What Do The Numbers Mean?
A: Width (120/80-19)
Width of the tire, typically in millimeters, from sidewall across the tread to the opposite sidewall.
B: Aspect Ratio (120/80-19)
The height of the cross-sectional profile expressed as a % of the width of the tire
C: Rim Size (120/80-19)
The third number is the diameter of the wheel in inches.
Example: 120/80-19 or A/B-C [ The width(A) of the tire is 120mm. The sidewall height(B) is 80% of 120 or 96mm. And it fits a 19in wheel(C) ]

