Tire sizing uses a cryptic formula that is really pretty easy to understand after you throw a little math
at it. The tire size in your question is a 215/70/14. This means that
the tire's widest point (outer sidewall to inner sidewall) is 215
millimeters wide. To convert this to inches, divide by 25.4 (=8.4645).
The 70 in the size is called the "aspect ratio". This is a percentage
of the tire's width. 70% of 8.4645 is 5.92515 inches. This number will
reflect the height of the tire's sidewall from rim
to tread. Because the tire is both above and below the rim, we have to
double that amount. This will give you 11.8503 inches of total
sidewall (let's round that number to 11.85 inches). The 14 in the tire size is the diameter of the rim. Add the
rim size to the total sidewall height (11.85 + 14 = 25.85), and you
have a tire with a diameter of 25.85 inches.
at it. The tire size in your question is a 215/70/14. This means that
the tire's widest point (outer sidewall to inner sidewall) is 215
millimeters wide. To convert this to inches, divide by 25.4 (=8.4645).
The 70 in the size is called the "aspect ratio". This is a percentage
of the tire's width. 70% of 8.4645 is 5.92515 inches. This number will
reflect the height of the tire's sidewall from rim
to tread. Because the tire is both above and below the rim, we have to
double that amount. This will give you 11.8503 inches of total
sidewall (let's round that number to 11.85 inches). The 14 in the tire size is the diameter of the rim. Add the
rim size to the total sidewall height (11.85 + 14 = 25.85), and you
have a tire with a diameter of 25.85 inches.
