The ins and outs of wheel alignment
Correcting the specific angles of wheels can reduce tire wear and eliminate pull
One of the most recommended services drivers face during spring check-up is wheel alignment.
With the constant onslaught of pothole perils, it’s easy to understand why steering adjustments are popular repairs. But it is well to know the right questions to ask at the service counter.
One of the most common misunderstandings is that wheel alignment and wheel balancing are different things.
Wheel balancing is usually performed to rectify high speed vibrations and it involves removing the wheel and tire assemblies one at a time, mounting them to a specialized piece of shop equipment which spins them at high speed, indicating where lead weights need to be added and in which mass. These weights are then installed and the wheel is spun one more time to confirm it is balanced.
Wheel alignments, on the other hand, involve correcting specific angles of the front and rear wheels to improve tire life, reduce rolling resistance and eliminate the wear on drivers who may be constantly fighting a pull on the steering wheel.
Usually, drivers notice first a constant steering pull. Then come uneven tire tread wear and a tendency of the car to wander. Very few vehicles exhibiting these symptoms ever need just a simple alignment adjustment.
If any one of the three critical specs in a wheel alignment is out of tolerance, it’s usually due to a bent or damaged steering or suspension part, or excess wear on one of these components leading to free play.
The first measurement (and the one that requires the most correction) is wheel toe-in or toe-out.
Simply put, the front wheels on any vehicle are not configured to follow a perfectly parallel path. Most car makers call for them to toe-in slightly, which means the centres of the leading edges of the front tires are closer together than the rear.
This is to provide steering stability because if the wheels were perfectly parallel the steering wheel would need constant and frequent adjustments to keep the vehicle on a straight path.
The parts on a vehicle that contribute most to keeping this measurement correct are the steering gear, the outer tie rod ends (where the steering gear is connected to the wheel units) and any of the linkages that connect the tie rod ends to the steering gear. These parts can easily be damaged when a wheel slides into a curb or other solid object, striking it laterally.
Every car maker provides threaded adjustments on at least the outer tie rod ends to allow a tech to put things right to a very narrow tolerance.
Next comes wheel camber, which is its vertical angle. Negative camber refers to a wheel that’s “tilted” in slightly at the top and positive camber is the term for a front wheel tilted out. These configurations allow the suspension to travel up and down over bumps without drastically changing the amount of contact a tire has on the road. They also lead to steering stability.
Camber problems usually lead to uneven tire wear on the inner or outer tread face and are most often caused by worn ball joints (the pivot points that connect the wheel unit to the suspension).
Not all car makers provide readymade adjuster mechanisms for this setting, realizing that camber only goes out of kilter when a ball joint requires replacement, or when a substantial impact has bent a control arm or suspension strut.
However, those vehicles with adjusters usually have eccentric bolts connecting the lower part of the strut to the wheel knuckle. Those without any type of adjuster may require modifying the inner fender to permit a change in this angle.
Next is caster. If you could easily view the line through the front strut from top to bottom on a vehicle with positive caster, the top of the strut would be tilted back, and on one with negative caster it would be tilted forward.
Hitting the leading edge of a large deep pothole with the front face of your vehicle’s front tire at a good speed can be a good way to upset this spec. Caster angles almost never have an easy mechanical adjuster and can be the most expensive to reset.
When considering a wheel alignment repair estimate, ask whether or not the component being proposed for replacement has wear in excess of the auto manufacturer’s specs.
Ball joints, for example, usually have a published tolerance and while few car makers allow for any horizontal play, many will permit some vertical movement.
When larger, more expensive components such as steering gears are being recommended for replacement, ask if a remanufactured or quality after-market substitute is available rather than new (especially on an older vehicle).
Nothing answers all your questions better than having a tech point out the problems directly to you with the vehicle on the hoist.
In light of the sometimes high costs of these repairs, it would well be worth your time. Send questions to Troubleshooter, Ottawa Citizen, 1101 Baxter Rd., Ottawa, K2C 3M4. Fax: 613-726-1198. E-mail: firstname.lastname@example.org . Specify your vehicle’s model, engine and odometer reading, and provide your full name, municipality and daytime phone number. We are unable to provide individual replies.