Commercial vehicle tyres have two main types of markings on their sidewalls in addition to the manufacturer's own marks.
Tyre size markings on commercial tyres
Tyre size markings include references to the following information:
- The section width of the tyre (either in inches of millimetres).
- There is often an optional reference to the 'aspect ratio' of the tyre - that is a ratio of the tyre's height compared to its width.
- The types of tyre construction - 'R' for radial.
- The wheel rim diameter in inches.
Load and speed markings on commercial tyres
These inter-related markings are always shown together. They are known as the 'Load Index' and the 'Speed Rating Symbol', and reference the following information:
- Load index is a numerical code which shows the maximum load a single tyre can carry at the speed shown by it Speed Rating Symbol.
- There is often an optional reference which shows the load a twinned pair of tyres can carry at the speed shown by it Speed Rating Symbol.
-The Speed Rating Symbol indicates the speed at which the tyre can carry a load shown by the Load Index.