Answer to age old question: tyres or tracks

Which is better for controlling compaction - tyres or tracks?

According to a report from the John Deere Company, results from a research study conducted by the Agricultural Engineering Department of Ohio State University has found that tyre inflation pressure makes all the difference in the compaction stakes. The compaction study focused on proper tractor weight and balance, the right tyre size, and the correct inflation pressures. The test looked at four different tractor set-ups, both with and without an implement (a 41-foot John Deere 980 Field Cultivator) attached to the draw bar.

The results ranked the four tractor set-ups from the lowest to highest compaction as follows:

  • 1 John Deere 8870 4WD Tractor with 710/ 70R38 dual radials correctly inflated (7 psi front and 6 psi rear);
  • 2 Caterpillar Challenger 75 with 35-inch belts;
  • 3 Caterpillar Challenger 65 with 25-inch belts;
  • 4 John Deere 8870 4WD Tractor with 710/ 70R38 duals overinflated (24 psi in all 8 tyres).

The tractor that finished first and last in the test was the same tractor. The only difference was the tyre inflation pressures. The conclusion was that the major contributor to compaction from a tractor with tyres is the inflation pressure, not simply the weight of the tractor. That's because the ground pressure under any tyre averages only 1 to 2 psi higher than the tyre inflation pressure, even when the tyre is under load.

There were statistically significant differences in the amount of compaction generated by each of the four tractor set-ups. The ranking remained the same for runs with the tractors pulling the field cultivator and runs without the implement.