Preload Instead of Setting Endplay Gaining Favor

Judy of Coppercoin says he has experienced far less wheel seal failures since using the Temper technology to adjust the wheel bearings to light preload. “If I have six technicians in the shop, they can all be trained to adjust the bearings to the same preload setting. It takes the guesswork out.”

Gerry Greca, a Federal-Mogul technical specialist, says: “All components within the wheel end system benefit under controlled preload setting. To achieve controlled preload, one must follow a procedure that ensures both accurate and repeatable method. This procedure must result in an approved load range.

“Attention to accuracy, repeatability and following the proper load range specifications are key. SAE Standard J2535, Setting Preload in Heavy Duty Wheel Bearings, was created as a recommendation for an optimized load range.”

“The seal has two basic functions: to keep lubricant in and contaminates out,” continues Greca. “Preload provides truer motion between the hub and spindle. Better alignment gives the seal design engineer luxury in minimizing clearance and interference, resulting in better followability and less heat generation.”

TIRE WEAR

Uneven tire wear plagues many fleets and owner/operators. Even with proper alignment, tire inflation and driving conditions, tires can wear prematurely and unevenly because of loose bearing settings.

Frank Evans, the owner of F & R Industries, saw his tire wear issues disappear after setting every wheel end on his tractor and trailer fleet to light preload using the latest preloading system.

“In the sand and gravel business, we are always running high weight loads and maneuvering in tight positions,” he says. “Since converting our fleet to preload bearing settings, wheel ends are no longer an issue. Our tire wear problems, which were often severe, are totally gone.

“It doesn’t make sense to set a wheel end to endplay,” continues Evans. “Preload tools now available make everybody in the shop an expert at setting bearings because they are measuring how much preload is applied in the wheel end. It takes away the guesswork.”

Guy J. Walenga, director of engineering of commercial products and technology for tire manufacturer Bridgestone Americas, confirms the results experienced at F & R Industries.

“A loose bearing at the axle end creates artificial negative camber and is a reason for premature wear on the inside shoulders of the tires,” he says. “As tires become more and more finely engineered, they are more sensitive to movement in other parts on the vehicle.”

VEHICLE COMPONENTS

Meritor, a leading global supplier of drivetrain, mobility, braking and aftermarket solutions for commercial vehicle and industrial markets, recognizes the importance of wheel end bearing adjustment to the performance of vehicle components well beyond the bearings themselves.

With a focus on the experiences of the industry with single wide tires, its Understanding the Impact of Wide Base Single Tires whitepaper, dated November 2011, suggests that the wheel end loses 10 percent of its life for every 0.001” of endplay. So, a wheel end set at 0.004” endplay, still within TMC RP 618’s range of 0.001” to 0.005” endplay, would last 40 percent less than a bearing set to the zero point (no endplay or preload).

When preloading tools are used, the results are even better for increasing tire and wheel life.

COST SAVINGS

Properly adjusting wheel end bearings to light preload can save hundreds and even thousands of dollars on every wheel when compared to wheel ends that are in endplay.

A single wheel end can be set to light preload at an incremental cost of around $20. This investment is recouped very quickly with cost savings when tires wear evenly, seals remain intact, fuel efficiencies occur, brake systems operate correctly and bearings gain operating life.

Fleet maintenance shops and truck service centers aren’t the only ones on the path to adopting preload settings for wheel end bearings.

Axles for original equipment tractors, trailers and coaches are “dressed” with wheel ends at one of several points as they are made. Manufacturers of axles, suspensions, chassis and final equipment all have production areas to assemble wheel ends.