4.1.3. Indexes of speed of tires

The speed index (e.g. "T") after marking of the size of the tire (e.g. 185/65 R 14 86T) specifies the admissible maximum speed (vmax) for this tire.
Tires for the corresponding car need to be selected so that their most admissible speed was more maximum ("depending on a design ") car speeds.     
If in a concrete case it is about the car having interstate permission to operation, then the maximum speed of the car pays off as follows.
Formula for cars with Vmax to 150 km/h.
Vmax = 1,03'V + 3,5 km/h.
Example: the specified maximum speed of V = 145 km/h.     
Vmax = 1,03'145 km/h + 3,5 km/h = 152,85 km/h.
In this case it is necessary use the tire with the Q index or with higher index of speed.
Formula for cars with Vmax from 151 km/h.
Vmax = 1,01'V + 6,5 km/h.
Example: the specified maximum speed of V = 163 km/h
Vmax = 1,01'V163 of km/h + 6,5 km/h = 171,13 km/h.
In this case it is necessary use the tire with the S index or with higher index of speed.
Cars with standard permission of the EU.
If in a concrete case it is about the car with standard permission of the EU, then the maximum speed is calculated for all cars by a formula.
Vmax = 1,05'V.     
Example: the specified maximum speed of V = 172 km/h.     
Vmax = 1,05'V172 of km/h = 180,60 km/h.
In this case it is necessary use the tire with the T index or with higher index of speed.
Use of tires with higher index of speed is allowed. The same treats also tires with higher index of loading.

NOTE
Instead of the letter "v" it is necessary to substitute the maximum speed specified in the passport of the car in column 6. This transformation is necessary as all cars for technical reasons gather various maximum speeds within admissible laws of the admission.