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sprayer Firestone
PUT TIRES ON CHECKLIST: How many times do you check tire pressure during the season? Engineers recommend checking it as often as you check engine oil.

Get full life from sprayer tires

Understanding the modern rating system can help you get the right tires to carry the load.

Your planter is ready to roll. Now it’s time to get your self-propelled sprayer ready. You check maintenance items related to the engine, evaluate valves and nozzles, and calibrate the sprayer. You will likely test precision equipment. Will you check the tires?

If you’re thinking, “Why would I do that?” you’re likely not alone. Thinking about tires on your sprayer probably isn’t high on your checklist. If it isn’t even on your list, Brad Harris says it should be. Harris is the manager of Firestone Ag Field Engineering.

“You need to have the right sprayer tires for your application, and run them at the correct pressure,” Harris says. “Otherwise, you could cause unnecessary wear on tires.”

Tire options
Hopefully, by working with your local equipment or tire dealer, you have the right tires for the capacity of your sprayer. Tire companies once talked about “ply ratings” for ag tires, but with most companies offering radial ag tires today, they typically rate tires by a term called “load index.” You will find the load index on the tire following its size description, Harris explains. Load index will also be listed in literature or specifications for the tire.

“We generally want sprayer tires with a load index of 160 to 168 if the sprayer is carrying an 800-gallon to 1,000-gallon sprayer tank,” Harris says. For example, Firestone offers an IF 380/90R46 tire with a load index of 168, he says. The carrying capacity for that tire is 12,300 pounds at 64 pounds per square inch pressure.

If your sprayer has a 1,250-gallon tank or larger, it should be running on tires with a higher load index. “Sprayers with tanks in the 1,200- to 1,600-gallon capacity would likely require tires with a load index rating in the 173 to 177 range,” Harris says.

Proper inflation pressure depends on the type of tires, he adds. If your sprayer is equipped with wider flotation tires, the recommendation is typically 35 to 46 psi.

“If you’re running narrow tires to get between the rows, the range will be 58 to 78 psi to carry the same load,” Harris says. “We need much higher inflation pressures than on tractor tires because we’re typically running singles, not duals, and the tires are narrow so we don’t knock over the crop.”

To find a tool that helps you determine the right size tire for your load, visit

The biggest part of maintenance is maintaining the proper tire pressure throughout the season, Harris says. Refer to your manual for proper tire inflation pressure. Then check the inflation pressure during preseason preparations and adjust accordingly.

“You need to get in the habit of checking tire pressure regularly during the season, just like you check engine oil level,” he says. “If tires are underinflated or overinflated, you’ll get uneven wear or early removals.

“The best way to get full life expectancy out of any tire is to monitor tire pressure frequently and maintain it at recommended levels for the load.”

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