We get many questions about what the numbers on the side of your golf cart tires actually mean. For standard (American) sizes, it’s pretty straight forward and we also cover this topic on our article, “All You Ever Wanted to Know About Tires & Wheels”. The non-standard (foreign/metric) sizes are a bit more complex to decipher. We will touch on both within this article.
We’ll start with the standard American sizes that most of us are familiar with. An example would be the most common golf cart tires size in the world, which is 18×8.5-8, and all sizes are in inches. Each number within this size represents a dimension. The first number (18 = A) represents the overall height of that tire when mounted and inflated. The second number (8.5 = B) represents the width of the inflated and mounted tire. And the last number (8 = C) represents the hole inside of the tire where the wheel goes. This number is also said to be your wheel size. See diagram to the right. In this example, the sidewall is a simple math problem. Subtract the wheel size from the overall height of the tire and then divide by 2 since half of the sidewall height is above and half is below the wheel.
Example 1 – Standard Sizes: 18 (Height) – 8 (Wheel) = 10 Inches / 2 = 5 Inches of sidewall.
This statement represents that if you measure from the edge of the wheel outward to the tread, you should measure approximately 5 inches of sidewall on your golf cart tires.
Now we’ll move on to our more complex metric/foreign examples. The same diagram can still represent the dimensions except that are in a different order AND one of the measurements thereof is still in inches.
Let’s take a low profile tire as an example. As the name implies, these golf cart tires typically have a much larger wheel within the center and have a much smaller sidewall profile. For an example, we’ll use 205/30-14. Keep in mind for all of these calculations that there are 25.4 mm per inch for conversion purposes.
In this example, the first number (205) represents the tread width (B) in millimeters and 205 mm equals approximately 8.07 inches wide. The second number (30) represents the percentage of the tread width used for the sidewall calculation. In this case, that would be 30%. We’ll get back to that number in a moment to calculate the overall height & sidewall. The third number (14) represents the wheel size/ size of the tire hole (C) in inches.
In this example, the 205mm converts to 8.07 inches. Thirty percent of 8.07 inches is 2.42 inches, which is the sidewall profile. Remember that you have that amount of side wall both above and below the wheel, so to determine the overall height, multiply the sidewall profile by 2 and then add to the wheel size.
Example 2 – Metric Sizes: 205/30-14
205 mm = 8.07 inches;
8.07 inches x 30% = 2.42 inches of sidewall;
2.42 inches of sidewall x 2 = 4.84 inches;
4.84 inches + 14 inches (wheel size) = 18.84 inches
In this example for planning purposes, I would advise customers that these golf cart tires are actually 19 inches tall to allow for a bit of over inflation just in case. A 19 inch tall tire will fit many, but not all non-lifted golf carts. There are, of course some exceptions on golf carts where the wheel well clearance is more limited and cannot accept this size without rubbing issues.
By Michael Williams