Wheel alignment is a traditional customer concern that usually involves abnormal tire wear or handling discrepancies -- such as pulling, poor tracking, or steering wheel angle -- that customers can easily see or feel. However, as with many repairs, the symptoms that customers experience don't always point toward the root cause.

In many cases, a wheel alignment is not the best place to start for a wheel- or suspension-related concern. Simple items to check include tire pressure, road slope or crown, and possible damage caused by impact to the vehicle.

Proper diagnosis always begins with a road test. Check the condition and operation of other components on the vehicle, which can indicate whether a wheel alignment will correct the condition. Plus, verify the vehicle is in Original Equipment condition for curb weight, tires, wheels and suspension configurations. Any alterations can affect vehicle performance.

A common wheel alignment symptom is a lead/pull condition, which is the amount of effort required at the steering wheel to maintain the vehicle's straight heading at a constant speed on a straight road. Correcting this condition may require a wheel alignment, but also keep in mind road slope or road crown.

As a part of normal operation, vehicles will follow side-to-side road slope or road crown. So, first check with the customer about the types of roads that are being driven. Some drivers do not recognize the influence of road slope on vehicle lead/pull. (Fig. 2)

Fig. 2

Roads typically have some degree of crown or slope to allow for rain run-off. Vehicles are designed to compensate for a slight amount of road crown, but evaluating a vehicle on the wrong roads can lead to improper diagnosis. Perform a test drive on actual roads, not in a parking lot, to get a real world impression of the vehicle's behavior in right and left sloping lanes. For example, if testing the vehicle for a "leads to the left" concern, evaluate the concern in the left lane as well as in the other lanes. If the vehicle quickly climbs the road crown, then it may have an issue that needs to be looked into further.

In addition, a lead/pull condition when holding the steering wheel in a level position may be caused by a steering wheel angle condition. In this case, the driver is steering the vehicle to obtain a level steering wheel, resulting in the lead/pull effect. Steering center is that the steering wheel is centered and level when the vehicle is traveling down a straight and level road. If the car is not pulling, then steering center is controlled by the front and rear toe settings. Be sure to road test the vehicle after any repairs.

Steering and vibration complaints are not always the result of improper alignment. One possible cause is wheel and tire imbalance. Tires should all be in good shape with even wear patterns. Slight "feathering" or "edge" wear on the shoulders of tires is not unusual and should even out with a tire rotation. (Fig. 3)

Fig. 3

Be sure to understand the customer's driving habits as this will also heavily influence the tire wear performance. Also check that tire inflation pressure is being maintained.

Trim height -- the distance between the vehicle's frame and the road -- is the reference point for all alignment measurements. Incorrect trim height can cause bottoming out over bumps, damage to the suspension components and symptoms similar to wheel alignment problems. There is no adjustment procedure for trim height. Check for improper weight distribution, collision damage, and worn or damaged suspension components, all of which can alter a vehicle's geometry and create misalignment. 

Worn suspension parts, such as worn struts/springs, can lower the trim height and often cause alignment problems.

Another common condition is worn ball joints, which can result in poor handling, slow steering response, and irregular tire wear. Also, worn steering tie rods can lead to tire feathering by allowing the tire to wander left to right, effectively changing toe as the vehicle rolls down the road.

Other repairs that affect wheel alignment include control arm replacement, engine cradle adjustment or replacement, steering gear replacement, and steering knuckle replacement.

If it's determined that a wheel alignment is required, perform the following inspections and adjustments in order to ensure correct alignment readings:

• Inspect the tires for the proper inflation and irregular tire wear
• Inspect the runout of the wheels and the tires
• Inspect the wheel bearings for backlash and excessive play
• Inspect the ball joints and tie rod ends for looseness or wear
• Inspect the control arms and stabilizer shaft for looseness or wear
• Inspect the steering gear for looseness at the frame
• Inspect the struts/shock absorbers for wear, leaks, and any noticeable noises
• Inspect the vehicle trim height
• Inspect the steering wheel for excessive drag or poor return due to stiff or rusted linkage or suspension components
• Inspect the fuel level. The fuel tank should be full or the vehicle should have a compensating load added

Also consider any excess loads, such as tool boxes, sample cases, etc., that may be normally carried in the vehicle. These items should remain in the vehicle during alignment adjustments.

If working on a vehicle requiring a 4-wheel alignment, set the rear wheel alignment angles first in order to obtain proper front wheel alignment angles.

Alignment machines must be regularly calibrated in order to give correct information. Most manufacturers recommend the following:

• Alignment machines with "internal reference" sensors should be checked (and calibrated, if necessary) every six months
• Alignment machines with "external reference" image-based camera technology should be checked (and calibrated, if necessary) once a year
• Racks must be kept level to within 1.6 mm (1/16 in).
• If any instrument that is part of the alignment machine is dropped or damaged in some way, check the calibration immediately

Check with the equipment manufacturer for the recommended service/calibration schedule.

Finally, prior to making any adjustments to wheel alignment on a vehicle, verify that the wheel alignment specifications loaded into the wheel alignment machine are up-to-date by comparing them to the wheel alignment specifications for the appropriate model and model year.