s a f e t y   &  o p e r a t i o n s

Service Savers

Unitized hubs can make the wheel-end a no-service assembly for the life of the truck.

STEVE STURGESS
SENIOR EDITOR

      Wheel hubs are simple: just a couple of bearings, a seal and a retaining system that provides adjustment. But depending on the skill of the technician assigned to wheel-end service, wheel-ends could be a high-maintenance item responsible for unscheduled downtime, contaminated brakes or even lost wheels. Conversely, with the right technicians, wheel-ends could be trouble free.
      Recent advances in hubs, seals and bearing packages are taking the need for skilled technicians out of the equation and keeping trucks out of the shop. Lubricant technology and the internal design of the hub are putting lubes in better contact with bearings, guaranteeing a long life and minimum power consumption.
      Advances in material specifications for hubs and drums are resulting in lower weight at the wheel-ends at reduced cost, enhancing vehicle productivity and resale value.

Fit And Forget
      Around 15 years ago, it was not at all unusual to see the tell-tale oil streaks on truck or trailer wheels that showed oil leaking past a seal. Most often it signified an incorrectly set bearing end play or an early seal failure most likely caused by an improper installation either at the truck manufacturer if it were a new vehicle, or in the service shop in the case of an older one.
      Newer unitized hubs are factory pre-assembled with accurately stacked bearings and spacers and have produced wheel-end systems that eliminate those installation issues.
      Because the bearings are given the correct pre-load — virtually impossible to guarantee in the shop with conventional dual-nut spindles — they retain their adjustment over the maximum possible life. This means no service and no opportunity to introduce contamination into the bearing cavity.
      Since the bearings in a system hub are in a pre-loaded condition, the seal has the optimum running condition too, enhancing the life of a part that has also been considerably upgraded in recent years. Most are warranted at least for the first life of the truck.
      ArvinMeritor brought the unitized hub to the front axle something like five years ago with its introduction on the EastSteer FF981 axle. According to Tim Farney, director of marketing for the Meritor axle division, this enabled the company to gain experience with low- and no-service hubs.
      ArvinMeritor also explored the weight savings of aluminum hubs with the UWE-90, introduced several years ago. This SKF bearing-and-seal technology drive-axle hub is pre-assembled and permanently lubricated and can save 115 pounds over ductile iron on a drive tandem.
      Now ArvinMeritor is rolling out a series of extended-life trailer hubs providing lower cost options to the premium TB introduced four years ago. This hub is made entirely from bearing steel so is at the premium end, but comes with a premium warranty today of 7 years, 700,000 miles. Complementing this trailer hub are new products like the lower-cost Triad that requires annual inspection but no maintenance for a three-year, 300,000-mile warranty and the TL and the TA, rolling out this year, which come with half-million-mile, five-year warranties. These warranty periods show the confidence that ArvinMeritor has in the unitized hubs that can easily go 800,000 to a million miles without any kind of service, says Meritor trailer products marketing manager Varun Rao.
      These later introductions feature ductile iron hubs which, through CAD designs are getting down to comparable weights to aluminum hubs.
      Dana captured the low-maintenance name for itself when it registered its low-maintenance trailer axle the LMS. Among other features, these axles featured wheel-ends with pre-loaded high-tolerance bearings accurately located by a spacer and featuring the Outrunner oilseals. These hubs are available in iron or aluminum.
      Gunite last year introduced its low-maintenance hubs, initially under the LMS label since they incorporated Dana's LMS technology. This hub combines factory assembly and bearing preload with its standard Ductilelite ductile-iron hubs. Now re-named High Performance, these hubs are also available with the Stemco Advantage system.
      For weight savings, Hayes Lemmerz has introduced the CentruLite lightweight cast aluminum trailer-axle hub. It is available for TN axles with a cast aluminum P axle hub due for release later this year.

One-Stop Shop
      Hendrickson, which is aggressively expanding its one-stop-shop philosophy, has added unitized hubs for its Intraax and Vantraax trailer axles and its innovative AirTek air-suspended front axle.
      Launched under the HUS (Hendrickson Unitized System) tag, these hubs feature SKF LUNAR technology similar to the Meritor TB hub and offer the same 7-year, 700,000-mile warranty on the trailer axles.
      On the steer axle, Hendrickson combines its lightweight fabricated-beam axle with ConMet's unitized aluminum hub. This saves even more than the 90 pounds that the AirTek axle/spring saves while gaining a no-service unitized wheel-end. Hendrickson claims the ConMet hub marks the first time a unitized aluminum hub has been made available for front axle usage in North America.

Other Answers
      More conventionally, Hendrickson has also introduced Value Package, an extended-service trailer option that matches a ductile iron hub assembly with Stemco's Advantage System. It offers more competitive pricing and a single-source for service warranties, says Hendrickson. The Advantage System offers a five-year limited warranty, and field serviceable components.
      Webb's aluminum 4023 hubs are now available for the TN axle, with other aluminum hubs to be available soon all offered with the Stemco Advantage System as an option. These hubs can be combined with the recently announced Platinum Series brake drums that are manufactured from a patent-pending material that is lightweight, low wear and has high heat transfer characteristics for a low-maintenance hub/drum package, says the company.
      Timken is aggressively promoting its Wheel Boss bearing system which incorporates a unique locking adjusting nut that it says guarantees accurate wheel-bearing adjustment in conventional hubs. Included in the system is a seal and a non-vented hubcap and Timken includes a seal installation tool to guarantee accurate installation of the seal.
      Chicago Rawhide's Scottseal Plus XL is guaranteed for 3 years, 300,000 miles. The four-lip seal is the premier offering in the Scottseal line and is claimed easy to install without the need for special tools, eliminating the main source of seal leakage problems, says the company.