The alphanumerical coding on the sidewall of Dunlop motorcycle tires can be confusing. It is important to understand these codes to ensure you are getting a safe tire that will work on your particular motorcycle.
Dunlop tire codes utilize metric measurements. Metric sizing is the most widely used and has the most information. Our example is a motorcycle tire sized at 180/65B16. We’ll get to the letters in a minute but here is what the individual numbers mean:
180 = the 180 designates the tire’s width in millimeters, measured in a straight line through the tire from one edge of the tire’s tread to the other.
65 = The second number, 65, is a bit trickier to understand. This represents the aspect ratio between the tire’s width and its height; or how tall a tire is in relationship to its width. Simply put, the higher this number is, the taller the tire will be. In this case, the tire is 65 percent as tall as its width.
16 = The last number, 16, is the tire’s rim diameter expressed in inches.
The letter(s) after the aspect ratio, in our case a “B”, indicates speed rating and/or tire construction. If there are two letters after the aspect ratio, the first will be speed rating and the second will be tire construction. The “B” stands for Bias Belted. You might see an “R” for Radial or a “D” for diagonal bias.
If there is only one letter or a dash (-) after the aspect ratio, then it indicates construction type and the speed rating will appear in the service description. The service description combines the load index (81) and the speed rating (H). The service description in our example size is “81H.” Please see the charts below for load index and speed ratings.
Other Tire Markings of Significance
Date of Manufacture
All Dunlop tires also specify the date of manufacture on the sidewall. It is important to pay attention to these dates as tires can become unsafe if they are stored too long or in poor storage conditions. On the side wall next to the U.S. DOT tire identification number you will find a 4-digit number. The first 2 digits indicate the week of its manufacture and the last two are for the year. In our example, the 0916 translates to the 9th week in the year 2016.
Rotation and Balance Marks
One of the more critical marks on a motorcycle tire is the rotation arrow(s). Today’s specialized motorcycle tires generally have a tread pattern that must go in only one direction. The other big reason for noting wheel direction has to do with the manufacturing process. The tread rubber is initially a flat strip cut to length, at an angle, then spliced together with the two ends overlapping, creating a hoop. Under acceleration, a tire mounted backward will try to peel back this splice. The opposite is true for the front wheel, where directional forces are reversed under hard braking.
In some cases, it is acceptable to use a rear application tire on the front, you just need to reverse the rotation - but never use a front application tire on the rear. (Always consult with your motorcycle manufacturer before reversing the rotation. The best policy is to always use a front motorcycle tire on the front and a rear motorcycle tire on the rear!)
Another mark to look for when mounting a tire is a painted balance dot, or dots. Most tires are pre-balanced by the manufacturer. They will then put a mark on the tire indicating where the valve stem should line up. This is a good practice but not critical and not always available on some tires. More critical is a good balance.
