Tires can be a bit of a trick considering there are two different readings you need to familiarize yourself with. Manufacturers like to bounce back and forth with almost no pattern. For someone trying to learn this can be quite frustrating. Not to worry though, both are very easy to follow and are simply the metric and standard version of tire sizing.
Metric: Obviously, the metric system is taking over and most tires today use the metric system to declare their sizing. A typical tire measurement for a Tacoma would read out as 195/75R14. The first number we see in the measurement refers to the width of the tire; in this case the tire is 195mm wide.
The next measurement refers to the sidewall. Here we find that the sidewall of the tire is 75% of the width of the tire. The final number tells you the rim the tire will fit on and for this example, the tire fits on a 14-inch rim. To find the overall height of the tire, you need to do some math. You need to find 75% of 195mm, multiply it by two, convert it to inches and then add that measurement to the rim size and you will get the height of the tire. In this case, the formula would look something like this:
- 195 x 0.75= 146.25
- 146.25 x 2 = 292.5
- 11.5 14= 25.5
In this particular example, the overall tire height is 25.5 inches. You can go through the runaround and find the measurement the long way around or you could use a tire size conversion calculator. Love it or hate it, this is the most common method used for declaring tire sizing.
Standard: Luckily for all of us, there are still standard measurements used for declaring tire sizes. A standard measurement would look something like this: 31x10.5R15. The first number tells us how tall the tire is in inches. In this case, the tire is 31 inches tall. The next number tells us how wide the tire is. Here we find the tire is 10.5 inches wide. The final number, of course, tells us how big the rim is, and this time the rim is 15 inches. Why would they ever abandon this method?