When considering axles that boost your efficiency, you’d likely want to extend those efficiency gains out to your wheel end through the spec’ing of high-efficiency bearings for that extra fraction of fuel efficiency gain. While a fraction of a percentage might not seem like a lot for one truck, spread it out across your entire fleet and the savings can build up fast.

“Bearings are often hidden inside other equipment like axles and transmissions, but can deliver significant fuel efficiency benefits if properly designed and specified,” said Matt Zwick, application engineer specialist for mobile industries with The Timken Co. “If used at both axle center and wheel end applications, high efficiency bearings can save as much as 1.6% at the vehicle level. At 100,000 miles per year at 6 MPG, that equates to 195 gallons of fuel per year.”

Of course, those figures can be impacted by a multitude of factors including vehicle design, functionality, duty cycle, application, performance, and other factors that can influence the effectiveness, feasibility and cost.

“Utilizing high-efficiency bearings reduces friction losses, thereby contributing to the overall fuel economy,” noted Divjot Singh, applications engineer with NTN-Bower. “Calculating exact savings will vary by the application and will be different for various fleets.”

What constitutes a high-efficiency bearing? That can depend on the manufacturer. For example, Singh says NTN-Bower crowns the bearing’s rolling surfaces to better distribute the load and reduce edge stress, thereby increasing efficiency. Crowning is standard across all NTN-Bower products.

Click here to read more wheel bearing maintenance tips.

“Other ways to increase efficiency include improving the surface finish of the rolling surfaces, and incorporating sphering [on the rollers], which reduces friction,” Singh said.

“Higher quality, cleaner steels, enhanced internal profiles, smoother finishes and downsized macro-geometry all contribute to reduced friction and improved fuel efficiency,” Timken’s Zwick answered. “Continuous improvements in bearing-making technology in recent years make this possible.”

Keeping bearings free of contaminants is key to keeping them rolling efficiently. In many shops, wheel maintenance is usually the arena of the least experienced technician on the fleet’s payroll. Fleets would be wise to ensure that the technicians on wheel-end duty are well versed in the proper cleaning and lubrication procedures to maintain specialized bearings. That means following the TMC recommended wheel bearing adjustment practice (RP 618A) in order to prevent bearing failure. TMC recommends achieving a verifiable bearing endplay of 0.001 to 0.005 in. This should be verified by use of a dial indicator. Additionally, NTN-Bower’s Singh said that wheel separation is a serious problem.

In terms of proper maintenance practices, Singh recommended the following:

• Always use proper tools to install races and never pound on the race—it may cause damage. If proper tools are not available, an old race may be used as a tool to install the new race.
• Keep the bearings covered (or in the boxes) until the truck is ready to be worked on. Otherwise bearings may become contaminated with dirt or debris from the surroundings, which will dent the rolling surfaces, leading to noise and reduction in bearing life.
• Always replace matched bearing sets rather than individual cups and cones.

Both NTN-Bower and Timken offer bearing and wheel end training.