The speed rating of any tire is a measurement of the top safe speed the tire can carry a load under specified conditions. It is also an indication of how the tire will handle at lower speeds. A higher rated tire will give you better traction and improved steering response – even at 50mph. You will find this rating on the sidewall of your tire, as part of the tire sizing number.

Maximum Speed Rating
Q = 99 MPH, 160km/h
R = 106 MPH, 170km/h
S = 112 MPH, 180km/h
T = 118 MPH, 190km/h
U = 124 MPH, 200km/h
H = 130 MPH, 210km/h
V = 149 MPH, 240km/h
Z = 149 MPH, 240km/h and over
W = 168 MPH, 270km/h
Y = 186 MPH, 300km/h