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Mechanics Corner: Heavy loads require proper tire selection

Published on 24 May 2016
Spring is a tire checkup

Dairy producers have a lot riding on the performance and durability of their equipment tires, especially as equipment size and weight have dramatically increased in recent years.

Selecting the right tires to meet capacity needs is key to reducing the risk of tire damage or even tire failure.

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One challenge arises when a dairy producer purchases a new 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. This 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 for long periods of time. The first sign of trouble may be a wrinkle or bend in the tire behind the lug, followed by the torqueing or folding of the tire casing. Tires can also experience excessive flexing for their design and cord separation in the sidewall.

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Besides tire damage, excessive weight also results in another serious problem – soil compaction – caused by today’s high-powered tractors and heavy harvesting equipment. Excessive tire pressure against the soil can damage plant roots, reducing crop yield potential. Heavy grain carts and manure spreaders that follow combine tracks can further compress ruts across the field.

Avoid overloading

Dairy producers can consider several options to avoid overloading. One solution may be to determine 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. This decrease in pressure required to carry the load provides a larger footprint to spread the weight of the machine over a larger contact patch.

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

Determine proper weight

Producers 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.

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Using only the owner’s manual as a guide means you are at risk for overloading and the resulting tire damage that can be caused. 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.

Maintain proper tire pressure

Similarly, determining the right air pressure based on your owner’s manual could result in underinflated tires. That can lead to irreversible damage to tire casings and even tire failure, excessive wear during road travel due to a smaller contact area and difficulty in maneuvering at field speeds.

Conversely, overinflation may cause excessive soil compaction as well as result in a less comfortable ride due to bouncing and vibration. Too much air pressure can also increase the amount of tire slippage, causing excess fuel consumption and excessive wear on both tires and the machine.

An owner’s manual only shows the weights for a static tractor in normal operating conditions. This is rarely the way farmers take their 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 to accommodate for terrain changes and load shift.

Select the best tire for your application

When buying new or replacement tires, start by looking at the same tire size you currently have on the machine. Then explore what options are available in that size to meet the specific conditions on your farm. For example, this might entail specific load-carrying requirements or environmental issues, such as the need for stubble resistance.

For today’s bigger, more powerful equipment, larger tires are needed to efficiently transfer power to the ground. Make sure you have enough rubber, since undersized tires can result in poor traction, reduced fuel economy and an increased tendency for compaction.

Consider value, not just cost. A new or replacement tire that offers the best value is not necessarily the one with the lowest price. Select a tire that is best for your application needs while also offering good performance and durability. That’s the best measure of the overall cost of ownership and return on your tire investment.

Spring is an optimal time for a tire checkup. Ensure that you have the right tires for your different applications, know their weight capacities and inflate tires to the correct pressure. These steps will help extend the life of your tires, reduce the risk of overloading, minimize soil compaction and maximize performance in the field.  PD

PHOTO: Spring is an optimal time for a tire checkup. Ensure that you have the right tires for your different applications, know their weight capacities and inflate tires to the correct pressure. Photo by ThinkStock.

James Crouch
  • James Crouch

  • Farm Segment Marketing Manager
  • Michelin Ag Tires
  • Email James Crouch

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