Alignment: Description and Operation

Wheel Alignment Angles

F-Super Duty vehicle caster and camber correction requirements are factory determined. Adjusters are available to correct a caster/camber measurement that does not meet specification. Before changing the production caster/camber adjuster, thoroughly inspect the suspension system to locate worn or damaged components that may have caused the setting to change.

Camber

Negative and Positive Camber





Camber is the vertical tilt of the wheel when viewed from the front. Camber can be positive or negative and has a direct effect on tire wear.

Camber split = LH camber - RH camber.

Caster

Caster and Steering Axis










Caster is the deviation from vertical of an imaginary line drawn through the ball joints when viewed from the side. The caster specifications will give the vehicle the best directional stability characteristics when loaded and driven. The caster setting is not related to tire wear.

Caster split = LH caster - RH caster.

Toe

Positive Toe (Toe In)





Negative Toe (Toe Out)





Incorrect Thrust Angle (Dogtracking)










Incorrect thrust angle (dogtracking) is the condition in which the rear axle is not square to the chassis. Heavily crowned roads can give the illusion of dogtracking.

The vehicle toe setting:

- affects tire wear and directional stability.

- must be checked after adding aftermarket equipment, such as a snowplow or body.

When the wheels are turned in toward the front of the vehicle, the toe is positive (+) (toe in). When the wheels are turned out toward the front of the vehicle, the toe is negative (-) (toe out). This is measured in degrees, from side-to-side, and totaled.

Wander

Wander is the tendency of the vehicle to require frequent, random left and right steering wheel corrections to maintain a straight path down a level road.

Shimmy

Shimmy, as observed by the driver, is large, consistent, rotational oscillations of the steering wheel resulting from large, side-to-side (lateral) tire/wheel movements.

Shimmy is usually experienced near 64 km/h (40 mph) and can begin or be amplified when the tire contacts pot holes or irregularities in the road surface.

Nibble

Sometimes confused with shimmy, nibble is a condition resulting from tire interaction with various road surfaces and observed by the driver as small rotational oscillations of the steering wheel.

Poor Return/Sticky Steering

Poor return and sticky steering is used to describe the poor return of the steering wheel to center after a turn or a steering correction.

Drift/Pull

Pull is a tugging sensation, felt by the hands on the steering wheel, that must be overcome to keep the vehicle going straight.

Drift describes what a vehicle with this condition does with hands off the steering wheel.

- A vehicle-related drift/pull, on a flat road, will cause a consistent deviation from the straight-ahead path and require constant steering input in the opposite direction to counteract the effect.

- Drift/pull may be induced by conditions external to the vehicle (for example, wind or road camber).

Poor Groove Feel

Poor groove feel is characterized by little or no buildup of turning effort felt in the steering wheel as the wheel is rocked slowly left and right within very small turns around center or straight-ahead (under 20 degrees of steering wheel turn). Efforts may be said to be "flat on center".

- In the diagnosis of a driveability problem, it is important to understand the difference between wander and poor groove feel.