If you want to know more about your tyres, you need to decode what is written on its side. Check your car manual to know which type of tyres are compatible with your car.
The sidewall marking represent the following things:
235 (Width) The width of the tyre in millimetres.
55 (profile): Height of the tyre sidewalls as a percentage of the width.
R: (radial):This means the type of tyre. Other letters you may see are ZR, indicating that the tyre is for high speeds or RF which indicates that it is a run flat tyre.
17: (Diameter): 17 is the diameter of the tyre’s inner rim. It is always expressed in inches. The number varies between 10 and 23 inches for passenger vehicles.
99 (Load Index): This is an index of the maximum load carrying capacity per tyre at the speed designated by the speed symbol.
5 (speed index): The last letter indicates the maximum speed for the tyre at full load. W corresponds to a maximum speed of 270 km/h. This should generally be higher than your vehicles maximum speed, however, there are exceptions for winter tyres and exemptions in some countries.
