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How Bias Can Provide Cost and Performance Benefits.
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Beyond the decision of bias versus radial, tread depth can also have an impact on cost per hour.

As construction equipment has grown in the last couple decades – in size, power, weight and speed – so too has the need for off-the-road tires that can keep up with the increased demand. As such, a tire market that was comprised of 100-percent bias designs only a couple decades ago has now moved primarily to radial for larger earthmoving equipment.

While radial technology outperforms bias in many instances (justifying the increased cost), bias tires, when used in the proper application, can provide significant cost savings and performance benefits over radial – proving the latest isn’t always the greatest.

This is particularly true in a quarry setting, where a bias may be a better fit for one loader and radial may be a better fit for another loader on the same site. It all comes down to how the tire is being used.

“I see a lot of customers purchasing radial, often simply because of the assumption that it’s going to be a better tire,” said Johni Francis, OTR global product manager for Titan International. “However, it’s not whether radial is better than bias, but what works best for their specific application. They aren’t going to see any difference in benefits from a radial over a bias in certain applications. In fact, the radial may not perform as well as the bias.”

Because bias and radial tires are intended to be used differently, they are produced differently. Knowing the differences in the way they are designed can help an equipment owner determine the right tire for the job – and potentially save money in the long run – especially considering bias tires offer roughly a 30 percent cost savings over radials.

Bias tires offer many characteristics for superior performance when used in the correct application. Constructed of multiple cross-plies, they are built primarily with nylon from its casing to the sidewall.

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In applications where a loader does a fair amount of tramming, radial would be the best fit.

Several layers provide the benefit of increased puncture resistance in the sidewall, and it’s often easier to repair the nylon plies of a bias as compared to the steel belts of a radial. This bias design also results in less sidewall flexibility and greater stability, which can result in better breakout force on a loader, potentially less bucket spillage and increased operator comfort.

Radial tires are constructed with steel belts to protect the tread area and generate less heat for a longer life in haulage applications. The design also offers a greater weight load capacity at lower inflation pressures – ideal for applications that require heavier loads at faster speeds and longer distances.

So what determines which design is the most applicable for a job? Speed and distance are two major factors.

Intended Uses

The Tire and Rim Association (TRA) has several categories of applications that apply with speed and distance requirements:

  • The E category (earthmover) is designed for haulage and transport of materials on unimproved surfaces at up to 40 mph and up to 2.5 miles at a time.
  • G (graders) are designed for grading material over unimproved surfaces at speeds up to 25 mph and for unlimited distances.
  • The L category (loader) is designed for use on loaders and dozers that do not exceed 5 mph and distances of 250 ft. each way.

While these are seemingly clear-cut parameters, design selection is dependent on how whether the machine is being used to its full weight and speed capacity or not.

“One could conclude that since radials are better for longer distances, they’re perfect for graders. However, that’s not always the case. Just because the category has the capability of going up to a certain speed doesn’t necessarily mean it’s going to,” said Francis.

For example, on average, the working speed of a grader is typically between 5 to 6 mph. If tramming with the blade up, it typically runs around 16 mph. So, even though it’s capable of traveling up to speeds of 25 mph, it rarely does.

“If you typically work on site prep jobs where you’re transporting your grader on a trailer to the jobsite, grading at the jobsite and then transporting the grader on a trailer to the next job, chances are you very rarely run the grader beyond the 5 to 6 mph for long distances,” Francis said. “This is an instance where bias may offer cost savings. However, if you’re doing road maintenance in a municipality where you’re frequently traveling at higher speeds and greater distances between roads, radial is going to be a better choice.”

The same principals would apply in a quarry setting. If your loader is confined to a small footprint area, such as loading a stationary crusher, and isn’t traveling too far, bias may be the best fit. In load and carry operations, if you’re frequently tramming between two load-out points, radial would be ideal.

Another example of how radials are often used when they’re not necessary is in underground mine settings – which aren’t your typical haulage application.

With the narrow corridors, most underground loaders rarely run beyond 5 mph. Additionally, there’s an increased risk to the sidewall when running in such close quarters. With the extra sidewall protection of bias, you may actually get longer life compared to a radial – not to mention the cost savings.

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When confined to a small footprint area, bias is often a better fit because of the short distances traveled.

While speed and distance are key factors, so too is load. It’s important for fleet owners to understand how load impacts a tire’s speed and distance capabilities – as they differ between bias and radial.

“The higher the PSI, the higher the load rating. If you bump up the PSI, but do not bump up the load, you can utilize that tire a little bit harder. It allows you to travel faster without generating so much heat. And it works vice versa – you can carry more loads but can’t travel as fast,” said Francis.

Determining the exact average speeds, distances and loads a machine is functioning at isn’t always a straightforward process. Thus, you may not immediately know whether switching back to bias would make sense. However, there are tools and technologies available to help make a more informed decision.

Factors for Making the Switch

There are important key factors to know if switching back from radial to bias. First, conducting a VBOX study may be necessary to see if you’re exceeding the speed and distance requirements for bias. A VBOX study documents average speeds, stopping and starting times, tonnage moved/day, cycles/day, and loads on an average basis.

“The data captured from a VBOX study can be crucial to see if they’re under the requirements for radials – and whether or not bias would work,” Francis said. “Unless the situation is very clear-cut, I often recommend a VBOX study prior to the customer switching from radial to bias.”

Some of the situations above usually require research and can be questionable, but there are other applications where bias is an obvious choice. In situations with high risk of punctures, and where speed and distance aren’t a huge factor, bias is often the most practical design for that application.

Control your Bottom Line

Despite the industry’s rising demand for radials, they’re not always the best fit. Bias will remain the key to cost savings and increased performance in a variety of proper applications. To find out if bias is right for you, consult with your local tire representative.

Information courtesy of Rachel Lium, Two Rivers Marketing.