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Message: <blockquote data-quote="Shifty Powers" data-source="post: 1162475" data-attributes="member: 9020">When Z-speed rated tires were first introduced, they were thought to reflect the highest tire speed rating that would ever be required, in excess of 240 km/h or 149 mph. While Z-speed rated tires are capable of speeds in excess of 149 mph, how far above 149 mph was not identified. That ultimately caused the automotive industry to add W- and Y-speed ratings to identify the tires that meet the needs of new vehicles that have extremely high top-speed capabilities. <table style='width: 100%'><tr><td>W</td><td>168 mph</td><td>270 km/h</td><td>Exotic Sports Cars</td></tr><tr><td>Y</td><td>186 mph</td><td>300 km/h</td><td>Exotic Sports Cars</td></tr></table>While a Z-speed rating still often appears in the tire size designation of these tires, such as 225/50ZR16 91W, the Z in the size signifies a maximum speed capability in excess of 149 mph, 240 km/h; the W in the service description indicates the tire's 168 mph, 270 km/h maximum speed. <table style='width: 100%'><tr><td>225/50ZR16</td><td>in excess of 149 mph, 240 km/h</td></tr><tr><td>205/45ZR17 88W</td><td>168 mph, 270 km/h</td></tr><tr><td>285/35ZR19 99Y</td><td>186 mph, 300 km/h</td></tr></table>Most recently, when the Y-speed rating indicated in a service description is enclosed in parentheses, such as 285/35ZR19 (99Y), the top speed of the tire has been tested in excess of 186 mph, 300 km/h indicated by the service description as shown below: <table style='width: 100%'><tr><td>285/35ZR19 99Y</td><td>186 mph, 300 km/h</td></tr><tr><td>285/35ZR19 (99Y)</td><td>in excess of 186 mph, 300 km/h</td></tr></table>As vehicles have increased their top speeds into Autobahn-only ranges, the tire speed ratings have evolved to better identify the tires capability, allowing drivers to match the speed of their tires with the top speed of their vehicle.<a href="http://www.tirerack.com/tires/tiretech/tiretech.jsp" target="_blank">More Tire Tech Information</a>Related Links:<a href="http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=7" target="_blank">Calculating Approximate Tire Dimensions</a><a href="http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=10" target="_blank">Contact Patch</a><a href="http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=25" target="_blank">Plus Size Wheels and Tires</a><a href="http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=45" target="_blank">Tire Size Conversion Chart</a><a href="http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=46" target="_blank">Tire Size Guide</a>-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------In the tire industry, there are certain abbreviations that are used frequently and often those of us in the business forget that not everyone we talk to knows what all of the jargon means.For example O.E. stands for Original Equipment and Ser. Des. means service description.Other abbreviations associated with tires include:<ul> <li data-xf-list-type="ul">PSI = pounds per square inch</li> <li data-xf-list-type="ul">AS = all-season</li> <li data-xf-list-type="ul">M+S = mud and snow</li> <li data-xf-list-type="ul">SL = standard load</li> <li data-xf-list-type="ul">ASY = asymetrical tread design</li> <li data-xf-list-type="ul"><a href="http://www.tirerack.com/a.jsp?a=TX7&url=/tires/tiretech/techpage.jsp&techid=35&&bPostID=post-id-1b136c33-7abf-488e-a95e-b5b346f19695" target="_blank">ZR = Z speed rating (149+) and radial construction</a></li> <li data-xf-list-type="ul">TPMS = tire pressure monitor system</li> <li data-xf-list-type="ul">WS = white sidewall stripe</li> </ul>The list can go on on from here, but these are some of the more common abbreviations used in the tire industry.<ul> <li data-xf-list-type="ul"><a href="http://www.tirerack.com/a.jsp?a=TX7&url=/tires/tiretech/techpage.jsp&techid=56&bPostID=post-id-1b136c33-7abf-488e-a95e-b5b346f19695" target="_blank">ROF = run on flat </a></li> <li data-xf-list-type="ul">RF = reinforced sidewall</li> <li data-xf-list-type="ul">OWL = outlined white letter</li> <li data-xf-list-type="ul"><a href="http://www.tirerack.com/a.jsp?a=TX7&url=/tires/tiretech/techpage.jsp&techid=48&bPostID=post-id-1b136c33-7abf-488e-a95e-b5b346f19695" target="_blank">UTQG = uniform tire quality grade</a></li> <li data-xf-list-type="ul">OD = overall diameter</li> <li data-xf-list-type="ul">Snowflake M+S = severe duty mud and snow</li> </ul></blockquote>