another group of stamping on certain types of tires is the Uniform Tire Quality Grading or UTQG. This grading and stamping is required for passenger car tires (i.e. P-metric and Euro-metric) in the all season and summer categories. Dedicated winter tires, Light Truck (LT-Metric, Euro-Metric Commercial, Flotation) and Motorcycle tires are excluded from this requirement.

Quality grading designates the comparative performance levels of a tire based on government-specified tests but commissioned by the individual tire manufacturers. All tire manufacturers are required to grade regular and all-season passenger tires in three categories:

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 6,000 miles (9,600 km). For example, a tire graded 150 would wear one and a half times as well on the government course as a tire graded 100. However actual tire performance depends on driving habits, road characteristics, service practices, and other factors that can influence the outcome.

Traction Grades AA, A, B and C

The traction grades from highest to lowest are AA (the highest), A, B and C. They represent how well tires stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. C-rated tires will have the lowest traction performance.

WARNING: THE TEMPERATURE GRADE 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.

In this article, you will learn to read a tyre size and its maximum load and speed and find out how the brand, range and tyre type, are shown on your tyre. You will also learn about other tyre markings such as the snowy mountain symbol, M+S letters and the significance of the OE marking.

The first of the two numbers is the nominal section width of the tyre. It is given in millimetres and defines the distance between the inner and outer sidewall of the tyre. For example, 205 means that your tyre is nominally 205 mm wide.

Radial technology, invented by Michelin, uses combinations of rubbers and metal and textile reinforcing materials to form very robust structures in the tread area but flexible sidewalls. It allows a longer tread life and reduces fuel consumption thanks to the reduction of the rolling resistance.

On the sidewall of your tyre you will find a number followed by a letter.

The tyre load rating or load index (in our example: 91) is a code which corresponds to a maximum load (in kg) that can be carried by a single tyre.

The tyre speed rating (in our example: V) is a code which corresponds to the maximum speed at which a tyre can carry its maximum load.

You will find a table of correspondence between these codes and their values in our article on load and speed ratings. These ratings are important information, as is tyre size, especially when considering choosing new tyres for your car.

The word "Tubeless" on the sidewall of your tyre indicates that your tyre does not require an inner tube. Note that a tube is sometimes necessary for certain wheels, but in such cases it is important to assess if the tube and tyre are compatible.

Conversely, the word "Tube type" indicates that the tyre requires to be fitted with a tube.

What is the benefit? A tubeless assemby is lighter, more fuel efficient and often more reliable owing to damage that can occur to the tube in service.

There are markings on the sidewall of the tyre (MAXLOAD and MAX PRESS) that indicate the maximum load and the maximum pressure of the tyre. However, these are not necessarily the load and pressure values for your vehicle.

To ensure that your tyres perform correctly on your vehicle, you must refer to the inflation pressures recommended by the manufacturer of your vehicle. These can normally be found in your owner's manual or on the sticker in the driver's door or fuel filler cap.

Know more about how to check tyre pressure.

The tyre date code appears in the DOT (Department Of Transportation) field, where other tyre markings are present.

The first codes are for the US market requirements. The date code appears at the end, with four numbers.

The first two numbers designate the week and the last two numbers, the year of production. In this example, the tyre date code indicates 4714, which means that the tyre was manufactured in the 47th week of the year 2014.

On MICHELIN tyres, you can easily identify them by the little Michelin Man symbol that appears in several places on the sidewall of the tyre. When you see the Michelin Man, you know that the wear indicators are arranged in line across the width of the tyre.

1 - Snowy mountain

A logo consisting of a mountain of 3 peaks with a snowflake may be present on your tyre. This is the three peak mountain snowflake or 3PMSF label: the most recent standard for winter or snow tyres. It guarantees a minimum level of winter performance because there is an objective test for tyres marked in this way. This logo on your tyre ensures that it is considered as recommended equipment to access areas under regulation such as ski resorts, for example.

For winter certified tyres (M+S and/or 3PMSF marking), the speed capacity may be lower than that of the original summer tyres. Therefore, if necessary, the vehicle speed must be limted accordingly with winter tyres fitted. In some countries, for example where the theoretical speed limit for the car may be above the speed limit of the tyres, a sticker showing this lower speed may be required inside the vehicle, clearly visible to the driver.

Some car manufacturers equip vehicles with tyres tuned specifically for their requirements.

A marking on the tyre, meaning "Original Equipment", indicates that the tyre was designed by the tyre manufacturer and approved by your vehicle manufacturer to be fitted as standard.

The OE marking refers not only to the Manufacturer but often the specific car model. The differences between tyres of these types might relate to vehicle handling, comfort, noise and sometimes the requirements of the transmission and vehicle software systems. Also, the rolling resistance is optimised.

For a truly unique driving experience, Michelin's extensive engineering expertise allows it to select the ideal materials and technologies in order to design bespoke tyres for a variety of car models.

Installing the right tires on your vehicle is essential to the overall performance and safety of your vehicle. Your tire choice should reflect the conditions in which you drive and your preferences for vehicle response and handling. To make the most informed decision, though, you must understand how to read tire size when it's time to buy tires.

Thankfully, determining the correct tire size for your vehicle is relatively simple. All the information you need is immediately available either in your owner's manual or somewhere on the vehicle itself. Already know how to read tire size numbers? Skip the explanation and find the right Bridgestone tire for your vehicle online or by visiting a Bridgestone tire dealer near you.

While actual, physical measurements like width and diameter are factors in finding the right tire size, there are additional details to consider. Knowing how to read car tire sizes also means understanding terms like load index and speed rating that affect your vehicle's overall capabilities.

For most vehicles, you'll see the letter "P" before the number sequence begins: P225/70R16 91S. The "P" is short for "P-metric," which is a designation by the Tire and Rim Association for a "passenger car" tire type. A "P" signifies the tire was designed to primarily be used on passenger vehicles, which can include cars, minivans, SUV's and other light-duty pickup trucks.

Similarly, "T" stands for "temporary" and is for your spare tire. If you see "ST," that means "special trailer." A special trailer tire is never installed on the drive or steer wheels. It's only intended for use on trailer axles.

After the slash mark, the next number you see is for the tire's aspect ratio, which essentially tells you how tall your tire's profile is: P225/70R16 91S. Aspect ratios are delivered in percentages. Tire makers calculate the aspect ratio by dividing a tire's sidewall height by its width. If a tire has an aspect ratio of 70, it means the tire's height is 70% of its width.

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