View Here : Tire Size Meaning
Locate your tire size on the sidewall of the tire (see picture above). The first number(16.9) represents the tire width sidewall to sidewall in inches. The second number(30) represents the rim diameter in inches.
Prior to 1964, tires were all made to a 90% aspect ratio. Tire size was specified as the tire width in inches and the diameter in inches - for example 6.50-15. From 1965 to the early 70's, tires were made to an 80% aspect ratio. Tire size was again specified by width in inches and diameter in inches.