Tire-load range guides exist online at TireRack.com, WorkTruckOnline.com, TownFairTire.com and DiscountTire.com, as of 2015. The sites offer guides and charts for tires for passenger cars, light trucks and service trailers.
The load range for passenger tires comes in three simple degrees: light, standard and extra, which are rated at 35, 35 and 41 pounds per square inch, respectively. For light trucks, a tire's ply rating is also important, and load ranges change from words to letters: B is the lightest, and F is the heaviest, both in ply rating and load pressure. The service trailer ratings run in line with light trucks.