Rock Products

APR 2017

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www.rockproducts.com ROCK products • April 2017 • 31 Because bias and radial tires are intended to be used differ- ently, 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 perfor- mance when used in the correct application. Constructed of multiple cross-plies, they are built primarily with nylon from its casing to the sidewall. 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 applica- tions 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 catego- ries 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 unim- proved 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 selec- tion 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 trans- porting 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 fre- quently 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. In applications where a loader does a fair amount of tramming, radial would be the best fit.

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