With safety and maintenance issues of primary concern to fleets, it's not surprising that use of hub-piloted mounts continues to grow steadily. Accuride is seeing growth of about 5-10% a year. Currently, about 68% of the steel wheels it sells to OEMs are hub mounts, although the number drops to about 63% when the aftermarket is included. Although the trend is still upward, the numbers are slightly lower in the aluminum end of the market.

Hub-piloted wheels are generally less complicated to maintain, with fewer parts than other mounting systems, according to Ross Hill, director of engineering for Hayes Lemmerz International. However, Accuride's Chuck Scarton, manager, product commercialization, says the industry recommends that wheels be re-torqued at periodic intervals, and especially after the first 50 or 100 miles following the installation of new tires and wheels. Another advantage of hub-mounted disc wheels is their superior clamping force.

Accuride makes steel and aluminum disc wheels, including both hub- and stud-piloted models, as well as their trademark Duplex wide-base wheel.

In its efforts to serve a market that lies somewhere between steel and aluminum, Accuride is introducing a less expensive version of its ProSteel model this fall. The new powder top-coated, styled steel wheel combines the look of aluminum with the strength of steel.

According to Accuride, the durability of this improved coating system should significantly reduce refurbishing costs. After being pretreated with zinc phosphate, the steel is given an electrodeposited primer and a sparkle metallic powder topcoat. By offering greater resistance to chips and corrosion, the wheels are expected to maintain their aluminum-like appearance and last twice as long as standard coated steel wheels, provided that proper maintenance practices are followed.

Alcoa offers both hub- and stud-piloted aluminum disc wheels, including a line of "New Generation" hub-piloted forged aluminum wheels that offer low weight and high strength. The 22.5 x 8.25 model, for example, weighs only 49 lb. and is load-rated to 7,300 lb. Alcoa says that using New Generation wheels, rather than stud-piloted steel wheels, on an 18-wheel vehicle can result in a weight savings of 688 lb.

Another advantage to these wheels is their low-maintenance requirements. Since the New Generation wheels are designed to resist corrosion, Alcoa says fleets don't need to worry about sandblasting, priming, or painting them. This means less downtime and no money spent on painting, both of which can help offset the higher cost of aluminum wheels. In addition, the size of the hand holes have been increased by half an inch, making mounting and demounting easier.

Alcoa research shows that aluminum wheels increase the resale value of heavy-duty trucks, especially when they are positioned on front axles. In general, aluminum wheels depreciate at a rate about half that of the truck.

Hayes Wheels and Lemmerz Holding GmbH have merged to become Hayes Lemmerz International. At present, Hayes Lemmerz makes steel disc wheels for Class 3-8 trucks (hub-piloted and stud-piloted). There are some indications, however, that aluminum disc wheels may play a role in the company's future.

Hayes Lemmerz has added new stud-piloted and hub-piloted tubeless wheels to its product line this year, as well as a wheel fastening system for heavy-duty trucks and trailers.

The tubeless 17.5-in. stud-piloted wheel has two hand holes and is available with either six or ten bolt holes. The 6-hole model weighs 63 lb. and the 10-hole model 62 lb. Maximum load rating is 5,070 lb.

Two 19.5-in. tubeless hub-piloted wheels have also been added to the Hayes Lemmerz inventory. The 10-hole model weighs 63 lb., and features five hand holes and a maximum load rating of 6,700 lb. An 8-hole version weighs 61 lb., has four hand holes, and a maximum load rating of 5,000 lb.

Developed for hub-piloted systems, the company's Hayes-L-Nut fastener is designed to better withstand the wheel loosening (torque loss) associated with contaminants, paint loss, and the normal "seating-in" process. This torque loss can then lead to wheel breakage and wheel-off conditions.

The new wheel fastening system is made up of a series of belleville washers integrated into the nut, making it analogous to "an unloaded spring before torquing." According to Hayes Lemmerz, "the washers act like springs to reduce the effects of torque loss from the normal seating-in process when paint, dirt, and metal-surface irregularities wear away." The spring-like washers continue to exert pressure between the Hayes-L-Nut and the wheel mounting surfaces.

Since proper installation and maintenance play such a crucial role in truck-wheel safety, technicians should keep the following in mind when installing disc wheels:

* Check all parts for damage and ensure that the studs, nuts, pilots, and mounting faces of the hubs, drums, and wheels are free of dirt and grease.

* Remove excessive paint from the wheels.

* Make sure the correct fasteners are used, and never mix fasteners between systems.

The "User's Guide To Wheels & Rims," an illustrated guide to all these potential problems, is available from The Maintenance Council of the American Trucking Assns. For information, call 1-800-ATA LINE.