Staying Straight

Rich Manapat of Complete Diesel Service uses a jacking system to raise the front axle off the wheels, which allows proper checking of front-end components.

Why should you pay attention to wheel alignment?

“Alignment is just one thing you can do to reduce tire costs,” says Doug Jones, a customer support manager at Michelin. “Tires are designed to go down the road facing straight ahead. Misalignment will reduce the life of the tire via irregular wear and interfere with handling.”

If tires always went straight down the road, Jones says, they’d last “practically forever.” But acceleration and braking multiply wear tenfold, and lateral forces from steering or misalignment multiply wear even more – as much as 500 times. “It’s a scrubbing type of action,” Jones says.

Tire wear is just one issue caused by misaligned wheels. Fuel consumption and handling are also affected. Precision alignment may cost upward of $230 for all the wheels of a straight truck or tractor, but it more than pays back in comfort and cash.

Because tire and fuel costs top the list of owner-operator expenses, getting your tires aligned can save a lot of money, especially if it keeps you from having to replace your steer tires every six months. Misaligned wheels fight one another. Incorrect toe-in is the most common form of misalignment, but whether the problem is front wheels running toed-in or toed-out, or an axle (even on the trailer) that isn’t tracking straight, the result is one or more tires scrubbing sideways.

Even a small problem can lead to tread-life loss. If an axle is misaligned by only the thickness of a dime, it causes scrubbing equivalent to pulling the tire across six feet of concrete every mile, according to testing done by Hunter Engineering.

“The tread should be smooth all the way across,” says Al Cohn, a technical marketing manager at Goodyear. “Sharp edges that you can feel typically mean wear from toe-in or toe-out.”

Irregular wear from misalignment often condemns a tire to the scrap heap before the tread is worn. In fact, misalignment wear can damage the tire casing itself; even if you don’t retread, you can get money for the casing when you replace the tire.

Fuel consumption is also a big problem when the wheels are out of whack because scrubbing adds to rolling resistance. Misalignment can cause a trailer to dogtrack, which burns more fuel because the trailer becomes a bigger target for the wind, says Mike McCoy, regional manager with Bee Line Co., which makes alignment machines.

Also, improper alignment can severely affect handling and can increase fatigue, says Guy Walenga, an engineering manager at Bridgestone/Firestone.

“Do alignment for your own sake,” Walenga says. “You’ll feel much better after a long day behind the wheel when the wheels are aligned.”

Misaligned wheels will cause you to keep your hands cocked to the left or right just to steer. “You’ll be doing a lot of extra work to keep the truck on the highway if alignment isn’t correct,” Cohn says. Vehicle handling in a panic situation can also be greatly improved if wheels are properly aligned.

Wheels must be aligned to within an extremely small tolerance, or excessive wear and uncertain handling will result. A tiny bit of suspension component wear puts the wheel at the wrong angle, with disastrous results.

When technician Rich Manapat at Complete Diesel Service in Essington, Pa., recently realigned a nearly new Kenworth dump truck, he got an indication that camber was out of specification. The culprit was a left front wheel bearing that was slightly loose.

Truck makers do a good job of designing vehicles to stay aligned, says Doug Woolverton, northeast division manager for Hunter Engineering. But all the components that connect wheels to the truck – from tie rod ends to kingpins, spring shackles and rubber grommets – wear as you drive down the road. “Wear occurs even without an accident,” Woolverton says.

Wheel alignment can be a circular problem: Component wear can cause a vehicle to go out of alignment, and misalignment can cause component wear, Woolverton says. Obviously, dragging wheels sideways puts unnecessary stress on parts such as wheel bearings, tie rods and suspensions.

Front axle alignment is maintained by checking toe-in, camber and caster. On the rear axle, tracking must be checked. The proper tracking of the wheels in a turn, called the Ackerman angle, may also be checked to make sure you don’t have a bent suspension component.

The trailer axles must be aligned so that tracking is correct. A dogtracking trailer will still cause irregular wear on perfectly aligned tractor tires.

“Steer tires will be affected regardless of what is out of alignment,” Walenga says.

To find a good alignment shop, ask other owner-operators where they go and consult your tire dealer. The type of equipment in a shop can be a good indicator of its expertise, McCoy says. “If they have an alignment machine that raises the truck up off the floor, they’re really in the alignment business.” A training certificate from the supplier of the equipment is also a good sign, he says.

Understanding the sensitivity of the equipment and the need to recalibrate is critical, so ask how often the shop recalibrates. Manapat says he recalibrates his machine every 15 alignments.

Alignment should be checked and, if necessary, reset at least twice a year. Every 80,000 miles is a good interval, but you should also have your truck inspected if you notice problems. With a big rig, any toe-in or toe-out problems will show up quickly, says Toyo’s Ron Gilbert. “You’re going to notice a problem pretty fast.”

“Wander and pull are dead giveaways,” Jones says. “Look in the mirror at the trailer, too, to see how it’s tracking. And feel the tires for irregular wear.”

A complete alignment for tractor and trailer can cost hundreds of dollars. Complete Diesel Service, for example, charges $150 to set up and check alignment and set toe. If camber or caster need correction, that adds $50 per correction. A tandem axle trailer can be aligned for $85.

Still, the cost should be worth it. “With a set of steer tires costing $600, it’s foolish not to set alignment,” Manapat says.

“At about $200, if you can save just one tire from an early demise, alignment has paid for itself,” says Michelin’s Jones. “You’ll also save fuel and improve your operating safety.”

Axle bending is often not the right cure for an alignment problem, and the job is often performed improperly. But precision equipment does exist for bending axles to “correct” them.

The key is proper training and equipment. Bee Line Co.’s Mike McCoy says the axle is bent only a tiny amount without being heated. Complete Diesel Service’s Rich Manapat was taught to bend the axle using precision equipment capable of creating 130,000 pounds of controlled force. Good techs can measure the needed change in the axle and bend it “just past the yield point, so it will spring back to just the right position,” Manapat says. This can mean a better camber adjustment and longer steer tire life.

Truck makers discourage bending the axle, however, and doing so often voids the axle warranty. If an axle is seriously out of alignment, it should be replaced.

When your truck goes up on an alignment machine, the technician looks for several things:

TOE-IN OR TOE-OUT: The distance between the steer tires at the front versus the rear. The toe is set with the steering centered and the fronts of the tires toed in a tiny amount – about 1/16 of an inch “total toe.” This actually results in running straight ahead under loaded conditions when the truck is moving. Toe-in, the most commonly adjusted alignment parameter, is changed by rotating the tie-rod tubes, which are threaded.

THRUST ANGLE: The angle between the drive or trailer axles and the tractor or trailer frame. The thrust angle should be zero degrees.

SCRUB ANGLE OR TRAM ANGLE: The angle between axles on either the tractor or trailer. Unless axles are parallel, tires will fight each other, even if the net effect is a thrust angle of zero. After toe-in, thrust angle and scrub angle are the most critical settings for tire wear and should always be set along with the steer axle.

CAMBER: The angle formed by wheels being tilted in or out at the bottom. The wheels are supposed to run as vertically as possible. The American Trucking Associations’ Technology and Maintenance Council recommends camber of less than one-quarter-degree empty, which compensates for axle bend as the vehicle is loaded.

Camber problems usually result from a loose wheel bearing or bent spindle. Axle damage and manufacturing problems can also disrupt camber.

If a camber problem can’t be adjusted or repaired, bending or replacing the axle is an option.

CASTER: The slight tilt of the upper end of the kingpin for giving directional stability to the front wheels. The steering knuckle turns on the kingpin the way a door turns on its hinge pin; positive caster means setting the kingpin at an angle so the truck is lifted slightly when you turn. Caster has no effect on tire wear but a major effect on the steering stability and self-centering characteristic of a truck, says Mike McCoy of Bee Line Co.

Showcase your workhorse
Add a photo of your rig to our Reader Rigs collection to share it with your peers and the world. Tell us the story behind the truck and your business to help build its story.
Submit Your Rig
Reader Rig Submission