Reading A Tire

1 Tire Size Specifications

The tire size helps you determine what size you must buy for the new tires. Going for new tires with the same tire specification is generally the best idea as it eliminates any guesswork that goes into upgrading tires. Simply remove the old ones and swap them out for new ones. The trick here is to focus on three primary numbers, for example, a tire with P205/55R16 90H – the three primary numbers will be 205, 55, and 16. 205 tells you how wide the tire tread is in millimeters. 55 refers to the aspect ratio of tire sidewall which is a representation of the sidewall height as a factor of the width of the tire. So the actual sidewall height here will be 113 mm (~4.5 inches). Refer to this guide to learn more about how to calculate tire size in mm and inches. Finally, 16 indicates the wheel or rim diameter in inches. 

The ‘P’ in the specs refers to passenger tires according to the p-metric standards. Some tires have no letter preceding the number, which also means passenger tire. While an ‘LT’ prefix refers to light trucks for truck and SUV tires. The ‘R’ after the aspect ratio refers to the tire construction. There are basically 3 types of tire constructions, R stands for radial construction (found in modern tires). B means belted bias and D stands for diagonal bias construction. 

When searching for new tires, all you have to do is to opt for the same specifications as the three primary numbers and you will have the right tire size for your wheels. This is the most simplified form of choosing new tires. There are however other factors to be considered like the speed rating and load index.

2 Tire Load Index And Speed Rating

The numbers and letters that follow the size specifications are the load index and speed rating in order. Essentially, what they mean is how much load each tire is tested to withstand and the maximum speed it was designed to handle. These numbers and letters are derived from a standardized set of values that are showcased in the table

The basic rule here is to stick to the manufacturer’s recommended tire load index and speed rating. These values are usually depicted on the tire placard found on the driver or passenger door jam. Since these are carefully calculated and derived by the manufacturer while designing the vehicle, changing it is not recommended. The speed rating is considered based on the car’s top speed. H means the tire is rated to go 210 km/h (130 mph) which is common to many sedans. Opting for a larger speed rating such as V or W will only cost more and will not be useful unless you have made considerable horsepower upgrades to your vehicle. T and H are common for cars that are often driven on highways. You can stick to S if you do not do many highway runs. 

3 DOT Codes

The US Department of Transportation or DOT and Transport Canada assigns a set of codes for each tire, which mainly concerns the tire manufacturer except for the manufacturing year. It starts with 2-3-symbols that represent the plant code where the tire was manufactured. Every manufacturer’s plant in every country has a different plant code. The two following symbols show tire size, but only according to the manufacturer and so it does not concern the customers. The next 3-4-symbol code is moulded solely for the manufacturer and is used by them for identification. The last 4 digits are crucial for the customer as it displays the tire manufacturing date. The first pair stand for the week of manufacture and the last pair shows the year. So, for example, the ‘1903’ code translates to 19th week of the year 2003 and ‘03’ is for the year. 

An interesting fact: For years before 2000, this code was only 3 digits long, as it only showed the decade instead of the actual year. 

The date code is very useful as it can help you know how old your tires are and also help you when purchasing new ones. Generally, tires last about 10 years, whether used or stored, and manufacturers recommend swapping them out if they are 6 years or older. When buying new tires make sure they are not more than a couple of years old. 

4 UTQG Codes

UTQG or Uniform Tire Quality Grade standards are codes that provide estimates of various tire characteristics based on the manufacturer’s tests and can be used to distinguish between different tires that you may be considering buying, to an extent.

Treadwear

This is a 3 digit number starting with 100. A larger number will be more wear-resistant and hence will last longer. Since these tests are conducted differently by each manufacturer, the rating only provides a ballpark estimate for comparison’s sake. 

Traction

This showcases the gripping power of the tire stated as AA, A, B, and C. where AA is the best and C the worst. This score indicates a tire’s wet-stopping ability. 

Temperature

This is also stated in terms of letters – A (best), B and C. This value evaluates the tire’s safe heat dissipativity. A tire that can dissipate heat more effectively will undergo lesser wear and subsequently lasts longer. 

5 Tire Pressure

The maximum cold tire pressure is mentioned on the sidewall of the tire closest to the wheel, alongside the maximum load capacity. However, this is not the same as the recommended pressure that you have to run the tires with. This number merely shows how much the tire can be safely inflated and does not correlate to the pressure the tires should be used in. You must always stick to the vehicle manufacturer-recommended tire pressure found on the car door sill or in the owner’s manual. 

6 Tire Ply Composition And Materials

You can also find information on the tire’s internal construction, which is located next to the maximum tire pressure. This data includes the ply composition, the number of layers, and the materials used in the construction. This is mainly displayed for manufacturers and legal reasons and holds no importance to the consumer. 

7 Severe Service Emblem

Certain tires with winter traction capabilities are graded with an emblem that identifies winter grip and performance. There are two grading systems: ‘M=S’ and 3 peaked mountain/snowflake symbols (3PMSF). These symbols are designated to tires after they pass a certain industry standard winter traction test. The ‘M=S’ symbol is used on tires that perform moderately well in snow, however, the tires are not rated for ice, slush, and cold dry roads. The more modern 3PMSF pictograph certifies tires that match more stringent winter traction tests, allowing them to be used in snow, ice, slush, and even cold dry roads. Dedicated winter tires and some all-weather tires come with the 3PMSF symbol, and the ‘M+S’ symbol is found on some all-season tires. 

8 How to Tell the Ply of Tire?

The ply rating of a tire is an indicator of its strength and load-carrying capacity. It is typically indicated by the Load Range on the tire’s sidewall, which is an alphanumeric code that represents the tire size and specifications. The Load Range letter corresponds to a specific ply rating, which gives an indication of the tire’s strength and load-carrying capacity. For instance, a Load Range E typically corresponds to a 10-ply rating.

If you don’t have access to the Load Range, you can determine the ply rating of a tire by looking for the Construction Type or Load Range markings on the tire’s sidewall. The Construction Type or Load Range markings are typically located adjacent to the tire size and specifications. The Load Range and ply ratings are used interchangeably, and the Load Ranges range from A to F.

9 How to Read Tire Codes?

To read a tire, you can look for the following information on the sidewall of the tire:

1. Manufacturer and tire name: These are printed in large letters toward the outside of the tire. They say the name brand of the company, such as Hankook, or Michelin, or Goodyear.
2. Service description: This comes in either a “P,” “LT,” “ST,” or “T.” “P” stands for passenger car. “LT” stands for light truck. “ST” stands for special trailer. “T” stands for temporary, and is borne by spare tires. “BP” stands for cosmetically blemished passenger.
3. Width and aspect ratio: This is a series of numbers right after the service description. The first series of three numbers tells you the width of the tire tread in millimeters. The two numbers after the slash show the aspect ratio of the tire. This is the tread-width percentage that is equal to the sidewall’s height.
4. Internal construction of the tire: This mark usually comes right after the aspect ratio. “R” stands for radial construction, an industry standard for passenger cars. Some trucks may have a “B” instead, which stands for bias-ply, but which has largely been discontinued due to poor handling issues.
5. Rim diameter: This is the rim size for which the tire was fitted. The letters in the position of SC or C signify the speed rating of the tire (pre-1991) or the construction of the tire. An “R” means the tire is of radial construction. If there is an “HR,” this is a high-speed radial tire.
6. Load index: This number is extremely important, as the load index is the tire size’s relative load carrying capabilities. The higher the load index number, the larger load carrying capacity.

10 How to Tell What Type of Tire You have?

To determine the type of tire you have, you can look at the sidewall of the tire. The sidewall is the outer wall of the tire, rather than the tread that contacts the road. The tire size is printed on the sidewall, and it contains a series of letters and numbers that provide information about the tire’s size, construction, and performance characteristics. Here’s how to read the tire size:

1. Find the series of letters and numbers on the sidewall. The tire size is printed on the sidewall of the tire, just above the rim of the tire. The series of letters and numbers should be printed underneath the tire manufacturer name.
2. Identify the service type. The first letter of the series denotes the service type. “P” stands for “P-metric” and denotes a passenger vehicle. “LT” stands for light truck, “T” means temporary spare, and “C” stands for commercial.
3. Determine the tire width. The first three-digit number identifies the tire width, which is measured from sidewall to sidewall and corresponds to the tread that contacts the road. The measurement is given in millimeters, and all four tires must have the same width.
4. Find the aspect ratio. The two-digit number after the slash indicates the aspect ratio, which compares the tire’s section height with the tire’s section width. If you’re replacing only one tire, make sure it has the same aspect ratio as the others.
5. Identify the tire construction. The next letter corresponds to the tire casing. “R” means radial construction, “B” stands for belted bias, and “D” means diagonal bias construction. Choose a spare or new tire with the same casing and construction as the rest.
6. Determine the rim diameter. The two-digit number after the letter indicates the rim diameter, which is essential to know if you’re getting new rims or wheels.

11 FAQs

What do Tire Specs Mean?

Tire specs are a series of letters and numbers printed on the sidewall of a tire that provide information about the tire’s size, construction, and performance characteristics. Here’s what each of the letters and numbers mean:

1. Tire type: The first letter of the series denotes the service type. “P” stands for “P-metric” and denotes a passenger vehicle. “LT” stands for light truck, “T” means temporary spare, and “C” stands for commercial.
2. Tire width: The first three-digit number identifies the tire width, which is measured from sidewall to sidewall and corresponds to the tread that contacts the road. The measurement is given in millimeters, and all four tires must have the same width.
3. Aspect ratio: The two-digit number after the slash indicates the aspect ratio, which compares the tire’s section height with the tire’s section width. If you’re replacing only one tire, make sure it has the same aspect ratio as the others.
4. Construction type: This single letter tells you about the internal construction of the tire. These include radial and bias. R stands for radial tires, the industry standard for most tires today.
5. Rim diameter: The two-digit number after the letter indicates the rim diameter, which is essential to know if you’re getting new rims or wheels.
6. Load index: This number is extremely important, as the load index is the tire size’s relative load carrying capabilities. The higher the load index number, the larger load carrying capacity.
7. Speed rating: The speed rating indicates the maximum speed at which the tire can carry a load safely. The rating is a letter that corresponds to a specific speed range.

What m+s Means in Tires?

The M+S marking on a tire stands for “Mud and Snow”. It’s a type of all-season tire designed to perform better than standard all-season tires in light snow and muddy conditions. Tires with the M+S designation have tread patterns that are designed to help shovel through the mud and snow, bigger gaps between tread blocks, and more siping. The U.S. Department of Transportation (DOT) requires that for a tire to carry the M+S symbol, it must have at least 25% more “void” (that’s the space between those tread blocks) than a regular street tire.

What Does 205/55r16 Mean?

The tire size “205/55R16” contains the following information:

• 205: The width of the tire tread in millimeters.
• 55: The aspect ratio of the tire, which is the height of the sidewall as a percentage of the tire’s width.
• R: The construction of the tire, which is radial.
• 16: The diameter of the wheel rim in inches.

What Does D Mean on a Tire?

The letter “D” on a tire indicates that the tire is classified under load range D. Built for light trucks, D-rated tires have a maximum pressure of 65 PSI (450 kPa) and an 8-ply rating, which enables them to be inflated and maintain their round shape. D-rated tires only provide more capacity if they are inflated to the higher-rated design pressure.

What Does p205 Mean on a Tire?

The “P” in “P205” stands for “Passenger Vehicle”. It indicates that the tire is designed for use on passenger cars, rather than light trucks or other types of vehicles. The “205” refers to the width of the tire tread in millimeters.

What Does 55r Mean on a Tire?

The “55” in “205/55R16” refers to the aspect ratio of the tire. The aspect ratio is the height of the tire’s sidewall as a percentage of the tire’s width. In this case, the sidewall height is 55% of the tire’s width.

The “R” in “205/55R16” refers to the construction of the tire, which is radial. Radial tires are the most common type of tire on the road today.