Tire speed rating or tire speed index/symbol specifies the top speed the tire can sustain when properly inflated, under service conditions specified by the tire manufacturer.
The speed rating is identified as a part of the tire size designation or the tire's service description, together with the tire 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 "T" defines the maximum speed limit at 190 kmph/118 mph (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 kmph/149 mph. Tires having a maximum speed capability above 300 km/h (186 mph) must have "Z" in the tire size designation and the service description must include Y in parenthesis (i.e., P275/40ZR17 93(Y)).
Tire speed ratings
|Speed Symbol||Speed (kmph)||Speed (mph)|
|(Y)||ZR**||Above 300||Above 186 (consult manufacturer)|
* 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.
Please note that the chart data should be verified with the tire/wheel manufacturer. This is for informative purposes only. The tyresizecalculator.com is not responsible for any errors that may arise with its usage.
This chart complements our website's Tire speed rating/symbol calculator.
See the Load index chart.