Have you ever noticed how many laws there are? Not governmental laws, but universal laws.
Like, Murphy's Law: Anything that can go wrong will go wrong. Or the Variation Law: If you change lines (or traffic lanes), the one you were in will start to move faster than the one you are in now. Or the Law of Mechanical Repair: After your hands become coated with grease, your nose will begin to itch.
There are many universal laws like these that affect the tire industry every day. Another one is the Law of Change: Nothing is constant except change. The trucking industry is changing rapidly due to the current economic environment, driver shortage, high fuel prices and government regulations. These factors impact fleets all the way down to their vehicle specs.
With the rising price of fuel and the need to haul more freight more efficiently, more and more fleets are looking at ways to reduce costs and improve efficiency. That includes using aluminum wheels to reduce vehicle weight, lower fuel consumption, haul more payload, eliminate periodic reconditioning that steel wheels require and appeal to drivers who are in great demand and short supply.
The vast majority of aluminum truck wheels are installed on new vehicles. So with the tractor and trailer manufacturers now cranking out new equipment like there is no tomorrow, aluminum wheel sales are going through the roof, too. As a result, you are probably going to be dealing with them more than ever before. Are you ready for this change?
Aluminum wheels have some peculiarities you ought to be aware of. Tires can be mounted from either side on most aluminum wheels unlike steel wheels on which tires should be mounted only from the short side of the drop center. However, some 19.5-inch aluminum wheels have a reduced wheel well and should always be mounted and demounted from the disc side of the wheel.
Law of Scratch and Dent
The one time you can't find your wheel protector is the time the driver is watching over your shoulder. Most technicians already know that polished aluminum wheel finishes can be scratched easily and-at around four times the cost of steel wheels-truck operators want them to remain scratch free and beautiful over the course of their lives.
A wheel protector should always be used between the outer cap nut socket and the face of the wheel to prevent scratching and marring the wheel finish. For this same reason, you want to make sure you use a floor pad during manual mounting and demounting and special adapters for aluminum wheels on your tire-changing machine to prevent gouging the wheel. Do not use tire mounting machines that clamp to the inside of the rim since the clamps may gouge the rim.
Wheel guards or spacers are handy tools to use with aluminum wheels. These nylon separator discs are approximately 0.04-inch thick and are placed in the bolthole circle between the hub or drum and the wheel and/or between the two wheels in dual applications.
Their purpose is to keep corrosion or wear from occurring on the disc wheel mounting faces in severe applications and to protect the polished surfaces in less severe operations. However, when these spacers are used, care must be taken in centering them prior to torqueing the nuts. And you also have to be sure the stud is long enough to accommodate the wheel guards as well as the wheels. The stud must be long enough to allow the nut to fully thread onto the stud to ensure that proper torque is achieved.
Wheel guards and spacers must be replaced at least at every tire change and examined for serviceability when wheels are removed for routine maintenance.
Be aware that aluminum wheel protectors that you use when removing and installing wheels cannot be used for this purpose. They will compress under torque, which will result in loose wheels.
Law of Rust
If there is moisture, there will be corrosion. That's the law.
Many people don't think aluminum wheels will corrode, but they do. While aluminum has a natural resistance to corrosion and does not need to be painted, aluminum wheels will corrode in severe service environments where salt and chloride compounds are used heavily for snow removal.
You can find air leaks at the valve hole of aluminum wheels due to corrosion at the grommet or O-ring in addition to corrosion in the bead seat area of the rim. This is often caused by entrapped moisture, which contains corrosive elements and can be carried by moisture-saturated inflation air or from water left in the tire.
Therefore, it is necessary to lubricate valve stems installed in aluminum wheels with an anti-corrosive compound. The lubricant should be applied to the valve stem threads and O-rings prior to installation. This will prevent corrosion from occurring around the O-ring, which squeezes the O-ring and causes leaks.
After removing the corrosion with a wire brush, also coat the rim surface to protect it. This lubricant not only must resist corrosion, it also must be resistant to high temperature. Do not use anti-seize compounds.
Law of Nature
Size is important. Since aluminum wheels are about double the thickness of steel wheels, special considerations must be given to their studs and nuts. In stud-piloted systems, if you have to replace a stud on a vehicle with aluminum stud-piloted wheels, you should know that single aluminum wheels on 3/4-inch studs use different nuts than steel wheels. They use a collared single nut.
Dual aluminum wheels require special inner nuts with greater strength and length than steel wheel inner nuts. While you can use standard outer cap nuts for both steel and aluminum wheels, use only Grade 8, collared, inner cap nuts for aluminum, dual-wheel applications. For mounting steel inner wheels with aluminum outer wheels, special longer length, non-collared inner cap nuts are required.
For vehicles with hub-piloted wheels, longer hub pilots are required for centering dual aluminum wheels. The pilot should extend through 50 percent of the disc thickness of the outer dual wheel. The same flange nuts are used as for steel disc wheels, but make sure the studs are long enough to fully engage the flange nut threads.
Here's a question that keeps coming up: ``How far past the nut should the stud extend to fully torque the nut?''
The answer is that all the nut threads must be screwed on the stud. Any part of the stud extending past the nut isn't doing anything. However, if the stud is not long enough to engage all the nut threads, clamp load will be reduced. This is true for aluminum as well as steel wheels.
As far as service conditions go, aluminum wheels tend to have fewer problems than steel wheels. Since they don't have any welds, butt weld leaks or attachment (disc to rim) weld cracks are not an issue. But you should still look for cracks at the valve stem hole, boltholes and hand holes, and wallowed or elongated stud holes, as you would in steel wheels.
Law of Experience
If you think you've seen it all, you're about to be surprised.
A condition that is unique to aluminum wheels is rim flange wear. This is a condition in which abrasive wear or pitting develops on the top of the flange all around the rim. It is usually found on wheels in heavy load operations although general freight haulers sometimes see this as well. It occurs as a result of the tire chafer and sidewall wearing away the top of the rim flange during use.
As the tire rotates, the sidewall flexes and contracts as it rolls through its footprint. The cyclic loading of the tire and flexing of the tire sidewall create a ``scrubbing'' or erosion type wear on the wheel rim flange. Operating conditions-including load, inflation pressure, tire size, tire type and tire construction-have significant impact on whether and at what rate rim flange wear occurs.
In many operations it never occurs even after years of service. However, when it does show up, it can create a sharp edge on the aluminum wheel, which can cut the lower bead area of tires. Wheels that run in corrosive or abrasive environments may experience severe flange wear. Shifting loads such as those common in tanker operations also exaggerate this condition.
Moderate and even severe rim flange wear is a normal operating condition. Aluminum wheel rim flanges should be inspected for wear and sharp edges every time a tire is demounted. If wear is observed, use a rim flange wear gauge to determine if the wheel must be removed from service for excessive rim flange wear.
If the rim is still serviceable according to the gauge, the sharp edge can be removed with a file, or an air- or electric-powered sander or grinder.
Care must be taken to maintain a uniform edge and avoid gouging the wheel. The amount of metal to be removed is small and will vary based upon the condition of the wheel and the severity of the rim flange wear. The idea is to remove just enough aluminum to smooth the edge. After the edge is removed the rim flange wear gauge should be used again to ensure there is adequate flange height remaining to safely support the tire bead and sidewall around the circumference.
If the entire rim flange is within the limits of the rim flange wear gauge, the wheel may be returned to service.
You can get a free rim flange wear gauge(s), detailed instructions and more information on rim flange wear by calling Alcoa Wheel Products at (800) 242-9898 or going to www.alcoawheels.com.
While aluminum wheels certainly require less maintenance than steel wheels, as you can see, they do require some special considerations. You'll find that in dealing with them the following universal laws will prevail:
The Law of Tire Service: A lug nut, when dropped, will roll under the least accessible area of the truck (or shop);
The Tire Shop Inspection Law: You will run out of bead lubricant at exactly the same time your big fleet account arrives for a shop inspection; and
The Aluminum Handhole Rule: Anything you can force through an aluminum handhole (like your hand), must come out the same way.