Definition: On the sidewall of every tire is information about tire size, maximum load rating, maximum inflation pressure, tire construction (See Radial Tire) and performance standards. Treadwear is a comparative rating of how long the tire will last compared to other tires. The higher the number, the longer the predicted life of the tread. A tire with a 200 rating should go twice as many miles as one with a 100 rating.Related Terms – Aspect Ratio- Radial Runout- Radial Tire- Speed rating- Wheel AlignmentThe numbers do not correspond to a fixed mileage figure because there are so many variables that affect the life of the tread (maintaining the correct inflation pressure is one of the most important). The traction rating is a measure of the tires ability to stop on wet pavement. An “A” is the best rating, “B” is average, and “C” is the lowest acceptable rating. The temperature rating is an indication of how cool the tire runs as highway speeds. Again, an “A” is the best while “C” is the lowest acceptable rating. Performance tires also carry a speed rating: “H” rated tires are good for speeds up to 130 mph, and “V” rated tires are certified for speeds above 130 mph. News source: About Auto Repair Old System:205/60VR15 New System:205/60R1591V 205 = Section width in millimeters 205 = Section width in millimeters 60 = Aspect ratio 60 = Aspect ratio V = Speed rating (unlimited V) R = Radial construction R = Radial construction 15 = Rim diameter in inches 15 = Rim diameter in inches 91 = Load index* V = Speed symbol (limited V)* Note: Always consult the manufacturer for the maximum speed of Unlimited V and Z tires. Speed rating is identified as a part of the tire’s sizing or service description (see above). * In the latest attempt to standardize tire designations, all ratings except unlimited VR and ZR incorporate the speed symbol and load index as the tire’s service description. “ZR” Rated TiresWhen “ZR” appears in the size designation with the service description, the maximum speed is as indicated by the service description.Tire Designation Maximum Speed P275/40ZR17 93W 270 km/h (168 mph) P275/40ZR17 93Y 300 km/h (186 mph) For tires having a maximum speed capability above 240 km/h (149 mph), a “ZR” may appear in the size designation. For tires having a maximum speed capability above 300 km/h (186 mph), a “ZR” must appear in the size designation. Consult tire manufacturer for maximum speed when there is no service description.Speed Symbols SpeedSymbol Speed(km/h) Speed(mph) SpeedSymbol Speed(km/h) Speed(mph) A1 5 3 K 110 68 A2 10 6 L 120 75 A3 15 9 M 130 81 A4 20 12 N 140 87 A5 25 16 P 150 94 A6 30 19 Q 160 100 A7 35 22 R 170 106 A8 40 25 S 180 112 B 50 31 T 190 118 C 60 37 U 200 124 D 65 40 H 210 130 E 70 43 V* above 210 above 130 F 80 50 V 240 149 G 90 56 W 270 168 J 100 62 Y 300 186 above 300 above 186 * For Unlimited V tires without the Service Description, the speed category is over 210 km/h (130 mph).