Load Index Rating
The majority of Tyres carry coded markings on them, which correspond to their load carrying and maximum speed capabilities. The load index is a numerical code associated with the maximum load a Tyre can carry (see table) at the speed indicated by its speed symbol (see Speed Ratings table) under service conditions specified by the tyre manufacturer.
For example, 91 = Load Index (91 equates to a weight of approximately 615 kg).
All Tyres must have a service description (i.e. load index and speed index) If the vehicle was to operate outside the service description indicated on the sidewall e.g. at a higher speed or overloaded then the Tyres would be deemed to be unsuitable for the use, and a prosecution could follow.