For example, a tire graded 200 would wear twice as well on the course as a tire graded 100. The rating increases in 20-point increments. It is important to note that the true performance of a tire depends upon the actual conditions of its use.
Tires should be inspected at every opportunity; once a week isn't too often. Learning to read the early warning signs of trouble can prevent wear that shortens tire life or indicates the need for having other parts of the car serviced.