The speed rating of a tire indicates the speed category (or range of speeds) at which the tire can carry a load under specified service conditions. A letter from A to Z symbolizes a tire's certified speed rating, ranging from 5km/h (3 mph) to above 300 km/h (186 mph). The speed ratings for OTR tires and truck tires falls in the A to K range. Code A1 A2 A6 A8 B C D E F G J K Speed (km/h) 5 10 30 40 50 60 65 70 80 90 100 110 Speed (mph) 3 5 20 25 30 35 40 45 50 55 65 70