What does 90/90-12 mean?
2 Answers
90/90-12 refers to a tire with a width of 90mm, an aspect ratio of 90%, meaning the radial thickness of the tire is 90x90% = 81mm, and a rim diameter of 12 inches. Additional information: 1. Labeling methods: There are two ways to label motorcycle tire specifications—one is the code notation method, and the other is the metric notation method. The code notation method uses "b-d" to represent the tire, where "b" is the tire's section width, "d" is the tire's inner diameter (also the rim diameter), both measured in inches, and the "-" in between indicates a low-pressure tire. 2. Tire pressure: The inflation pressure for motorcycle tires generally ranges between 147kPa and 343kPa. Sometimes, tire specifications may also include the ply rating at the end, such as 2.75-17-4PR, indicating a tire section width of 2.75 inches, an inner diameter of 17 inches, and a 4-ply rating for the tire's cord layers.
I frequently work on motorcycles, so when I see the numbers 90/90-12, I immediately recognize it as the tire size specification. Simply put, the first 90 refers to the tire width of 90 millimeters, which affects grip and stability when cornering; the second 90 indicates that the tire height is 90% of the width, meaning a height of approximately 81 millimeters, which determines ride comfort and absorbs minor vibrations; finally, the 12 is the rim diameter of 12 inches, which must match your bike's frame. This size is very common on small scooters or lightweight motorcycles, and ensuring the width is appropriate to avoid slipping is crucial. A tire that's too narrow or has a high aspect ratio poses significant risks on slippery roads. I personally check tire pressure and wear regularly to prevent accidents. If the specifications are incorrect, it can accelerate wear or even lead to loss of control, so I recommend carefully checking the owner's manual for the correct size when buying new tires and not skimping on quality by opting for cheaper options. The type of tire also affects performance—synthetic rubber is more durable.
