You can find many useful information on the sidewall of your tire. At the end of the sequence, you can find a letter - in this case a W - which is the speed rating indication.
For example, a W speed rating means the tire can go up to a maximum speed of 168 miles per hour (270 kilometers per hour). The tire maximum speed can be determined by looking at the speed rating letter on the sidewall and see what speed it is associated with, using the table below.
The speed rating is typically found right after the load rating, following the tire size.