Modern Tire Dealer has partnered with AG Tire Talk to provide answers to insightful questions that farm tire dealers have about farm tire technology. This is the next installment in our ongoing series, which is designed to help farm tire dealers better connect with their customers. A trending question, followed by answers, will appear in our Commercial Tire Dealer section every other month. For complete answers, click on www.agtiretalk.com.
QUESTION: What are the benefits of using increased high flexion (IF) and very-high flexion (VF) tires?
Dave Paulk, manager, field technical services, BKT USA Inc.: IF and VF tires are becoming more commonplace in the market and are used on more equipment now than in past years. There are definite advantages in using IF/VF tires and applications where they work and perform much better than standard tires. Farms are more spread out. Farmers must get their tractors and equipment from one farm to the next by driving on the road. As equipment gets heavier, IF/VF tires are useful in carrying the weight of the equipment at highway speeds.
IF-rated tires are made to carry up to 20% more load at the same air pressure as a standard tire. They will carry higher loads at higher air pressures than standard tires. VF tires are made to carry 40% more load at the same air pressure as a standard tire. They can also carry heavier loads at higher air pressures.
When transporting equipment at highway speeds, oftentimes this higher load capacity is needed to keep the tires from failing because of heat buildup and overload. Most tractors will run at least 30 mph and most sprayers will run at 40 mph. Higher air pressures are needed when transporting on the road to carry the weight and keep the tires running cooler. In some cases, IF or VF tires must be used because of the heavy weight of the equipment.
Conversely, when used in the field, IF and VF tires can be run at less air pressure to minimize soil compaction, where no till and minimum till farming is concerned. They are being run at slower speeds. However, the tires must have enough air to carry the weight of the tractor and implements. Since air pressure determines ground bearing pressure, IF and VF tires can be run with 20% and 40%, respectively, less air pressure compared to a standard tire.
By running less air pressure in the field, the radial tire has a wider and longer footprint to help spread the weight of the tractor or equipment out over a wider area. This also offers better traction and more fuel savings in the field.
When central tire inflation systems are used, tires can be inflated for road use and deflated for field use. Low air pressures set for field use do not work on the highway. The faster a tire rolls, the less weight carrying capacity it has. Running low air pressures on the road allows tires to run hot and they don’t dissipate heat as easily. This will cause tires to eventually fail in the bead and sidewall areas. Conversely, running lower air pressures in the field will minimize soil compaction, give better traction and burn less fuel.
Some IF and VF tires may be labeled as IF or VF-CFO (cyclic field operation) tires. CFO tires are used mainly on combines and grain carts where the loads are cyclical or changing and are not constant. At slower speeds, these tires allow load bonuses for use in the field at slower field speeds. IF-CFO tires allow a 70% load bonus at up to 5 mph cyclic, a 55% load bonus at up to 10 mph cyclic and a 35% load bonus at up to 20 mph cyclic. VF-CFO tires allow a 48.5% load bonus at up to 5 mph cyclic, a 35.5% load bonus at up to 10 mph cyclic and a 13.5% load bonus at up to 20 mph cyclic.
At slower field speeds IF or VF-CFO designated tires will carry a lot of weight without having to adjust air pressures.
Greg Gilland, vice president, global agriculture, Maxam Tire North America Inc.: On average, agricultural tires tend to operate between 16 psi to 20 psi for mechanical front wheel drive or four-wheel drive tractors working in the field; about 25 psi for combine harvesters; and above 60 psi on self-propelled sprayers.
The development of IF and VF technology is allowing working air pressures to be lowered significantly, delivering improved performance and better crop yields. The structural design and capability of modern tires impact how much air pressure is required to carry the intended axle load.
All radial tire casing structures only carry 20% of the actual intended load, with the compressed air accounting for 80% of the carrying capacity. This is true in any radial tire application, from passenger vehicle tires to the largest giant OTR mining tires. The advent of IF and VF technology is rewriting the rules by giving the structural components a larger impact on the carrying capacity — transferring the axle load carrying responsibility away from the compressed air and increasing the weight-bearing function back to both the casing and rubber materials.
IF and VF tires are evolved products that use improved rubber compounds and higher tensile strength cables or chords to achieve the load, speed, heat resistance and endurance that can be demanded in their work applications or conditions.
Referring to VF tires with CFO, in most cases, the greatest enemy of a tire is the corresponding heat generation on the tire casing that occurs as machines get heavier, carry greater axle loads and operate faster. For example, the current transition in the market to larger combine harvesters evolving from Class 9 to Class 10 machinery, designed with greater horsepower, is increasing the demand or use of tires that can offer CFO capability.
In essence, a CFO-engineered tire — whether developed as a standard, IF or VF product — must be able to withstand continuous dynamic loads in the field. Specifically, CFO tires are working in repetitive cycles during the harvest season, with tire loads increasing and decreasing dramatically in a very quick period from light loads to heavy loads as the harvester works the field filling or emptying its on-board bin.
A CFO-rated tire therefore must be capable of flexing under extreme working conditions at specific air pressures without compromising performance, traction, productivity or soil compaction.
IF or VF tire technology provides the best viable solutions to cyclic field conditions as their construction materials have been engineered to provide the endurance, casing integrity and air pressure capability to withstand both the changing load and corresponding heat generation without compromising performance.
David Graden, operational market manager, agriculture, Michelin North America Inc.: The big idea behind IF/VF technology was to enable tires to carry more weight than standard radial tires without really changing the size of the air chamber. This technology also gives equipment manufacturers a larger range of tires to carry heavier machines or increased hopper and tank sizes on harvesters and sprayers.
IF tires widely hit the market first. IF tires can carry up to 20% more load than standard tires at the same air pressure or they can operate at 20% less air pressure and carry the same load as a standard tire. VF tires hit the market immediately after and will carry up to 40% more load than standard tires at the same air pressure or they can operate at 40% less air pressure and carry the same load as a standard tire.
Both IF and VF technology allow a tire to operate at its fullest capacity, meaning the footprint of an IF/VF tire is maximized both wide and long. It allows the full width of each lug to contact the ground, in addition to putting more lugs on the ground, due to a longer footprint. These features, combined, will produce maximum traction and floatation for any field application.
To take it one step further, IF/VF technology has also enabled us to add the CFO index to harvester and sprayer tires. This technology takes into account the short amount of time a tire is under maximum pressure due to a full hopper or sprayer tank. Since this weight diminishes over time, we have created an inflation pressure table which allows the user to be more precise with air pressures and truly set the lowest air pressures to carry the maximum weights, in field. As mentioned earlier, add a CTIS to this technology and you can really maximize your machine’s efficiency and productivity.
Blaine Cox, national product manager — agriculture, golf and turf, Yokohama Off-Highway Tires America Inc: IF and VF tires — and their ability to carry even higher loads under the CFO designation — are probably the most exciting technology in the ag tire business today, with the greatest potential to help improve productivity on the farm.
That’s because IF and VF Tires can help farmers reduce compaction force on their soils by 20% to 40% or carry higher loads than conventional radials without increasing compaction.
IF and VF tires are the products of amazing engineering, cutting-edge materials and meticulous construction that allow us to construct extremely flexible, extremely tough IF and VF sidewalls and snug beads. The result is that those tires can carry extremely heavy loads at low inflation pressure without the strain and heat buildup that would occur with conventional radials or bias-ply tires at those pressures.
With IF and VF, you can also choose which benefit you want to take advantage of — higher load at the same pressure or the same load at lower inflation. The extra flexibility in the sidewalls and outstanding performance of the casings of IF and VF tires create a longer, larger footprint, which spreads load to reduce soil compaction, puts more lugs on the ground for greater traction and improves fuel efficiency.
On top of that remarkable capacity, there’s a cyclic field operation load bonus. Look for “CFO” on the sidewall like this: VF420/95R50 CFO. During harvest, loads increase and decrease as grain moves onto and off the combine or grain cart. On harvesters and grain carts, CFO changes the game. At speeds of 10 mph or less, CFO ratings allow an increase in the permitted maximum load on IF tires by as much as 55% and VF tires as much as 35.5%. At 20 mph, an IF tire can carry 30% higher load due to its CFO rating, while a VF tire in cyclic field operations can carry 13.5% more.
There are some very important restrictions to CFO use. First, the machine must operate in the field at or below the designated speed — usually 10 mph. It must also cycle through the load. It can only carry the maximum CFO load no more than one mile before unloading begins. On the road, the machine must be empty or operate within normal load/speed parameters.
