HOW TO READ YOUR MOTORCYCLE TYRE’S SIDEWALL MARKINGS
Your Dunlop motorcycle tyre sidewall contains all the information about your tyre that you’ll need, but what does a number such as 120/70 ZR17 M/C (58W) actually mean? Here’s a little guide to understanding these markings:
1) TYRE WIDTH
This number indicates the tyre’s section nominal width, measured in millimeters from sidewall to sidewall. In this case 120mm. Note: the actual physical width of the tyre on the rim can differ from the nominal width.
2) ASPECT RATIO
This number indicates the tyre’s aspect ratio or height expressed as a percentage of its width. In this case the aspect ratio is 70% of the 120mm width, making it 84mm.
3) WHEEL DIAMETER
On a sports bike tyre these letters are usually “ZR”. The “Z” indicates the speed rating of the tyre, which in this case means it is rated above 240kph/149mph. The “R” denotes that the tyre is of radial type construction. The “17″ denotes that the tyre is 17 inches in diameter whilst “M/C” means the tyre is for a motorcycle.
4) LOAD INDEX & SPEED RATING
The ‘58W’ indicates the load and speed indexes of the tyre and should always be looked at together when you buy a new tyre. In this case the ’58’ denotes that the tyre is rated for a maximum carrying weight of 236kg at maximum pressure. The “W” represents the maximum speed for the tyre when it is correctly inflated and being used under load, in this case 270km/h. Please remember however that when buying new tyres that you match the speed rating with the speed capabilities of your motorcycle, if exceeded, this risks tyre failure, hence you should always replace a tyre with one of at least the same speed rating so that you don’t reduce the speed capability of your bike.
Please refer to the load index and speed rating tables for more information.