By Dan Miller
Progressive Farmer Senior Editor
The archenemy of ag tires is stubble. Brad Harris, manager of the field engineering group at Firestone, says corn and cotton stubble inflict the worst wear on agricultural tires.
Downtime because of a cut tire is costly, too. Harris, who farms in Ohio, says Firestone has calculated that downtime during the season’s optimal planting window (assuming an idle tractor hooked to a 16-row planter) may cost $570 per hour because of yield loss.
Firestone offered DTN/The Progressive Farmer a tour of its Firestone Farm Tire Test Center, at Columbiana, Ohio, about an hour northwest of Pittsburg. The 300-acre farm is where Harvey Firestone grew up and is the location today where engineers validate tire designs and test materials used to manufacture agricultural tires.
Newly designed tires go to Columbiana to die—on purpose. New designs are cut, sliced, blown up and generally abused in any number of ways. Firestone’s test center can replicate five years of heavy use in three to four months.
“Before a tire ends up on your farm, it’s got to go through the Firestone farm first,” Harris says. “We don’t want customers to go down in the middle of the field,” especially when tire replacement costs $2,000 to $5,000.
The Firestone test center sports more than a few ways to test tires. A pair of circular tracks paved with various surfaces tests tires mounted onto an overloaded and driverless tractor—the tractor tethered to the center of the circle. Track tests may run 1,600 hours to simulate extreme wear and tear.
The drum test applies loads up to 50,000 pounds on tires while exposing them to clouds of rubber-aging ozone to simulate damage from sunlight. Plunger tests evaluate material strength and resistance to puncture.
LASER VIEWER. One building houses a large, heavy steel cylinder in which tires are examined in a vacuum by lasers measuring minute variances in shape and wear not visible to the human eye.
Firestone’s one-of-a-kind “Mean Machine” is a 30-ton beast that can exert 34,000 pounds of drawbar pull, enough to stop a tractor in its tracks. Loaded with an array of diagnostics equipment, the Mean Machine mimics traction, drawbar pull, tire slip, rim slip, strength and durability.
Stubble is a production-crippling hazard for tires. Today’s corn, cotton and soybean plants are engineered to be strong and to stand up against wind, insect and disease damage.
Tires face two hazards from stubble. First is stubble piercing, when stubble punctures the tire, causing air loss. Second is stubble erosion. That occurs, as the name implies, over time. The stubble gradually wears through the tire treads to expose the radial cords.
There are ways to fend off stubble damage, Harris explains. Driving at an angle to the row, not directly down the row, is one. Another is tread design. Firestone manufactures tires with a “stubble deflector” tread design—the tread pattern pushes the stubble aside similar to a cowcatcher on a train.
DON’T GUESS. A second tire killer is improper inflation. Inflation pressure must match load. “Guessing is wrong,” Harris says. A $10 to $15 air pressure gauge can save many tires. Low pressure, without consideration for load, will rapidly damage the sidewall of a tire.
Air pressure changes by environment—for example, a slippery and muddy field versus a dry road surface with the tires turning at speeds up to 40 mph. High-clearance sprayers run on 17-inch tires inflated to 64 psi to carry 60,000 pounds. Larger planters will transfer 10,000 pounds to the rear of the tractor going from field to road.
“We need to know two things: tire size and the axle load,” Harris says. “Then, we can use inflation tables or the Firestone Tire Pressure Calculator [firestoneag.com]. Type in those numbers, and you’ll get the correct minimum inflation pressure to carry load.”
Sometimes, the operator will need several inflation calculations for the same piece of equipment because of changes in use and configuration, Harris adds. For example, carrying a three-point tillage tool. Running a tractor on duals all year, or not. These change air pressure requirements. “In all those cases, we need to know how many tires and what those axle loads are,” Harris says.
Firestone offers seven ideas for extending the life of agricultural tires.
1. Check tire pressure with a calibrated gauge. Set the inflation pressure using a pressure calculator such as Firestone’s Tire Pressure Calculator. Inscribe the correct inflation pressure in permanent marker near the inflation valve. Check tire pressures daily during the planting, growing and harvest seasons.
2. Check the sidewalls for cracks, cuts and other damage. Unlike a human cut, a tire doesn’t heal itself. If you see cords, it is time for a new tire.
3. Consider replacing a tire if there is less than 20% of the tread left. Worn tires slip and lose efficiency.
4. Complete a thorough tire check in the off-season. A 15- to 30-minute check in the winter can prevent costly downtime during the planting season.
5. Check ground contact area to make sure there is no gap between the tire lugs and the ground.
6. Check valve stems for cracks, corrosion and debris. Make sure valve caps are clean and intact.
7. Check all nuts and bolts to ensure they are torqued correctly.
Harris added an eighth tip. During work seasons, check the pressure of your tires daily.
Dan Miller can be reached at firstname.lastname@example.org
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