Straight shooting:Total alignments will protect tires, save fuel
January 1, 2006
TORONTO, Ont. - Keeping a truck "between the lines" requires a combination of skill and concentration, but it's a proper alignment program that will keep your tires on the straightest path of all, ext...
TORONTO, Ont. – Keeping a truck “between the lines” requires a combination of skill and concentration, but it’s a proper alignment program that will keep your tires on the straightest path of all, extending tread life and limiting struggles with the steering wheel.
“Most poor alignment conditions – even on drive axles – will cause irregular (tire) wear,” says Goodyear strategic account manager, Al Cohn.
Indeed, it’s time to forget any idea of “set the toe and go.” Fleets and owner/operators should adopt total vehicle alignment programs to enjoy the full advantages that the maintenance practice can offer, speakers suggested during a recent Technology and Maintenance Council meeting in Toronto.
A proper alignment has the potential of increasing tire life by an average of 30 per cent, says ArvinMeritor service manager Michael Bryan.
So too can the practice deliver a two per cent increase in fuel economy – a benefit that’s particularly important given recent sacrifices made in the name of cleaner emissions.
Granted, every new vehicle is properly aligned before it’s sold.
“An OEM factory alignment may be one of the best a vehicle will ever get,” Bryan says, referring to the way manufacturers use the latest equipment, calibrate it to meet ISO standards, and complete the measurements under ideal conditions, rather than fighting with the rusty, dirty and over-painted components that are a reality in a fleet yard.
But the alignment work can’t end there.
The maintenance practice should be completed within a truck’s first 15,000 and 30,000 miles (24,000 and 48,000 km), or no longer than 90 days after it’s purchased, he says. Subsequent alignments should occur within 80,000 and 100,000 miles (about 150,000 km), or every 12 to 18 months.
If those benchmarks are missed, the initial signs of troubles can emerge in the form of unusual tire wear, or lost fuel economy.
In general, toe and thrust settings are the most critical to protect tires from premature wear, says Cohn, noting that camber and caster are lesser issues.
The toe refers to the direction tires are pointed when compared to the centerline of the truck, as if you were looking down on it from the air, while the thrust angle refers to the different directions that axles may be facing.
If you’re facing the front of a truck, the camber angle describes how far the tire will slant from a perfectly vertical position. And if viewing a vehicle from the side, toward the wheel’s hub, the caster identifies the forward or backward slope of the steering assembly’s pivot points.
If there is too much “toe in” – with a truck looking like it is pigeon-toed – a tire’s outside shoulder will quickly wear out. Too much caster, meanwhile, will cause a truck to wander all over the road.
Optimal toe settings should ensure that opposing steer tires are between 0 and 1/16 inches of each other, while drive tires need to be within 1/8 inch of those on the other side of the axle, says Maitland Gillespie of Hunter Engineering, which supplies alignment systems.
In most cases, that means the overall toe angle should be 0.08 degrees. (Rack and pinion steering systems require individual toe settings of 0.04 degrees. And “it’s coming” in the world of trucks, he adds.)
Still, a proper alignment for a late-model truck won’t necessarily position a tire at exactly 90 degrees to the road. Some suspension systems incorporate a positive camber – with both wheels tilting outward at the top – to ensure a smoother ride, and then sit in an upright or “zero” condition once a vehicle is loaded, Gillespie says. Caster may also need to be increased to compensate for air-ride suspensions, to aid in cornering. In contrast, light-duty vehicles will often include a negative camber in the name of performance.
“If both outside shoulders (of opposing tires) have fast wear…that’s thrust-angle related,” Cohn adds.
Proper alignments can even play a role in driver satisfaction, Bryan suggests, referring to a study of public works drivers in New Brunswick in the early ’90s, which suggested a link between the number of hours in the driver’s seat, and the time when fatigue sets in place.
Companies that have long followed the same alignment procedures may also want to check if they’ve adopted acceptable tolerances that changed in the early ’90s, Bryan says.
Tandem scrub angles for wheels on opposite sides of a truck now need to be within .100 of an inch of each other, while thrust and steering angles need to be within 0.70 inches.
Keep in mind that alignment problems can even fail the Commercial Vehicle Safety Alliance’s out-of-service criteria. In this case, inspectors are looking for problems such as more than 1/8 inch of movement between a steering linkage member and its attachment.
While the focus of alignment programs has traditionally been on tractors, there are also benefits to trailer alignments – even though they are seldom completed, Bryan admits. (“I don’t normally see one being done. I don’t normally hear of one being done unless it’s been in an accident.”)
And regardless of any sophisticated equipment that’s used, it’s also important to occasionally grab string and a tape measure to confirm an alignment system’s readings, he adds.
“It doesn’t take much time to confirm what you’ve done on a sophisticated piece of alignment equipment.”
Equally, it’s important to find the right shop to do any work that you require.
“We do need quality people to do this,” Bryan says. “It is a fairly technical job.”
The first step in choosing a shop will involve investigating its reputation, which can require calls to a few of its existing customers, says Brian Strach of Hendrickson.
Do they minimize tread wear? Do they offer rear-axle alignments? (If not, the shop doesn’t offer total vehicle alignments.) And do they offer trailer alignments on site? For that matter, are technicians licensed to conduct test drives?
“And if a shop looks at you and says, ‘Why do I need to calibrate (equipment)?’ you better run.”
Technicians should also be certified to use specific equipment, or address individual components such as tie rod ends and shocks, he says.
The alignment, after all, is only part of the equation. A shock that’s oozing oil needs to be replaced.
If a tire is simply changed without addressing the root cause of a problem, you’re burning rubber for no reason at all.
It may all seem like extra work, but there is an alternative, Bryan says with a smirk.