Running the correct air pressure on your tires is very important.

Running at the correct air pressure will contribute to the lowest ground pressure, which will contribute to low compaction and improved crop yield; contribute to getting the most traction out of your tires, putting the biggest footprint on the ground and contribute to a nice ride, and contribute to getting the most tire life out of your tread.

 Let's use one of the most popular replacement AG tire sizes in use in the last 5 years: 460/85R38. The table below is for the subject size with a load index of 149 and a speed index of A8.

 Load Table

The first piece of information we need is how much weight each tire must carry. In the interest of time, we will say we have already made that calculation. The load the tire must carry equals 6,600 lbs. The next piece of information is: what is the maximum speed we will be traveling at? We will be using a speed of 20 mph. 

How many tires will be on each axle? Two, which would be a single application, or four, which would be a dual application. You could also have six tires on an axle, which would be triples. Our example will have two tires.

Our first step is to find the speed of the equipment in the SPEED column. Our speed is 20 mph. Shown by the red circle.

The next step is to move along the SPEED row until we find 6,600 lbs. Sometimes the load table does not have the exact weight we are trying to find. 6,640 is very close. My suggestion is to always go higher on the load. You never want to go lower because that would cause underinflation, one of the enemies of a tire. We will use 6,640. Shown by the blue circle.

We then move up that column until we intersect the PSI row. PSI stands for pounds per square inch. The measurement for air pressure. In our example, we would intersect the PSI row at 17. We would then recommend 17 psi be put in the tire. This air pressure will easily carry the 6,600 lb. load at 20 mph.

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