Tire speed rating or the speed index/symbol specify the top speed at which the tire can carry a load corresponding to its load index, under service conditions specified by the manufacturer.
The speed rating is identified as a part of the tire size designation or the tire’s service description, together with the load index.
The speed rating system as it is used today was developed in Europe as a response to the need for classifying tires into standardized speeds. It describes the top speed for which a tire is certified.
Speed rating on tires is expressed by a letter from A to Z (the speed symbol), ranging from 5 km/h (3 mph) to above 300 km/h (186 mph). For e.g. the letter "V" defines the maximum speed limit at 149mph/240 kph (Please see the tire speed rating chart below).
A tire rated with the letter "Z" in the tire size designation (i.e. P275/40ZR17 93W or 275/40ZR17 93Y) is the tire which have a maximum speed capability above 240 kph/149mph. Tires having a maximum speed capability above 300 km/h (186 mph) must have "Z" in the size designation and the service description must include Y in parenthesis (i.e. P275/40ZR17 (93Y)).
Tire Speed Ratings Chart
Please note that the chart data should be verified with the tire/wheel manufacturer. This is for informative purposes only.
|Speed Symbol||Speed (mph)||Speed (km/h)|
|(Y) ZR**||Above 186 (consult manufacturer)||Above 300|
* Tire manufacturer may or may not (is not obligated to) include a "Z" in the size designation.
** Tire manufacturer must include a "Z" in the size designation.