Firestone, a manufacturer of this new class of farm tyres, recently hosted a field day for customers and dealers near Des Moines, Iowa, to demonstrate the benefits of the “next generation” in farm tyres. Firestone’s line is called AD2 (Advanced Deflection Design). The tyres are designed to carry more load at the same pressure or the same load at a lower pressure – or as much as 20% (Increased Flex -IF) or 40% (Very High Flex -VF) more load at the same pressure – as equivalent sized standard radial tyres.
Engineers set up two tractors for the field demo – a John Deere 8335R fitted with IF420/85R34 AD2 Radial All Traction DT TL R-1W tyres on the front and IF480/80R50 AD2 Radial Deep Tread 230 TL R-1W tyres on the rear. A John Deere 8310R was fitted with 420/85R34 Radial All Traction tyres DT TL R-1W on the front and 480/80R50 Radial Deep Tread 230 TL R-1W on the rear. “This demo is not a horsepower or fuel efficiency test,” noted Wayne Birkenholz, Firestone manager of field engineering.
He said the hypothesis for the test is “a tractor fitted with properly inflated AD2 tyres will reach the end of a measured course before an equally ballasted tractor fitted with properly inflated standard tyres of the same size, pulling an equal load.” FLEX DESIGN: This AD2 tyre was inflated to only 10 psi and pulled ahead of the tractor with the standard tyres inflated to the minimum required to carry the load. Here’s how the traction demonstration was set up. One end of a cable was attached to one drive tractor, run through a pulley on the “anchor” tractor and attached to the second drive tractor.
As both drive tractors pulled the anchor tractor at the same speed and rpm, the tractor with tyres delivering more traction moved ahead of the other. Birkenholz ran two demos for the group. Objective of the first demonstration was to show the importance of properly inflating a tyre to match the load. “Over inflation of tyres is a common occurrence,” he notes. LARGER FOOTPRINT: These side-by-side graphics demonstrate the larger tyre footprint achieved with lower tyre inflation pressures. The tyre inflated to 30 psi had a footprint length of 22 inches while the tyre inflated to only 14 psi had a footprint of 25 inches.
Tyres on the first tractor were set at 14 psi, which was the correct pressure for the load. The second tractor’s tyres were over inflated to 30 psi. Both tractors ran in 7th gear at 2,000 rpm, or about 3.5 mph with front axles engaged and the differential locked. Both tractors stopped simultaneously when the first tractor’s rear wheels reached the finish line. Then the distance between the rear axles was measured. The tractor with tyres properly inflated travelled 48.5 feet further on the 1,000-foot course. “In other words, the tractor with tyres inflated to match the load had 4.8% better traction,” explained Birkenholz.
The objective of the second demonstration was to show the difference in traction between Firestone’s AD2 radial and Firestone’s standard radial. Matching the load to inflation pressure the AD2 tyres were set at 10 psi. The same size Firestone standard radial tyres were set at 14 psi. Again, the tractors ran in 7th gear at 2,000 rpm or about 3.5 mph with front axles engaged and the differential locked. At the finish line the tractor with the AD2 tyres travelled 11.5 feet further on the 1,000 foot course or about 1.2% traction advantage. “Soil type and moisture can have an effect on efficiency,” said Berkenholz. “Typically, we see a 3-5% gain at this rate.” Firestone’s AD2 brand tyres are designed to be used on tractors, sprayers, implements and harvesting equipment.