Properly inflate tires for optimum performance

SHERIDAN, Ill. — The air inside a tire carries the load of a tractor, implement or vehicle, not the structure of the tire.

“A tire is basically a pressure vessel designed to contain a volume of air required to support a specific load,” said Joe Woodward, original equipment and strategic accounts senior manager for Firestone Ag.

“If you don’t inflate the tire, the structure is not going to carry the load,” said Woodward during a presentation at the Firestone Ag Rock the Crop event at Spirit Farms, owned by John and Michelle Stewart.

“The air and structure have a partnership to do what you need a tire to do,” he said. “Tires transmit torque from the vehicle drive train to the ground.”

Agricultural tires are designed to operate at a specific level of deflection.

“That determines its various performance characteristics such as durability, footprint size and ride quality,” Woodward said. “A properly inflated tire helps give you the best ride.”

The appropriate inflation pressure for a specific application is determined by the axle load and the size of the tire.

“The larger the air cavity, the more load a tire can carry,” the senior manager said.

“A lot of people think the bottom half of the tire is carrying the load,” Woodward said. “It does carry some, but with a radial tire, most of the load is being carried by the top half of the tire.”

“When we don’t inflate enough, we ask the tire structure to do more than it was designed to do,” he said. “That’s when we start to have issues in the field like poor wear or a sidewall buckle.”

Bias tires have plies with a crisscross pattern and the plies for radial tires are at 90 degrees.

“Radial tires demonstrate superior mechanical function to bias tires for just about everything,” Woodward said.

Firestone Ag has a team of scientists and engineers to design the components of tires to do exactly what they need to do.

“There could be up to 18 different types of rubber with different functions based on where they are,” the senior manager said. “The inner liner is designed to do one thing — prevent air from permeating through it.”

A proper tire setup, Woodward said, helps to increase efficiencies, saves fuel, saves time and helps farmers get the best investment out of their ag tires.

Firestone Ag has a six-step procedure for proper tractor set up — identify the horsepower of the tractor, calculate the required weight based on the tractor type, calculate the weight split by the tractor type, weigh the tractor to determine the actual axle loads, remove or add weight as needed and set the inflation pressures based on the axle loads.

“Our company makes recommendations of what your total tractor weight should be per PTO horsepower,” the senior manager said. “We recommend a 60-40 rear to front weight split for 3-point work because 3-point work typically puts more load on the rear axle.”

Operating tires at a proper inflation pressure will maximize traction because it increases the footprint and reduces wheel slip, Woodward said.

“Overinflation decreases the length of the footprint, can lead to reduced traction which can increase fuel consumption and there could be poor wear performance or poor ride quality,” he said.

The Ohio State University conducted a study with tire inflations of 24 or 14.

“They saw fuel usage differences from 5% up to 26.5%,” Woodward said. “By just inflating your tires properly, not only does it maintain the tire durability, it helps the efficiency of your operation.”

“If you put more inflation in the tire than you need, it will compact the soil,” he said. “If you have too much compaction, the root balls can’t expand, the plants will be less healthy and the yields will be lower.”

Tires get harder through use, Woodward said, but tire rubber is not designed to be harder than modern stubble.

“Crops have been engineered to deal with high winds so you don’t lose your crop and they are also engineered to carry heavier ears of corn,” he said. “The robust, hard stalk can wreak havoc on tires.”

Since the center part of the tire is most susceptible to stubble damage, diagonal tillage can be a problem, Woodward said.

“We advise going parallel to the rows and cutting your corn a little higher so the tire can knock it down,” he said.

For soybeans, it is better to cut them as low as possible, Woodward said.

“We advocate stubble mitigation devices,” he said.