Load ratings are expressed in a pair of three-digit numbers, such as 125/122. “125” denotes that each tire can carry 3,638 pounds at the maximum inflation pressure. The second number (122) refers to the load rating on a single tire in a dual-rear-wheel application. A letter such as “Q” refers to the tire’s speed rating. In this case, the tire is rated at 99 mph for continuous use. The higher the letter, the faster the tire is rated to travel.