TYRE CODES

Have you ever wondered what the numbers on your tyres’ side walls actually mean? Well, wonder no more. A sporty rear motorcycle tyre might be marked 200/55 ZR17 M/C (78W). The first number is the tyre’s section width, which on this example is 200mm. The 55 is the tyre’s height as a percentage of the width, so here 55% of 200mm or 110mm (manufacturers are allowed +/- 4% variation). The Z is the tyre’s speed rating, in this case Z means over 150mph, while the R states it is a radial construction. The 17 indicates its is a 17in diameter tyre and M/C means it is for use on a motorcycle. Finally, the 78W is the tyre’s load and speed index, which is this case is 425kg at 168mph, taken from a predefined load index table.