By David Walters, Senior Technical Service Specialist, Alcoa Wheel Products International
Ball seat and hub piloted aluminum wheels offer advantages such as cool, true running for longer tire and brake life; weight saving for more fuel efficiency or payload capacity; and paint-free good looks that enhance professional image and driver pride. For such sophisticated equipment, today’s disc wheel systems remain relatively simple to maintain. The time you spend on your wheels can pay off with improved safety and performance.
Make sure to follow all recommended safe work practices and regulations, such as using an approved safety cage when inflating a wheel/tire assembly. Follow proper installation procedures.
Ball seat systems
The ball seat nut has a precision-machined spherical surface that seats into the wheel. Also known as the double cap nut system, the ball seat system uses inner and outer cap nuts with each stud for dual wheel positions. A single nut is used for single wheel positions. For vehicles with standard length studs, proper stud standout for single wheels is 1.6-inch (1-5/8-inch) minimum; for dualed, 1.31 to 1.44-inch (1-5/16″ to 1-7/16″). Measure stud standout from the axle end mounting surface (the surface the wheel sets against) to the end of the stud.
Some vehicles use studs longer than standard. Lengths up to 1.88-inch (1-7/8-inch) are acceptable, but be sure to use proper inner cap nuts with these longer studs. Ask your wheel distributor for the recommended inner cap nuts.
When you change types of brake drums, check for stud standout in excess of 1.88″ (1-7/8″). Excessive stud standout may cause the inner cap nut to bottom out on the longer stud, preventing proper wheel seating.
If you lubricate the stud threads on your stud located system, torque between 350 to 400 foot-pounds. If you do not lubricate the threads, torque between 450 to 500 foot-pounds.
Sometimes an aluminum wheel is dualed with a steel wheels. When dualing aluminum wheels with steel, follow the steel wheel manufacturer’s recommendations regarding proper torque and use of thread lubricants to mount the wheel. When you use a steel inner wheel with an aluminum outer, use extreme care to properly seat the steel inner wheel to the hub or drum before mounting the outer aluminum wheel. Use an inner cap nut specially designed for fixing the steel inner wheel and providing adequate external thread length to secure the outer aluminum wheel.
Recheck torque after 50 to 100 miles of operation, and at frequent intervals from then on:
Loosen outer cap nuts on every other stud to check the torque on inner cap nuts.
Retorque the inner cap nuts
Then retorque the outer cap nuts
Then repeat the procedure on the remaining studs.
Hub piloted systems
The hub piloted system centers the wheel on the hub pilots, not the studs. Unlike the double cap nut system, the hub piloted system uses only one nut per stud. The nut consists of a body permanently attached to a flat washer. The body rotates against the washer, not against the wheel. The result is less nut-to-wheel abrasion, less galling and up to three times more clamping force than traditional ball seat systems.
Lubrication. A dry pilot is susceptible to corrosion build-up between the wheel and hub bore, making wheel removal difficult. Ideally, your manufacturer will have lubricated the pilots before shipping your new vehicles from the factory. Field reports indicate vehicles are sometimes delivered dry, so take off the wheels and check the hub pads for yourself. If they are dry, lubricate the hub pilot pad or hub bore with a non-water based lubricant, such as Freylube, and remount the wheels. Do not lubricate the face of the wheel, hub or brake drum.
To help combat corrosion before it gets started, Alcoa added a new feature to the hub piloted wheel design: a groove recessed into the hub center bore. The groove reduces by nearly 50% the contact area where corrosion can build up. Less corrosion results in easier wheel removal.
Although new wheel hardware does not need lubrication, a few well-placed drops of oil on hardware already in use will help minimize corrosion between mating surfaces. Before installing two-piece flange nuts, lightly lubricate the stud threads and the contact surfaces between the cap nut and the washer with an SAE 30W oil.
Measure up. While an aluminum wheel weighs less a steel wheel, the aluminum wheel is thicker. Hubs designed for steel hub piloted wheels may not have enough pilot length to locate dualed aluminum wheels. This is an important issue, particularly if you’re converting from steel to aluminum duals. Measure the hub pilot to make sure you have a minimum of 1.06 inches or 27mm for dualed aluminum wheels.
Studs must be of sufficient length as well. On heavy duty trucks, proper stud standout for single wheels is 2-inch (50.8mm) minimum; for dualed, 2.81-inch (71.4mm) minimum. Measure stud standout from the axle end mounting surface to the end of the stud.
Snug nuts. Nuts should be “snugged up” before tightening. This allows the wheel to center itself before it is fully torqued. Turn the hub so one of the pilot pads is at the 12 o’clock position. Then position the wheel on the pilot pads. In a dual assembly, the outer wheel often cocks at an angle. Many problems with dual wheels can be prevented by making sure the top nut is tightened first to seat the wheels. The pressure from each nut, tightened in the right sequence, helps to seat the wheel straight and even against the hub. Follow the recommended sequence in your wheel service manual to hand-tighten the flange nuts.
Torque. After hand-tightening, use a torque wrench, or a correctly calibrated air wrench, to tighten the nuts to the recommended torque. If you use an air wrench, keep it adjusted to apply the right amount of torque. Again, tighten in the recommended sequence to ensure proper seating.
A 33mm or 1-1/2″ hex head flange nut should be torqued to 450 to 500 foot-pounds – the same torque recommended for ball seat wheels. Confirm you have proper torque by checking a tightened cap nut with a torque wrench. Recheck the torque after 50 to 100 miles of operation. After each wheel mounting, check cap nut torque with a torque wrench.
Like any hard-working component on your truck, hub piloted and ball seat wheels need to be inspected regularly to assure proper performance. During tire changes, thoroughly examine the entire wheel. Pay particular attention to the rim contour and rim surfaces.
Grime can hide damage and interfere with seating. Clean the wheel face with mild detergent and the tire bead seat with a wire brush. Inspect the wheel for damage such as:
Stud hole cracks, usually caused by improper torquing, excessive load or insufficient mounting flange support by the hub or brake drum
Cracks from stud hole to stud hole, caused by undersized diameter of wheel support surface or insufficient torque
Wallowed out or elongated stud holes, caused by loose running wheels
Cracks around the valve stem hole, which can result in air loss
Never try to repair a cracked wheel. Remove cracked wheels from service.
Check the rim flange for irregular wear, caused by the chafer of the tire. Check the rim flange for sharp edges that can cut the tire. Follow recommended procedures from Alcoa to maintain proper flanges.
Measure the degree of wear with a rim flange gauge, available from Alcoa Wheel Products International. Place the flange gauge on the rim flange. If you see daylight between the gauge and the wheel bead area, the rim is acceptable. No daylight means the rim is too worn to keep in service. Remove excessively worn wheels from service.
A corroded wheel can “freeze” to the hub, a headache to remove. Corrosion can compromise a wheel’s appearance, and, in extreme cases, its strength. Remove any severely corroded wheel from service.
Steel wheels have to be protected with paint; corrosion-resistant aluminum wheels do not. However, certain environments can corrode both steel and aluminum. These include salt, chloride compounds used for snow removal, highly alkaline materials and moisture. To ward off corrosion, use only non-water based lubricants. Make sure the air you use to fill a tubeless tire, and the tire itself, is dry.
A service manual from your wheel manufacturer will provide more detailed application and service information. Ask your supplier for an up-to-date manual. To obtain a free copy of the Alcoa Heavy Duty Wheel Service Manual, contact Alcoa Wheel Products International, 1600 Harvard Avenue, Cleveland, OH 44105, 800-242-9898.