Successful wheel service specialists always follow proper preliminary procedure before doing an alignment, experts said. Proper procedure includes interrogating the driver and road testing the vehicle carefully. Getting accurate symptoms and vehicle history from the driver is critically important in every area of automotive service today. Spending a few minutes now collecting this information saves countless hours of diagnostic time later on because many tire/wheel/suspension problems create the same or similar symptoms.
Wheel alignment pros agreed that questioning the driver remains one of the most overlooked parts of proper procedure. Typically, the consumer still defines the need for wheel alignment by default. That is, he notices a symptom, concludes that wheel alignment will correct the condition and schedules an appointment at a tire dealership or service shop. Then service personnel fail to ask the essential question: ``Why do you think your vehicle needs an alignment?''
For example, experience shows many motorists assume every shimmy-like symptom automatically requires wheel alignment. Actually, shimmy is almost always related to a tire/wheel problem such as imbalance, an out-of-round or damaged tire or a bent wheel.
Technically, an extremely sloppy wheel bearing or severe wear in the steering linkage or a steering pivot can cause a shimmy. But by the time these parts are worn enough to cause a shimmy, the symptoms also include a severe wander or steering pull-so severe the driver usually says the vehicle feels downright unsafe on the highway!
Also, many consumers and automotive technicians automatically think ``alignment'' whenever a vehicle pulls to one side of the road. But it's not uncommon for a defective or damaged tire to cause a pull. That's why service personnel should instinctively swap the front tires side to side whenever a driver complains about a pull. If swapping the tires side to side makes the vehicle pull in the opposite direction, it confirms the condition is tire-related.
Most tire dealers agree tire quality is consistently better than ever, so they see fewer tire-related pulling conditions. Unfortunately, some said they see so few tire problems that when a pull occurs they forget the most fundamental check: Swap front tires side to side.
Tire dealers who use diagnostic symptom sheets said prompting the driver to describe the condition in writing speeds up troubleshooting by helping them zero in on possible causes. Without a symptom sheet in front of them, some drivers have difficulty describing a handling problem verbally. The best they offer may be, ``The car feels scary or unstable.''
A good symptom sheet also reminds a driver to indicate if the condition occurs constantly or just some of the time. When the problem occurs some of the time, the questionnaire should offer the motorist several possibilities (for instance, only when applying the brakes, only when driving over a dip, only when crossing railroad tracks etc.) to choose from as well as a space to enter his own description.
Suppose the driver confirms the car only feels unstable when it goes over a dip in the highway. Savvy service personnel know this indicates a potentially dangerous condition called bump steer. If nothing else, this prompts a technician to pay closer attention to the vehicle's reaction to dips during a road test.
Plus, an effective diagnostic symptom sheet helps clarify critical terms for consumers. For example, experience shows some drivers use the words ``pull'' and ``wander'' interchangeably. However, pull refers to a camber- or caster-related condition in which a vehicle always drifts toward the same side of the road when you release the steering wheel momentarily or else maintain a light finger-tip grip on the steering wheel.
On the other hand, wander describes a toe-related problem where the vehicle drifts to one side of the road one time and to the opposite side another time.
Whether or not you use a symptom sheet, always ask if the symptom began after other repairs were done to the vehicle. Often, double checking those repairs reveals the root of the current problem.
Smart wheel-service specialists always perform a pre-alignment road test over a known route containing a variety of realistic road conditions, including dips and bumps, a railroad crossing, sharp curves, smooth and coarse roadways etc. Unless the route exercises the suspension thoroughly, it may not reveal the symptom or clue needed to diagnose the vehicle quickly and accurately.
Following the same route offers a basis for comparing known-good cars to problem ones.
What's more, using a standard road test route makes it easier to find someone when those inevitable mechanical breakdowns or inoperative gas gauges strand service personnel on the roadside!
Ultimately, road testing saves time by confirming the clues presented on the symptom sheet. Obviously, road testing-especially with the customer on board-becomes doubly important when no symptom sheet is available as a diagnostic guideline.
When road testing, remember that alignment-related problems usually fall into two general categories: Pull and wander. Earlier, we described how to diagnose a tire-related pull. But assuming the tires are not the cause, camber and caster-related problems cause pull, toe-related
trouble causes wandering. (Camber, caster and toe are discussed elsewhere in this service section.)
Be alert for multiple symptoms. By the time the vehicle reaches your service department, it may have several things wrong with it. Not only is this an opportunity to sell more legitimate repairs, it's a situation that invites comebacks when service personnel aren't attentive and thorough. Plus, this underscores the value of a thorough road test.
The reason is one steering/
suspension symptom may capture the driver's attention, causing him to forget or overlook other symptoms you should know about and investigate. When this happens, the success of the diagnosis depends even more on the skill of the person(s) road testing the vehicle and performing the pre-alignment undercar inspection.
For instance, severely worn steering linkage could cause a combination of wander and shimmy. Upon road testing the car, you notice extremely sloppy steering and a vehicle that wanders so much it requires constant steering corrections. Meanwhile, the driver seems fixated on a wheel shimmy that occurs after the car hits a bump.
Sometimes shimmy instigated by a severely worn component doesn't occur until a bump aggravates the looseness, causing a tire to oscillate or vibrate. Incredibly, the shimmy may become more of a concern to the driver than the incessant drifting and wandering!
Don't rush to judgment when a vehicle only pulls during braking. Common brake trouble could be the culprit. But many service technicians forget that when worn parts allow a severe caster change during braking, the vehicle will pull toward the side having the least amount of positive caster. Worn or fatigued strut/radius rod bushings are a common cause of caster change and caster imbalance during braking.
Finally, don't confuse wheel imbalance with binding drive axles. Fatigued motor mounts can allow the drivetrain to sag enough to disrupt the drive axles' normal operating angle. This forces the inner constant velocity (CV) joints to bind up, causing a vibration that's often noticeable only at low road speeds.
Although this doesn't match routine wheel imbalance symptoms, some service technicians blame imbalance because they can't pinpoint any other cause.
Also, some vehicles such as Chrysler products have adjustable engine mounts. If another shop performed certain drivetrain repairs without readjusting the engine mounts, the inner CV joints may bind up, creating a vibration.
In this case, gathering an accurate vehicle history would save untold time tracing a relatively unfamiliar problem.