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Mechanics Corner: Heavy front loads require proper tire selection

Contributed by James Crouch Published on 26 February 2016

Because of the heavy loads forage growers handle, selecting the right tires for equipment is especially important. Insufficient tire capacity can result in tire damage or even tire failure.

The problem can typically arise if a farmer purchases a tractor and then adds a front-end loader without taking into consideration the additional weight put on the front axle. The result is overloading as the combined weight of the tractor and front load shifts forward.

The tire risk is particularly high for lower-horsepower tractors that use singles rather than duals.

For example, a 245-hp tractor can place 12,000 pounds of weight on the front axle. Adding a front-end loader with a bale of hay can easily increase that weight by 20 to 40 percent as the center of gravity is shifted.

The problem can be intensified by certain operational factors that may not be considered. For example, hitting the brakes suddenly or going downhill can shift even more weight forward.

Even the highest-quality tire can fail if its maximum weight capacity is exceeded. The first sign of trouble may be a wrinkle or bend in the tire behind the lug, followed by torqueing or folding of the tire casing. Tires can also experience excessive flexing for their design and cord separation in the sidewall.

Besides tire damage, excessive weight also causes another serious problem: soil compaction. Excessive tire pressure against the soil can damage plant roots, reducing crop yield potential. Heavy equipment such as grain carts and manure spreaders that follow combine tracks can further compress ruts across the field.

Taking a load off

Forage growers can consider several options to avoid overloading. One solution may be to see if there is a higher load index available in the same tire size. Switching from singles to duals, depending on the equipment, can also help spread the weight of the load.

Another remedy is to operate with lower tire pressure, creating a larger footprint to help spread the weight of equipment, thereby reducing the risk of tire damage and soil compaction.

Compared to conventional ag radial tires, increased flexion (IF) and very high flexion (VF) tires can carry the same load at 20 percent or 40 percent lower air pressure, respectively, or a 20 percent or 40 percent heavier load at the same pressure.

Currently, there is a gradual conversion from conventional to IF or VF radial farm tires. Equipment manufacturers are starting to see the benefits of tires designed to operate at lower pressure as more farmers request IF/VF tire models. A similar trend is being experienced in the tire replacement market.

Other considerations to protect your tires 

Determining proper weight
Farmers often look to their owner’s manual to determine proper weight loads. However, these guidelines do not take into account added weight features, such as a front-end loader. As noted previously, carrying one or two heavy bales can put significantly increased weight on the front axle.

Using only the owner’s manual as a guide means you are at risk for overloading and the resulting tire damage it can cause. Instead, ask your manufacturer’s rep to bring a set of scales to the farm – or use those at your local grain elevator – to get a true weight of the axle load based on the weight you expect to carry. Then, check the tire manufacturer’s website for the correct tire requirements.

Proper tire pressure
Similarly, determining the right air pressure based on your owner’s manual could result in underinflated tires. An owner’s manual only shows the weights for a static tractor in normal operating conditions. This is rarely the way farmers take equipment into the field. Hitting a bump in the field or sudden braking can cause temporary overloading on the tires.

To compensate, it is recommended that you adjust your air pressures to account for these conditions. To do this, you must inflate the tire enough to make sure it is never overloaded. When calculating the air pressure needed to carry the load on the tractor, you should increase the amount of load measured by 12 percent for a dual configuration and by 18 percent for triples.

Reversing tires
Running the front tires backward is a common practice for certain applications, such as bucket work with a front-end loader, when more traction is desired. Farmers often ask if this affects the life of the tire. The answer is no – but there is another risk.

Because ag tires have a directional tread, reversing the tire and forgetting to change it back for row-crop use could result in significant corn stubble damage during harvest. The tread is designed to deflect stubble away from the center of the tire.

Operating with the tire in reverse does exactly the opposite, pushing the stubble to the center of the tire, which dramatically increases stubble damage risk.

Ensuring that you select the right tires for your application and inflating them to the correct pressure will help extend the life of your tires, reduce the risk of soil compaction and maximize performance in the field.  FG

James Crouch is farm segment marketing manager for Michelin Ag Tires.

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