If you have an older motorbike, you may be having difficulty finding the right dimensions to replace your tyre, as the nomenclature has changed over time. Originally in inches, the tyre dimensions have now become standardised in millimetres (with the exception of the rim diameter which has remained in inches).
Fortunately, you can find compatible dimensions.
Here's how:
Motorcycle tyre size compatibility
You can find the correspondence between the dimensions in inches and the dimensions in millimetres in this table: