During an alignment, what could cause caster to be below specification?

Caster is the angle formed by the steering axis in relation to vertical, as viewed from the side of the vehicle. When caster is below specification, it can negatively affect vehicle handling, particularly in terms of steering stability. One of the primary factors that influence caster settings is the vehicle's ride height, particularly at the front.

If the front ride height setting is incorrect, it can lead to an undesirable caster angle, as the geometry of the suspension components will change with variations in height. When the vehicle is lowered, for instance, the steering axis can tilt backward, reducing the positive caster angle, which results in compromised handling characteristics.

In contrast, while incorrect rear ride height can affect other suspension parameters and overall vehicle dynamics, it does not have a direct impact on the front caster angle. A malfunctioning strut assembly can also affect wheel alignment but typically does not lead to decreased caster specification on its own. An upgraded suspension system can be designed to modify caster angles, but unless specifically adjusted for effects on caster, it is not inherently the cause of decreased caster specification.

Understanding how ride height relates to caster settings is critical when diagnosing alignment issues, emphasizing the significant impact of front ride height on achieving proper caster.