Tire speed indices

Speed index (e.g. «T») after tire size marking (e.g. 185/65 R14 86T) indicates the allowed maximum speed (V_max) for this tire.

Tires for the corresponding vehicle must be selected so that their maximum permissible speed is greater than the maximum («design dependent») vehicle speed.

If in a particular case we are talking about a car that has a national operating permit, then the maximum speed of the car is calculated as follows.

Formula for cars with V_max up to 150 km/h.

V_max = 1.03 xv + 3.5 km/h.

Example: specified maximum speed V = 145 km/h.

V_max = 1.03 x 145 km/h + 3.5 km/h = 152.85 km/h.

In this case, you must use a bus with an index «ABOUT» or with a higher speed index.

Formula for cars with V_max from 151 km/h.

V_max = 1.01xv + 6.5 km/h.

Example: indicated maximum speed V = 163 km/h.

V_max = 1.01 x 163 km/h + 6.5 km/h = 171.13 km/h.

In this case, you must use a bus with an index «S» or with a higher speed index.

Vehicles with EU type approval.

In the case of a vehicle with EU type approval, the maximum speed is calculated for all vehicles using a formula.

V_max = 1,05 x v.

Example: indicated maximum speed V = 172 km/h.

V_max = 1.05 x 172 km/h = 180.60 km/h.

In this case, you must use a bus with an index «T» or with a higher speed index.

The use of tires with a higher speed index is allowed. The same applies to tires with a higher load index.

NOTE: Instead of a letter «V» you should substitute the maximum speed indicated in the vehicle passport in column 6. This conversion is necessary because all cars, for technical reasons, develop different maximum speeds within the legal tolerance.