How To Read a Tractor Tire Sidewall

Published on
December 11, 2020 12:12:00 AM PST December 11, 2020 12:12:00 AM PSTth, December 11, 2020 12:12:00 AM PST

If you need to switch out your tractors’ tires, then you’ll have to understand the options on the market. But before you make your purchase, you should learn some sizing terminology. Here’s a quick guide that’ll help you decode how to read a tractor tire sidewall.

Know Where To Look

First, if you want to find out a tire’s size, you must look at the sidewall, which is the innermost portion of your tire. Manufacturers brand important information onto their tires, and at first glance, you may just see a series of letters and numbers. However, these have meaning—they are your tires’ measurements. Traditional tire measurements are in inches, while metric tractor tires are in millimeters.

Decode the Size Measurements

Let’s talk numbers—you probably see two sets of numbers. The first number you’ll notice is the tire width from sidewall to sidewall. The width determines flotation; the wider your tire, the more likely it’ll have better traction in textured ground—for instance, in muddy soil and sand. The second number is the rim diameter, which notes whether a tire will fit a rim of a certain size. If you see three numbers, the first number will be the tire’s height, followed by its width and rim diameter.

We’ll provide you with an example. Let’s say you see 650/65R38—this would be the metric measurement. The first number, 650, would be the tire’s width in millimeters, and 65 is the aspect ratio from rim to tread. The last number, 38, is the rim diameter, meaning the tire fits a 38” wide rim. The imperial measurement here would be 24.5 x 38.

Other Pertinent Information To Know

The first letter you’ll see on your tire indicates the type of construction. Your tire’s sidewall also has a load index number, or weight carrying capacity; you’ll see two or three digits, and the higher the number, the larger the load the tire can carry. Additionally, you’ll see your tire’s speed rating, and this number is the maximum speed of the tire. This information includes a letter as well; “A” is the slowest, and as you continue in the alphabet, each letter indicates a gradual increase in speed.

Take 151A8 or 151/A8, for example—151 would be the load index, so a single tire can carry 7600 pounds. A8 is the speed rating, which means the tire’s speed is up to 25 mph.

It is important to add all the speed load ratings together from all the tires. And also to factor in the weight of the machine. The remainder will be the amount of carrying capacity you will have. If you typically carry more than what your tires are rated for, you may need to:

  • Upgrade to a thicker tire with more plys
  • Consider an IF or VF tire—both boast higher carrying capacities
  • Search for a CFO tire, which allow you to overload a tire as long as it’s for less than 50% of the time
  • Upgrade tire sizes.

You may even recognize a date code, too, and these codes state when and where your tire was made. You’ll see a letter code for the manufacturing location as well as the product batch code, which acts like a serial number. Then, you’ll find a series of numbers, which are the date. The first two numbers are the week, and the last two numbers are the year.

We’ll reference a Firestone as an example—if the manufacturing code is “VE012500 0220”, we can infer that VE refers to the manufacturing location, so in this case, the tire was manufactured in Des Moines, Iowa. Next, 012500 is the product batch code, 02 stands for the week of production (the 2nd week of the calendar year), and 20 is the year of production (2020).

Further, a bead seating warning is on your tire, and this aids you in inflating your tire to the correct maximum pressure. Lastly, tires should have safety warnings, so read these carefully.

Now that you’re a little more familiar with how to read a tractor tire sidewall, you can make the best purchasing decisions. Ready to buy? Dawson Tire & Wheel leads in agricultural and irrigation tires. We encourage you to browse our inventory now. Additionally, we offer wholesale tractor tires; if you’re interested in partnering with us, call us today.