Speed index (SI) is one of the most important indformations on the side wall (next to the size and load index). The load index is marked by letter - A1-Y
Speed index determines the maximum speed, allowed for the given type of tyres. It must match specification of the vehicle’s producer and load index. Driving with the higher speed, than is marked on your tyre may lead to serious accident.
It is forbidden to fit tyre with the lower speed index, than it's recommended by the manufacturer. This rule refers, in particular to the summer tyres. Remember that load index is carefully selected by the manufacturer.
ATTENTION! Speed index can not be higher than recommended more than 2 levels. When you are changing the load index, you should put on your car an appropriate sticker!
Tool "speed index" contains the tabel, which shows the meanigs of the particular symbols.