Hope this helps I don't have a metric measure to check.
Metric
Examples: 180/55ZR-17 · M130/80-18 · 130/80HB-18 · 130/80H-18
The Metric tire size system is the most common and also the most descriptive. Metric sized tires are used on just about every type of motorcycle, from the latest sport bikes, to cruisers, touring bikes and everything in between. An "M" sometimes precedes a metric size when there is no speed rating used. It simply means that it is a motorcycle tire. Another letter is sometimes used after the speed rating to indicate belted (B) or radial (R) tire construction.
In the first example above, 180 is the width in millimeters, 55 is the aspect ratio (cross-section height is 55% of the width), Z is the speed rating (149+ mph), R specifies it's a radial construction tire, and 17 is the wheel diameter in inches.