Ensuring appropriate alignment
Vehicle alignment is an integral maintenance issue
Vehicle alignment settings serve a variety of functions in vehicle operation and affect, among other things, handling, steering, stability, performance and safety. Research has shown that total vehicle alignment maintenance and inspection programs can pay dividends in extended tire wear for increased tire mileage, enhanced fuel economy, decreased component wear, greater uptime, improved driver comfort and safer vehicles. Nevertheless, industry experts estimate that 70 to 80 percent of Class 8 trucks on the road today have alignment problems.
The chassis serves as the foundation of the vehicle and it needs to be square and solid to support the dynamics of the complete structure. The chassis includes each wheel, axle, suspension component and frame member, and all should be aligned in relation to one another as a whole.
A vehicle that is not in proper alignment affects every aspect of operating costs per mile with the two largest maintenance expenditures — tires and fuel — affected the most. Misaligned axles and tires cause the tires to be scrubbed across the pavement, increasing rolling resistance, which directly impacts fuel consumption. Such unnecessary lateral forces not only require more horsepower to move the same load, but they also significantly reduce tire mileage, resulting in more frequent tire replacement.
What’s more, a vehicle going down the road with improper alignment negates all of the aerodynamic aids added to it to slice through the wind efficiently.
Five major issues occur as a consequence of alignment issues, says Mike Beckett, president of M.D. Alignment Services, Des Moines, Iowa, a company that offers alignment equipment for heavy trucks and trailers as well as alignment training and consulting. In his book, “Truck Wheel Alignment: A Common Man’s Guide,” Beckett provides basic guidance to solving all the major aspects of vehicle alignment and tire wear. Those major issues are as follows:
- Feathered tire wear: A condition where tread ribs or blocks are worn as such that one side is higher than the other, resulting in step-offs across the tread face. This is commonly caused by drive axle misalignment or by toe, which is the difference in distance between the front and rear of the steering axle tires as seen in a top view of the truck.
- Cupping tire wear: Localized, dished-out areas of fast wear that create a scalloped appearance around the tire, usually on the shoulder ribs. Common causes are improper tire inflation and/or balance, a mismounted tire or rim, a bent rim, feathered wear, loose components, a tall tire/short tire combination, excessive speed and lightweight axles.
- Right pull: Usually caused by drive axle misalignment, a twisted frame or steering gearbox problems.
- Vibrations: Typically caused by driveline issues, loose bearings, out-of-round tires, balance issues, or toe or drive axle misalignment.
- Road wander: Generally caused by toe-out, which is a condition that exists when the tires are closer together in the rear than in the front, steering linkage problems or loose rear suspension components.
Beckett says misalignment can cause premature wear or failure of shocks, springs and pins because of excessive oscillation caused by tire hop or vibrations.
Improper vehicle alignment also has an effect on drivers. When a vehicle is not in alignment, the driver constantly is correcting the steering wheel, and they could eventually get tired and frustrated with the constant correction and, therefore, become less effective, productive and safe.
Some fleets have found that measuring and correcting alignment for all power units and trailers as a part of their preventive maintenance program helps to maintain effective cost per mile expenditures for both fuel and tires.
Alignment checks at regular intervals are necessary, they say, because vehicle suspensions are flexible and, therefore, the alignment will change due to the G forces emitted by the powertrain. Regular alignment checks enable correction of any adverse changes in the vehicle geometry due to wear and tear.
Manufacturers of vehicle alignment equipment say the choice that a fleet must make is whether to be proactive with a dedicated alignment program or be reactive and align a vehicle when tire wear takes place and is obvious. One method maximizes a vehicle’s tire life and fuel economy, and the other does not, they say.
The Technology & Maintenance Council (TMC) of the American Trucking Association developed a Recommended Practice (RP) on total vehicle alignment: RP 642A or “Total Vehicle Alignment: Recommendations for Maximizing Tire and Alignment-Related Component Life.” The RP presents guidelines and procedures that can be used to maximize tire tread life and minimize total tire-related expenses on Class 7 and 8 commercial vehicles.
It also provides procedures to identify, record, document and analyze alignment issues as well as offer guidance on selecting and evaluating both alignment equipment and service providers. RP 642A is included in the TMC 2012-2013 Recommended Practices Manual, which is a comprehensive reference for maintenance personnel, technicians, engineers and suppliers. It can be ordered by phone at 866/821-3468 or on the Web at http://atabusinesssolutions.com. BI