The 97w on a tire's size designation stands for the load index and speed rating. The load index is a number that corresponds to the maximum weight that the tire can support when properly inflated. The speed rating is a letter code that corresponds to the maximum speed at which the tire can be driven safely.
The load index of 97 corresponds to a maximum weight of 1,709 pounds (771 kilograms). The speed rating of W indicates that the tire can be driven at speeds up to 168 miles per hour (270 kilometers per hour).