Tires and Markings Explained Tires and Markings Explained


description of passenger tires
Letter Rating Speed Rating
Q 99 mph
R 106 mph
S 112 mph
T 118 mph
U 124 mph
H 130 mph
V 149 mph
W *168 mph
Y *186 mph
*For tires with a maximum speed capability over 149 mph, tire manufacturers sometimes use the letters ZR. For those with a maximum speed capability over 186 mph, tire manufacturers always use the letters ZR. See Chart Below.
All tires sold in the United States must meet the size standards for bead shape, width, diameter and other parameters established by a recognized standardizing organization. World leaders among such organizations are the European Tire and Rim Technical Organization (ETRTO) and the U. S. Tire and Rim Association (T&RA). Both use a partially metric based system. Virtually all passenger tires on the market today use the rim and tire sizing, load and inflation system established by these bodies. All U. S. highway tires must also meet U. S. DOT standards as indicated by the letters 'D.O.T.' on the sidewall. The several tire size designations in use today depend on when a vehicle was manufactured and whether it was domestic or imported. All tire-sizing systems used today provide information about a tire's dimensions. Among the most important for proper fitment is height, width and load carrying capacity.

This is the United States version of a metric sizing system established in 1976. P-Metric passenger car tire sizes begin with "P", which simply means "Passenger".

This European tire sizing system is similar to P-Metric but does not use the "P" designator.

This system was established in 1968 and is based on the tire's load carrying capacity, correlated to its overall size. The tire's capacity and size are indicated by letter designations from "A" (smallest tire, lowest capacity) to "N" (largest tire, highest capacity). An example of an Alphanumeric tire size is BR78-13. "B" shows size/load, "R" indicates radial construction, "78" is the aspect ratio, and "13" is the wheel size in inches.

This is the oldest standardized tire sizing system for passenger car tires. When this system was adopted, tire aspect ratios were either 92 or 82. For example, a 7.00-14 tire has a section width of 7 inches, a rim diameter of 14 inches and an aspect ratio of 92. The low profile equivalent size tire with an aspect ratio of 82 would be 7.35-14.**** Example: P215/65R15 89H

This indicates a passenger car tire. If the first character in the size designation is a "P", the tire is a "P-Metric" tire and is engineered to standards set by the T&RA (Tire and Rim Association). If there is no "P", the tire is engineered to ETRTO (European Tire and Rim Technical Organization) standards and is a metric tire. The standards set by T&RA and ETRTO have evolved together and are virtually interchangeable.

These numerals indicate the tire section width in millimeters. This is the dimension from sidewall to sidewall. A tire's section width will vary depending on the rim to which it is fitted. The section width will be larger on a wide rim and smaller on a narrow rim. Therefore, each tire is measured to specific rim width. (To convert millimeters into inches, divide by 25.4.)

This two-digit number indicates the tire's aspect ratio. It compares the tire's inflated section height, which is the distance from the bead to the tread, to its section width (maximum). An aspect ratio of 65 means that the tire's section height is 65% of the tire's section width. For clarity, the section width in millimeters is separated from the aspect ratio by a slash (/).

This letter indicates the type of ply construction in the tire's casing or carcass. "R" means radial. "D" means diagonal, referring to bias ply tires. "B" means belted for belted-bias ply tires. Never mix radial tires with any other construction on a car.

The "15" indicates the rim diameter in inches. It is the diameter of the tire bead seat ledge in the rim. Most tires are built to inch standards for rim diameters. However, some tires are built to millimetric rim dimensions. Always match the tire's rim diameter to the wheel rim diameter. This is important for safety.

A millimetric rim has a different shape than an inch rim; they are not interchangeable.

The service description is an alphanumeric combination, consisting of two parts, a number and a letter. In this example 89 is the load index, which represents the load carrying capacity. (All passenger car tires in the US are also marked with their actual load limit in pounds). The letter part is the speed symbol, 'H,' in this example. This is the maximum speed for which the tire is rated at the load specified by the load index. In this example, 'H' means speeds up to 130 mph. Dunlop does not recommend the use of any of its products in excess of legal speed limits. Speed ratings do not necessarily imply that the performance (handling and grip) of the tire meet the performance standards implied by the ratings.. Dunlop designs tires to provide high performance levels commensurate with the higher speed ratings.

Tire speed ratings must exceed the maximum speed capability of the vehicle to which they are fitted. Not all tires sold in the US are speed rated, although many modern performance and luxury cars are equipped with speed rated OE tires. It is important to remember this when replacing the tires on your vehicle. Do not downgrade speed ratings from O.E. ratings.

Speed Ratings where applied are indicative of high performance characteristics based on European ECE 30 Indoor Wheel testing as performed by Dunlop and are not valid for damaged, altered, repaired, under-inflated, overloaded, excessively worn, or re-treaded tires. Dunlop does not recommend the use of any of its products in excess of legal speed limits.

Some tires carry additional markings related to service. An M&S or M+S designation means the tire is rated suitable by the manufacturer for mud and snow use. The guidelines are set by the Rubber Manufacturers Association (RMA) in the United States.

Is a marking which means that the tire meets M&S/M+S requirements without the drawbacks of noise and rolling resistance associated with the traditional deep-lug winter tires. The M&S/M+S designation means that the tire is suitable for normal all-weather driving applications. Tires that meet the requirements of the M& S designation have better winter traction compared to those without the M&S symbol.

In some heavy snow areas, local governments may require true snow tires, those with very deeply cut tread. These tires should only be used in pairs or placed on all four wheels. Make sure you purchase snow tires that are the same size and construction type as the other tires on your vehicle.

RMA severe snow conditions - rated DOT

RMA Severe Snow Conditions-Rated
North American tire manufacturers and the Rubber Manufacturers Association (RMA) have established a voluntary, industry-wide definition for passenger and light truck tires intended for use in SEVERE SNOW CONDITIONS. Tires must meet a performance based criteria feature tread pattern, construction elements and materials which generally provide snow performance superior to that of tires bearing the RMA's current M&S Rating. Such tires will display a mountain/snowflake symbol.

The 10 digit DOT (Department of Transportation) code number molded into the sidewall designates the manufacturer and plant where the tire was produced, the tire line and size, and the week and year the tire was manufactured.

All passenger tires are marked on the sidewalls to indicate maximum load capacity and maximum inflation pressure. Truck tires will indicate recommended pressure for maximum loads for both dual and single application.

Red dots on Dunlop high performance tires for match mounting purposes. This dot marks the 'high spot' of the tire, which is then matched with the 'low spot' on the rim to cancel out harmonic vibration.

Download Tire Info Example

truck tires information
Tires for light trucks have other markings besides those found on the sidewalls of passenger tires.

The "LT" indicates the tire is for light trucks.Max. Load Dual kg (lbs) at kPa (psi) Cold
This information indicates the maximum load and tire pressure when the tire is used as a dual, that is, when four tires are put on each rear axle (a total of six or more tires on the vehicle).

Max. Load Single kg (lbs) at kPa (psi) Cold
This information indicates the maximum load and tire pressure when the tire is used as a single.

This information identifies the tire's load-carrying capabilities and its inflation limits.

Tire Speed-Rating System
Tire Tips Chart
Rotating tires from front to back and from side to side can reduce irregular wear (for vehicles that have tires that are all the same size).
Look in your owner's manual for information on how frequently the tires on your vehicle should be rotated and the best pattern for rotation.
*For maximum mileage, rotate your tires every 5,000 miles. Follow correct rotation patterns.

Tire Rotating
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