Before you buy tires online or buy tires from your local tire dealer visit the U.S Department of  Transportation National Highway Traffic Safety Administration has a very informative site online that provides a complete overview on tire safety. Read about tire pressure, load limits, tire letter rating, tire speed ratings, tire size, tire tread, tire rotation, tire balance & wheel alignment, treadwear grade, treadwear number, tire temperature grade, U.S DOT Tire indentification numbers, steps to maintain proper tire pressure as well as other useful tire information. Before you buy tires online  Click here to visit their site and become more informed about tires and tire safety.