Dimension designation for tyre
The car has an approval for the complete vehicle with certain combinations of wheel rims and tyres.
Designation of dimensions
All tyres have a dimension designation, such as: 235/55 R18 104 V.
235 | Tyre width (mm) |
55 | Ratio between tyre wall height and tyre width (%) |
| R | Radial ply |
18 | Rim diameter in inches |
104 | Codes for the maximum permitted tyre load, tyre load index (LI) |
V | Speed rating for maximum permitted speed, speed rating (SS). (In this case 240 km/h (149 mph).) |
Load index
Each tyre has a certain capacity to carry a load, a load index (LI). The car's weight determines the load capacity required of the tyres.
Speed rating
Each tyre can withstand a certain maximum speed. Tyre speed rating, SS (Speed Symbol), must at least correspond with the car's top speed. The table below shows the maximum permitted speed for each speed rating (SS). The only exception to these regulations is winter tyres1, where a lower speed rating may be used. If such a tyre is chosen, the car must not be driven faster than the speed rating of the tyre (for example, class Q can be driven at a maximum of 160 km/h (100 mph).) The top speed at which the car can be driven depends on road conditions, not the speed rating of the tyres.
Note
| Q | 160 km/h (100 mph) (used only on winter tyres) |
| T | 190 km/h (118 mph) |
| H | 210 km/h (130 mph) |
| V | 240 km/h (149 mph) |
| W | 270 km/h (168 mph) |
| Y | 300 km/h (186 mph) |