词条 | Tire code | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
释义 |
Automobile tires are described by an alphanumeric tire code (in American English and Canadian English) or tyre code (in British English, Australian English and others), which is generally molded (or moulded) into the sidewall of the tire. This code specifies the dimensions of the tire, and some of its key limitations, such as load-bearing ability, and maximum speed. Sometimes the inner sidewall contains information not included on the outer sidewall, and vice versa. The code has grown in complexity over the years, as is evident from the mix of SI and imperial units, and ad-hoc extensions to lettering and numbering schemes. New automotive tires frequently have ratings for traction, treadwear, and temperature resistance (collectively known as The Uniform Tire Quality Grade (UTQG) ratings). Most tires sizes are given using the ISO Metric sizing system. However, some pickup trucks and SUVs use the Light Truck Numeric or Light Truck High Flotation system. National technical standards regulationsThe European Tyre and Rim Technical Organisation (ETRTO) and the Tire and Rim Association (TRA) are two organizations that influence national tire standards. The objective of the ETRTO include aligning national tire and rim standards in Europe.[1] 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.[2] 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).[3] Canada has published tire regulations, such as the Motor Vehicle Tire Safety Regulations SOR 95-148.[4] Explanation of tire codesThe ISO Metric tire code consists of a string of letters and numbers, as follows:
P indicates that the tire is engineered to TRA standards, and absence of a letter indicates that the tire is engineered to ETRTO standards. 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.[5]
Flotation sizesSome light-truck tires follow the Light Truck Numeric or Light Truck High Flotation systems, indicated by the letters LT at the end instead of the beginning of the sequence, as follows:
As an example, if a tire size has two sets of numbers (6-12, 5.00-15, 11.2-24), then the first number (5.00-15) is the approximate width in inches, and the second number (5.00-15) is the rim diameter in inches. If a tire size has three sets of numbers (15x6.00-6, 26x12.00-12, 31x15.50-15), then the first number (26x12.00-12) is the approximate height in inches, the second number (26x12.00-12) is the approximate width in inches, and the third number (26x12.00-12) is the rim diameter in inches.[9] Load rangeThe Load Range Letter on light-truck tires indicates their ply rating.[10]
{{anchor|Load index}} Load indexThe load index on a passenger-car tire is a numerical code stipulating the maximum load (mass, or weight) each tire can carry. For Load Range "B" tires, ETRTO (ISO-Metric) standards specify the load index rating at an inflation pressure of {{convert|36|psi|kPa|abbr=on}} (table below), while P-Metric standards measure the load capacity at an inflation pressure of {{convert|35|psi|kPa|abbr=on}}. The two standards vary slightly with the capacity required for different inflation pressures.[11] While all ETRTO tires of the same load index will have the same maximum load, P-Metric tires with the same load index may have different load capacities depending on the tire size. The TRA Inflation Tables must always be consulted when comparing the load capacity of P-Metric tires; the Load Index alone is not sufficient. An example: a P205/50R15 Standard Load tire has a load index of 84 and a load rating of {{convert|1113|lb|kg|order=flip|abbr=on}} at {{convert|35|psi|kPa|abbr=on}}. A P215/50R13 with the same load index of 84 only has a load rating of {{convert|1091|lb|kg|order=flip|abbr=on}}, also at {{convert|35|psi|kPa|abbr=on}}.[12] ETRTO produces a Standards Manual (current edition 2010), which contains a number of specifications and tables. The load index table (2010 page G7) lists the Load index from {{convert|0|-|45|kg|lb|abbr=on}} to {{convert|279|-|136000|kg|lb|abbr=on}} (although it appears to relate to an inflation pressure of {{convert|42|psi|kPa|abbr=on}} it doesn't specify, but see Load Inflation Table).[13] The Load Inflation Table references the load index to inflation pressures between {{convert|22|psi|kPa|abbr=on}} and {{convert|42|psi|kPa|abbr=on}} at {{convert|1|psi|kPa|abbr=on}} intervals which is too large to be included here.[12]
Some of the older letter-code load-range ratings for Light Truck Tires can be found in a chart[14] published by the Goodyear Tire & Rubber Company. For example:
{{anchor|Speed rating}} Speed ratingThe speed symbol is made up of a single letter or an A with one numeral. It indicates the maximum speed at which the tire can carry a load corresponding to its Load Index.[13] The testing method consists of pressing the tire against a large diameter metal drum to reflect its appropriate load, and run at ever increasing speeds in 10 km/h (6.2 mph) steps in 10 minute increments until the tire's required speed has been met.[15]
Prior to 1991, tire speed ratings were shown inside the tire size, before the "R" construction type. The available codes were SR (180 km/h, 112 mph), HR (210 km/h, 130 mph), VR (in excess of 210 km/h, 130 mph). Tires with a speed rating higher than 300 km/h (186 mph) are indicated by a Y in parentheses. The load rating is often included within the parentheses, e.g. (86Y). In many countries, the law requires that tires must be specified, and fitted, to exceed the maximum speed of the vehicle they are mounted on, with regards to their speed rating code (except for "temporary-use" spare tires). In some parts of the European Union, tires that are not fit for a car's or motorcycle's particular maximum speed are illegal to mount. The sole exception are M+S tires, where a warning sticker stating the allowed maximum speed must be placed within clear sight of the driver inside the vehicle. Some manufacturers will install a speed governor if a vehicle is ordered with tires rated below the vehicle's maximum speed. In some parts of the European Union, e.g. Germany, it is allowed to mount tires with a lower speed rating code if the car manufacturer specifies tires with a very high speed rating in the registration documents and the vehicle will not reach this speed based on insufficient power.[16] In this case it is possible to calculate the appropriate speed rating with a formula.[17] Metric to Imperial tire conversion chartR15215/75/15 27.7"x 8.5" 225/70/15 27.4"x 8.9" 225/75/15 28.3"x 8.9" 235/75/15 29.0"x 9.3" 245/75/15 29.5"x 9.6" 255/75/15 30.0"x 10.0" 265/75/15 30.6"x 10.4" R16205/85/16 29.7"x 8.1" 215/75/16 28.7"x 8.5" 225/70/16 28.4"x 8.9" 225/75/16 29.2"x 8.9" 235/70/16 29.0"x 9.3" 235/85/16 31.7"x 9.3" 245/70/16 29.5"x 9.6" 245/75/16 30.5"x 9.6" Wheel/Rim widthsTo determine the allowable range of rim widths for a specific tire size, the TRA Yearbook or the manufacturer's guide should always be consulted for that specific tire—there is no rule of thumb.[18] Running a tire on a rim size or type not approved by its manufacturer can result in tire failure and a loss of vehicle control. Additional marksThere are numerous other markings on a typical tire, these may include:
Tire geometryWhen referring to the purely geometrical data, a shortened form of the full notation is used. To take a common example, 195/55R16 would mean that the nominal width of the tire is approximately 195 mm at the widest point, the height of the side-wall of the tire is 55% of the width (107 mm in this example) and that the tire fits {{convert|16|in|mm|adj=mid|-diameter}} wheels. The code gives a direct calculation of the theoretical diameter of the tire. For a size shown as "T/A_W" use (2×T×A/100) + (W×25.4) for a result in millimeters or (T*A/1270)+ W for a result in inches. Take the common example used above; (2×195×55/100)+(16×25.4) = 621 mm or (195×55/1270)+16 = 24.44 inches. Less commonly used in the US and Europe (but often in Japan for example) is a notation that indicates the full tire diameter instead of the aspect ratio of the side-wall height. To take the same example, a 16-inch wheel would have a diameter of 406 mm. Adding twice the tire height (2×107 mm) makes a total 620 mm tire diameter. Hence, a 195/55R16 tire might alternatively be labelled 195/620R16. Whilst this is theoretically ambiguous, in practice these two notations may easily be distinguished because the height of the side-wall of an automotive tire is typically much less than the width. Hence when the height is expressed as a percentage of the width, it is almost always less than 100% (and certainly less than 200%). Conversely, vehicle tire diameters are always larger than 200 mm. Therefore, if the second number is more than 200, then it is almost certain the Japanese notation is being used—if it is less than 200 then the U.S./European notation is being used. The diameters referred to above are the theoretical diameter of the tire. The actual diameter of a specific tire size can only be found in the TRA Yearbook or the manufacturer's data books.[23] Note that the tire's cross-section and diameter are always specified when measured on a wheel of a specified width; different widths will yield different tire dimensions. ExamplesThe tires on a BMW Mini Cooper might be labeled: P195/55R16 85H
The tires on a Hummer H1 might be labeled: 37X12.5R17LT
Historical tire codesNorth AmericaPrior to 1964, tires were all made to a 90% aspect ratio. Tire size was specified as the tire width in inches and the diameter in inches - for example 6.50-15.[24] From 1965 to the early 70's, tires were made to an 80% aspect ratio. Tire size was again specified by width in inches and diameter in inches. To differentiate from the earlier 90-ratio tires, the decimal point is usually omitted from the width - for example 685-15 for a tire 6.85 inches wide. Starting in 1972 tires were specified by load rating, using a letter code. In practice a higher load rating tire was also a wider tire. In this system a tire had a letter, optionally followed by "R" for radial tires, followed by the aspect ratio, a dash and the diameter - C78-15 or CR78-15 for bias and radial respectively. Each diameter of wheel had a separate sequence of load ratings, thus a C78-14 and a C78-15 are not the same width. 78% aspect ratio was typical for letter sized tires, although 70% was also common and lower profiles down to 50% were occasionally seen.[25] See also
References1. ^About us, European Tyre and Rim Technical Organisation. Retrieved 2010-01-05. {{refbegin}}2. ^Scope of the Association and Some of its History {{webarchive|url=https://web.archive.org/web/20100303220431/http://www.us-tra.org/traAbout.html |date=2010-03-03 }}, The Tire and Rim Association. Retrieved 2010-01-04. 3. ^Laboratory Test Procedure for FMVSS 120 {{webarchive|url=https://web.archive.org/web/20090702224742/http://www.nhtsa.dot.gov/staticfiles/DOT/NHTSA/Vehicle%20Safety/Test%20Procedures/Associated%20Files/TP120-03.pdf |date=2009-07-02 }}, National Highway Traffic and Safety Administration, United States Department of Transportation, April 10, 2000. Retrieved 2010-01-05. 4. ^Motor Vehicle Tire Safety Regulations SOR 95-148, Canadian Legal Information Institute. Retrieved 2010-01-05. 5. ^Care and Maintenance - Technical {{webarchive|url=https://web.archive.org/web/20100115092140/http://dunloptires.com/care/tech.html |date=2010-01-15 }}, Dunlop Tires. Retrieved 2010-01-05. 6. ^A brief history of radial tires and the offbeat TRX system, Michelin TRX, Dr. Theo Netherlands. Retrieved 2010-01-05. 7. ^Similarly, whilst most bicycle wheels have a diameter measured in inches, the 700mm wheel (=27.56") is increasingly common. 8. ^{{cite web |url=http://www.toyotraining.com/toyo_fund_8.php |title=Archived copy |accessdate=2014-09-30 |deadurl=yes |archiveurl=https://web.archive.org/web/20141006070043/http://www.toyotraining.com/toyo_fund_8.php |archivedate=2014-10-06 |df= }} 9. ^{{cite web| url=http://www.millertire.com/faqs/| title=FAQ's| accessdate=2013-06-27}} 10. ^"2010 Year Book",The Tire and Rim Association, Inc.,Preface p XVII 11. ^Guidelines for the Application on Load and Inflation Tables {{webarchive|url=https://web.archive.org/web/20100331144143/http://marktg.toyotires.com/file/loadinflationtable.pdf |date=2010-03-31 }}, Toyo Tires. Retrieved 2010-01-05. 12. ^1 Guidelines for the Application on Load and Inflation Tables {{webarchive|url=https://web.archive.org/web/20100331144143/http://marktg.toyotires.com/file/loadinflationtable.pdf |date=2010-03-31 }}, Toyo Tires. Retrieved 2010-01-05. 13. ^1 2 3 European Tyre and Rim Technical Organisation Standards Manual 2010 G6{{dead link|date=March 2018 |bot=InternetArchiveBot |fix-attempted=yes }}, 14. ^"Goodyear Truck Tires Service Manual", Section 11, Retreading, p107 {{webarchive|url=https://web.archive.org/web/20130520135728/http://www.goodyeartrucktires.com/pdf/resources/service-manual/Retread_S11_V.pdf |date=2013-05-20 }} 15. ^https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=35#speedrating 16. ^{{cite web |url=http://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CELEX:31992L0023&rid=4 |title=Council Directive 92/23/EEC of 31 March 1992 relating to tyres for motor vehicles and their trailers and to their fitting |author= |date= |work= |publisher=THE COUNCIL OF THE EUROPEAN COMMUNITIES |accessdate=2014-12-06 }} 17. ^{{cite web |url=http://www.auto-motor-oel.de/ratgeber/geschwindigkeitsindex-reifen/442/#Geschwindigkeitsindex-berechnen |title=How to calculate speed ratings |author= |date= |work= |publisher=Auto Motor Öl |accessdate=2014-12-06 }} 18. ^"Bridgestone Product Reference Guide",The Bridgestone Tire & Rubber Co. 19. ^1 2 3 4 5 6 7 "Bridgestone Product Reference Guide",The Bridgestone Tire & Rubber Co.,Core Tire Knowledge: Glossary 20. ^{{cite web|url=http://us.coopertire.com/Tire-Safety/FAQ.aspx|title=FAQ|author=|date=|work=|publisher=Cooper Tire|accessdate=|deadurl=yes|archiveurl=https://web.archive.org/web/20130801040907/http://us.coopertire.com/Tire-Safety/FAQ.aspx|archivedate=2013-08-01|df=}} 21. ^"Bridgestone Product Reference Guide",The Bridgestone Tire & Rubber Co.,Technical Bulletins: Tire Inspection Guidelines 22. ^{{cite web |url=http://www.yokohamatire.com/customer_service/tirecare_matchmounting.aspx |title=Tire care -- Match mounting |author= |date= |work= |publisher=Yokohama Tire Corporation |accessdate= }} 23. ^"2010 Year Book",The Tire and Rim Association, Inc. 24. ^{{cite web |url=http://www.vintagecarconnection.com/vintage_tire_size_conversion_chart.htm |title=Vintage Tire Size Conversion Chart |author= |date= |work= |publisher= |accessdate= }} 25. ^{{cite web |url=http://www.tirerack.com/tires/tiretech/45_conversionchart.html |title=Tire Size Conversion Chart |author= |date= |work= |publisher= |accessdate= }} External links
2 : Tires|Encodings |
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