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The number may be longer where a half-inch size is used, for example many heavy transport trucks now use 22.5-inch tires. Few tires are made to this size currently. There is the rare exception of metric-diameter tires, such as the use of the 390 size, which in this case would indicate a wheel of 390 mm in diameter.
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1- or 2-digit number: Diameter in inches of the wheel that the tires are designed to fit.B: bias belt (where the sidewalls are the same material as the tread, leading to a rigid ride).An optional letter indicating construction of the fabric carcass of the tire:.If the letter here is Z, indicating a maximum speed in excess of 240 km/h (149 mph), then a more specific letter W or Y may appear after the load index (see speed rating, below). Alternatively, the letter may appear at the end, following the load index. An optional letter indicating the speed rating of the tire.If the number is larger than 200, then this is the diameter of the entire tire in millimeters. If the information is omitted, it is assumed to be 82% (if written, it should be like xxx/82). 2- or 3-digit number: The "aspect ratio" of the sidewall height as a percentage of the nominal section width of the tire./: Slash character for character separation.The tire surface that touches the road usually has a narrower width (called "tread width"). 3-digit number: The "nominal section width" of the tire in millimeters the widest point from both outer edges (side wall to side wall).In practice, the standards of the two organizations have evolved together and are fairly interchangeable, but not fully, since the load index will be different for the same size tire.
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P indicates that the tire is engineered to TRA standards, and absence of a letter indicates that the tire is engineered to ETRTO standards. T: Temporary (restricted usage for "space-saver" spare wheels).An optional letter (or letters) indicating the intended use or vehicle class for the tire:.
#Etrto standards and databooks for tire size code
The ISO metric tire code consists of a string of letters and numbers, as follows: "yy" is "aspect ratio" (sidewall height to tread width). Tire diameter (inches) = (xxx*yy/1270)+zz, where tire size is commonly written "Pxxx/yyRzz" on the sidewall. The last number outside the circle or rectangle is the number of the type approval certificate issued for that particular tire size and type. The number in the circle or rectangle denotes the country code of the government that granted the type approval. A (lower case) "e" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of Directive 92/23/EEC. An (upper case) "E" indicates that the tire is certified to comply with the dimensional, performance and marking requirements of ECE regulation 30. The mark itself is either an upper case "E" or lower case "e" – followed by a number in a circle or rectangle, followed by a further number. E-mark Īll tires sold for road use in Europe after July 1997 must carry an E-mark. Canada has published tire regulations, such as the Motor Vehicle Tire Safety Regulations SOR 95-148. In the United States, the Office of Vehicle Safety Compliance, a component of the Department of Transportation, is one of the agencies tasked to enforce the Federal Motor Vehicle Safety Standard (FMVSS). The Tire and Rim Association, formerly known as The Tire and Rim Association of America, Inc., is an American trade organization which standardizes technical standards. The objective of the ETRTO include aligning national tire and rim standards in Europe. The European Tyre and Rim Technical Organisation (ETRTO) and the Tire and Rim Association (TRA) are two organizations that influence national tire standards. In addition, it is a requirement for all tyres on these vehicles to display a legible date code. The ban also applies to all tyres in single configuration on minibuses. Since 1st February 2021 UK vehicle Regulations do not permit the use of tyres over 10 years old on the front steered axle(s) of heavy goods vehicles, buses and coaches. The DOT code is also useful in identifying tires subject to product recall or at end of life due to age. Department of Transportation but is used worldwide. The DOT code is an alphanumeric character sequence molded into the sidewall of the tire and allows the identification of the tire and its age. Main article: Tire § Regulation DOT code