Sidewall markings

Tire size is the most important information given on the tire. The size designation is specified as a series of numbers and letters, for example, 185/65 R 14 86 T, where:

185 is the width of the tire in mm
65 is the aspect ratio (height to width ratio)
R denotes radial construction
14 is the rim diameter in inches
86 is the load index
T is the speed rating

The speed rating shows the maximum continuous driving speed capability of the tire. The speed rating to be selected depends on the make and model of car. The use of tires with speed ratings that are too low can affect the driving qualities and tires with speed ratings that are too high may reduce driving comfort.

The most important speed ratings are

Q = 160 km/h
S = 180 km/h
T = 190 km/h
H = 210 km/h
V = 240 km/h
W = 270 km/h
Y = 300 km/h