A W speed rating on a tire indicates that the manufacturer produced the tire for use on exotic sports cars. The W rating gives the tire a maximum speed capacity of 168 miles per hour.
A tire's speed rating identifies the highest speed a vehicle should reach. A Y rating, for example, means that the tire can handle speeds up to 186 miles per hour. A tire can reach speeds above the designated maximum, but driving at speeds faster than the tire's tested limit is dangerous and may prevent the tire from performing optimally. A driver can find a tire's speed rating on the tire's size code. It is typically the last symbol in the sequence.