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The Details About Tire Specs

Author: Maisie | Published on Tue Jan 27 2015 | Views : 8787 Tire Reviews0

The tire size branded on the sidewall provides a significant amount of information about the tire’s intended purpose, dimensions, load capacity and high temperature / high speed durability.

Our primary example will be based on variations of the 215/65R/15 size, although other sizes will appear where appropriate.

Tire Type

The letter “P” at the beginning of the “Tire Size” tells us the tire is a P-Metric, referring to tires made to certain standards within the United States, intended for Passenger vehicles.

If a tire size has no letters at the beginning, this indicates a Euro metric tire. P-Metric and Euro-Metric tires may have different load capacities.

If a tire size begins with a "T," it signifies the tire is a "Temporary Spare" ("space saver" or "mini spare") that was designed to be used temporarily only until a flat tire can be repaired or replaced.

The letters “LT”, either at the beginning or at the end of the tire size indicate the tire was designed for light trucks. Vehicle manufactures equip some light trucks with “LT” type tires. These tires generally require higher inflation pressures than passenger tires.

If a tire size begins with "ST," it signifies the tire is a "Special Trailer Service" size that was designed to only be used on boat, car or utility trailers. ST-sized tires should never be used on cars, vans or light trucks.

Consult your owner’s manual or tire placard for the recommended tire size and inflation pressure for your vehicle.

 

 

Tire Width

Tire Width is the width of the tire measured in millimeters from sidewall to sidewall. The first three-digit number in the tire size refers to the tire width. For instance, in a size P215/65 R15 tire, the width is 215 millimeters.

 

 

Aspect Ratio

Aspect Ratio is the ratio of the height of the tire’s cross-section to its width. The two-digit number after the slash mark in a tire size is the aspect ratio. For example, in a size P215/65 R15 tire, the 65 means that the height is equal to 65% of the tire’s width. The bigger the aspect ratio, the bigger the tire’s sidewall will be.

 

 

Internal Construction

The letter “R” in a tire size stands for Radial, which means the layers run radially across the tire.

 

 

Wheel Diameter

Wheel Diameter is the size of the wheel measured from one end to the other. It tells us the size of the wheel that the tire is intended to fit. A size P215/65 R15 tire is made for a wheel with a “15” diameter.

 

 

Load Index

"95H" means Load Index. The Load Index indicates the maximum load that the tire can support when properly inflated. You’ll also find the maximum load on the tire sidewall, in both pound and kilograms.

 

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Note: You may not find this information on all tires because it is not required by law.

 

M+S=MUD AND SNOW:The "M+S" or "M/S" indicates that the tire has some mud and snow capability. Most radial tires have these markings; hence, they have some mud and snow capability.

Speed Rating 

Speed Rating tells you the maximum speed capability of a tire. Often speed ratings are matched to the top speed capability of the vehicle. For example, a tire with an H-speed rating has a maximum speed capability of 130 mph or 210 km/h. 

 

Speed Rating Chart

Speed Rating     Max MPH      Typical Usage

   M             81mph

   N             87mph        Spare Tires

   P             93mph        

   Q             99mph        Winter Tires

   R             106mph       Truck Tires

   S             112mph        Cars and Minivans

   T             118mph        Cars and Minivans

   U             124mph        Sport-Performance Cars

   V             149mph        High-Performance Cars 

   W            168mph        Ultra High-Performance Cars

   Y             186mph        Ultra High-Performance Cars

 

DOT Symbol: The letters "DOT" on the sidewall indicate that the tire complies with all applicable Federal Motor Vehicle Safety Standards in the United States.

Tire Identification Number: The series of letters and numbers following the letters "DOT." The TIN consists of up to 12 numbers and letters to identify the factory location and the week and year the tire was manufactured.

UTQG stands for Uniform Tire Quality Grading, a rating system developed by the U.S. Department of Transportation to provide consumers with information to help them purchase tires based on their relative treadwear, traction and temperature capabilities.

Traction grades indicate the wet traction of a tire under a controlled test. A tire with an "AA" rating offers outstanding traction in wet conditions.

Traction Grades

AA

A

B

C

Temperature grades indicate the ability of the tire to withstand and dissipate destructive heat. A tire with a higher temperature grade is able to operate at higher speeds.

Temperature Grades

Speeds in mph

A

Over 115

B

Between 100 and 115

C

Between 85 and 100

Treadwear grades are based on standardized government tests to help predict the expected treadwear of a tire. For example, a tire with a treadwear grade of 200 should last twice as long as a tire with a treadwear grade of 100.

OE CODE: The annotation indicating that a specific tire is an Original Equipment (OE) approved tire by a specific Original Equipment vehicle manufacturer.

For instance, BM=BMW, GM= General Motors, HY=Hyundai, I=Infiniti, L-Lexus, MB=Mercedes-Benz, T= Toyota, V=Volvo. 

Tread Feature: Many Original Equipment vehicle manufacturers require a tire approval marking for the OE-approved tire . The marking ensure the consumer can purchase the OE-approved tire in the replacement market to maintain the vehicle’s OE performance.There have ASY and DT.

Sidewall: The sidewall is the portion of the tire between the tread and the bead. This area contains the manufacturer’s markings, including tire description, serial number, quality grade etc. For example, BSW=Black Sidewall.

RIM Width Range(MIN/MAX): The tire manufacturer’s recommended range for the tire size. A proper rim width ensures that the tire and wheel assenbly performance is optimized. Just like 7.5”-9”.

Section Width on Measuring RIM Width: Distance measured between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations) mounted on the nominal rim width to provide a good balance of ride, handling and tread life. Just like 9.6”8”.

Overall Diameter: The tire’s diameter in inches measured without any applied load. For instance, overall diameter is 26.7.

REVS/MI: Revolutions per mile (RPM) is the number of times a tire turns when traveling one mile. This number varies based on speed, load, and inflation pressure. Just like 780 revs/mi.

Max Load Single (LB@PSI): The highest load that can be applied to tire when used in a single tire application at the maximum inflation pressure.

Tire RotationAlways refer to your owner’s manual for a rotation schedule and pattern specific to your vehicle. However, a good rule of thumb is to rotate your tires about every 6,000-8,000 miles in order to avoid irregular tire wear.


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